systemd.exec

SYSTEMD.EXEC(5)                   systemd.exec                   SYSTEMD.EXEC(5)



NAME
       systemd.exec - Execution environment configuration

SYNOPSIS
       service.service, socket.socket, mount.mount, swap.swap

DESCRIPTION
       Unit configuration files for services, sockets, mount points, and swap
       devices share a subset of configuration options which define the
       execution environment of spawned processes.

       This man page lists the configuration options shared by these four unit
       types. See systemd.unit(5) for the common options of all unit
       configuration files, and systemd.service(5), systemd.socket(5),
       systemd.swap(5), and systemd.mount(5) for more information on the
       specific unit configuration files. The execution specific configuration
       options are configured in the [Service], [Socket], [Mount], or [Swap]
       sections, depending on the unit type.

       In addition, options which control resources through Linux Control Groups
       (cgroups) are listed in systemd.resource-control(5). Those options
       complement options listed here.

IMPLICIT DEPENDENCIES
       A few execution parameters result in additional, automatic dependencies
       to be added:

       •   Units with WorkingDirectory=, RootDirectory=, RootImage=,
           RuntimeDirectory=, StateDirectory=, CacheDirectory=, LogsDirectory=
           or ConfigurationDirectory= set automatically gain dependencies of
           type Requires= and After= on all mount units required to access the
           specified paths. This is equivalent to having them listed explicitly
           in RequiresMountsFor=.

       •   Similarly, units with PrivateTmp= enabled automatically get mount
           unit dependencies for all mounts required to access /tmp/ and
           /var/tmp/. They will also gain an automatic After= dependency on
           systemd-tmpfiles-setup.service(8).

       •   Units whose standard output or error output is connected to journal
           or kmsg (or their combinations with console output, see below)
           automatically acquire dependencies of type After= on
           systemd-journald.socket.

       •   Units using LogNamespace= will automatically gain ordering and
           requirement dependencies on the two socket units associated with
           systemd-journald@.service instances.

PATHS
       The following settings may be used to change a service's view of the
       filesystem. Please note that the paths must be absolute and must not
       contain a ".."  path component.

       WorkingDirectory=
           Takes a directory path relative to the service's root directory
           specified by RootDirectory=, or the special value "~". Sets the
           working directory for executed processes. If set to "~", the home
           directory of the user specified in User= is used. If not set,
           defaults to the root directory when systemd is running as a system
           instance and the respective user's home directory if run as user. If
           the setting is prefixed with the "-" character, a missing working
           directory is not considered fatal. If RootDirectory=/RootImage= is
           not set, then WorkingDirectory= is relative to the root of the system
           running the service manager. Note that setting this parameter might
           result in additional dependencies to be added to the unit (see
           above).

       RootDirectory=
           Takes a directory path relative to the host's root directory (i.e.
           the root of the system running the service manager). Sets the root
           directory for executed processes, with the chroot(2) system call. If
           this is used, it must be ensured that the process binary and all its
           auxiliary files are available in the chroot() jail. Note that setting
           this parameter might result in additional dependencies to be added to
           the unit (see above).

           The MountAPIVFS= and PrivateUsers= settings are particularly useful
           in conjunction with RootDirectory=. For details, see below.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RootImage=
           Takes a path to a block device node or regular file as argument. This
           call is similar to RootDirectory= however mounts a file system
           hierarchy from a block device node or loopback file instead of a
           directory. The device node or file system image file needs to contain
           a file system without a partition table, or a file system within an
           MBR/MS-DOS or GPT partition table with only a single Linux-compatible
           partition, or a set of file systems within a GPT partition table that
           follows the Discoverable Partitions Specification[1].

           When DevicePolicy= is set to "closed" or "strict", or set to "auto"
           and DeviceAllow= is set, then this setting adds /dev/loop-control
           with rw mode, "block-loop" and "block-blkext" with rwm mode to
           DeviceAllow=. See systemd.resource-control(5) for the details about
           DevicePolicy= or DeviceAllow=. Also, see PrivateDevices= below, as it
           may change the setting of DevicePolicy=.

           Units making use of RootImage= automatically gain an After=
           dependency on systemd-udevd.service.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RootImageOptions=
           Takes a comma-separated list of mount options that will be used on
           disk images specified by RootImage=. Optionally a partition name can
           be prefixed, followed by colon, in case the image has multiple
           partitions, otherwise partition name "root" is implied. Options for
           multiple partitions can be specified in a single line with space
           separators. Assigning an empty string removes previous assignments.
           Duplicated options are ignored. For a list of valid mount options,
           please refer to mount(8).

           Valid partition names follow the Discoverable Partitions
           Specification[1].

           Table 1. Accepted partition names
           ┌───────────────┐
           │Partition Name │
           ├───────────────┤
           │root           │
           ├───────────────┤
           │root-secondary │
           ├───────────────┤
           │home           │
           ├───────────────┤
           │srv            │
           ├───────────────┤
           │esp            │
           ├───────────────┤
           │xbootldr       │
           ├───────────────┤
           │tmp            │
           ├───────────────┤
           │var            │
           ├───────────────┤
           │usr            │
           └───────────────┘
           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RootHash=
           Takes a data integrity (dm-verity) root hash specified in
           hexadecimal, or the path to a file containing a root hash in ASCII
           hexadecimal format. This option enables data integrity checks using
           dm-verity, if the used image contains the appropriate integrity data
           (see above) or if RootVerity= is used. The specified hash must match
           the root hash of integrity data, and is usually at least 256 bits
           (and hence 64 formatted hexadecimal characters) long (in case of
           SHA256 for example). If this option is not specified, but the image
           file carries the "user.verity.roothash" extended file attribute (see
           xattr(7)), then the root hash is read from it, also as formatted
           hexadecimal characters. If the extended file attribute is not found
           (or is not supported by the underlying file system), but a file with
           the .roothash suffix is found next to the image file, bearing
           otherwise the same name (except if the image has the .raw suffix, in
           which case the root hash file must not have it in its name), the root
           hash is read from it and automatically used, also as formatted
           hexadecimal characters.

           If the disk image contains a separate /usr/ partition it may also be
           Verity protected, in which case the root hash may configured via an
           extended attribute "user.verity.usrhash" or a .usrhash file adjacent
           to the disk image. There's currently no option to configure the root
           hash for the /usr/ file system via the unit file directly.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RootHashSignature=
           Takes a PKCS7 signature of the RootHash= option as a path to a
           DER-encoded signature file, or as an ASCII base64 string encoding of
           a DER-encoded signature prefixed by "base64:". The dm-verity volume
           will only be opened if the signature of the root hash is valid and
           signed by a public key present in the kernel keyring. If this option
           is not specified, but a file with the .roothash.p7s suffix is found
           next to the image file, bearing otherwise the same name (except if
           the image has the .raw suffix, in which case the signature file must
           not have it in its name), the signature is read from it and
           automatically used.

           If the disk image contains a separate /usr/ partition it may also be
           Verity protected, in which case the signature for the root hash may
           configured via a .usrhash.p7s file adjacent to the disk image.
           There's currently no option to configure the root hash signature for
           the /usr/ via the unit file directly.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RootVerity=
           Takes the path to a data integrity (dm-verity) file. This option
           enables data integrity checks using dm-verity, if RootImage= is used
           and a root-hash is passed and if the used image itself does not
           contains the integrity data. The integrity data must be matched by
           the root hash. If this option is not specified, but a file with the
           .verity suffix is found next to the image file, bearing otherwise the
           same name (except if the image has the .raw suffix, in which case the
           verity data file must not have it in its name), the verity data is
           read from it and automatically used.

           This option is supported only for disk images that contain a single
           file system, without an enveloping partition table. Images that
           contain a GPT partition table should instead include both root file
           system and matching Verity data in the same image, implementing the
           Discoverable Partition Specification[1].

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       MountAPIVFS=
           Takes a boolean argument. If on, a private mount namespace for the
           unit's processes is created and the API file systems /proc/, /sys/,
           and /dev/ are mounted inside of it, unless they are already mounted.
           Note that this option has no effect unless used in conjunction with
           RootDirectory=/RootImage= as these three mounts are generally mounted
           in the host anyway, and unless the root directory is changed, the
           private mount namespace will be a 1:1 copy of the host's, and include
           these three mounts. Note that the /dev/ file system of the host is
           bind mounted if this option is used without PrivateDevices=. To run
           the service with a private, minimal version of /dev/, combine this
           option with PrivateDevices=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectProc=
           Takes one of "noaccess", "invisible", "ptraceable" or "default"
           (which it defaults to). When set, this controls the "hidepid=" mount
           option of the "procfs" instance for the unit that controls which
           directories with process metainformation (/proc/PID) are visible and
           accessible: when set to "noaccess" the ability to access most of
           other users' process metadata in /proc/ is taken away for processes
           of the service. When set to "invisible" processes owned by other
           users are hidden from /proc/. If "ptraceable" all processes that
           cannot be ptrace()'ed by a process are hidden to it. If "default" no
           restrictions on /proc/ access or visibility are made. For further
           details see The /proc Filesystem[2]. It is generally recommended to
           run most system services with this option set to "invisible". This
           option is implemented via file system namespacing, and thus cannot be
           used with services that shall be able to install mount points in the
           host file system hierarchy. It also cannot be used for services that
           need to access metainformation about other users' processes. This
           option implies MountAPIVFS=.

           If the kernel doesn't support per-mount point hidepid= mount options
           this setting remains without effect, and the unit's processes will be
           able to access and see other process as if the option was not used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProcSubset=
           Takes one of "all" (the default) and "pid". If the latter all files
           and directories not directly associated with process management and
           introspection are made invisible in the /proc/ file system configured
           for the unit's processes. This controls the "subset=" mount option of
           the "procfs" instance for the unit. For further details see The /proc
           Filesystem[2]. Note that Linux exposes various kernel APIs via
           /proc/, which are made unavailable with this setting. Since these
           APIs are used frequently this option is useful only in a few,
           specific cases, and is not suitable for most non-trivial programs.

           Much like ProtectProc= above, this is implemented via file system
           mount namespacing, and hence the same restrictions apply: it is only
           available to system services, it disables mount propagation to the
           host mount table, and it implies MountAPIVFS=. Also, like
           ProtectProc= this setting is gracefully disabled if the used kernel
           does not support the "subset=" mount option of "procfs".

       BindPaths=, BindReadOnlyPaths=
           Configures unit-specific bind mounts. A bind mount makes a particular
           file or directory available at an additional place in the unit's view
           of the file system. Any bind mounts created with this option are
           specific to the unit, and are not visible in the host's mount table.
           This option expects a whitespace separated list of bind mount
           definitions. Each definition consists of a colon-separated triple of
           source path, destination path and option string, where the latter two
           are optional. If only a source path is specified the source and
           destination is taken to be the same. The option string may be either
           "rbind" or "norbind" for configuring a recursive or non-recursive
           bind mount. If the destination path is omitted, the option string
           must be omitted too. Each bind mount definition may be prefixed with
           "-", in which case it will be ignored when its source path does not
           exist.

           BindPaths= creates regular writable bind mounts (unless the source
           file system mount is already marked read-only), while
           BindReadOnlyPaths= creates read-only bind mounts. These settings may
           be used more than once, each usage appends to the unit's list of bind
           mounts. If the empty string is assigned to either of these two
           options the entire list of bind mounts defined prior to this is
           reset. Note that in this case both read-only and regular bind mounts
           are reset, regardless which of the two settings is used.

           This option is particularly useful when RootDirectory=/RootImage= is
           used. In this case the source path refers to a path on the host file
           system, while the destination path refers to a path below the root
           directory of the unit.

           Note that the destination directory must exist or systemd must be
           able to create it. Thus, it is not possible to use those options for
           mount points nested underneath paths specified in InaccessiblePaths=,
           or under /home/ and other protected directories if ProtectHome=yes is
           specified.  TemporaryFileSystem= with ":ro" or ProtectHome=tmpfs
           should be used instead.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       MountImages=
           This setting is similar to RootImage= in that it mounts a file system
           hierarchy from a block device node or loopback file, but the
           destination directory can be specified as well as mount options. This
           option expects a whitespace separated list of mount definitions. Each
           definition consists of a colon-separated tuple of source path and
           destination definitions, optionally followed by another colon and a
           list of mount options.

           Mount options may be defined as a single comma-separated list of
           options, in which case they will be implicitly applied to the root
           partition on the image, or a series of colon-separated tuples of
           partition name and mount options. Valid partition names and mount
           options are the same as for RootImageOptions= setting described
           above.

           Each mount definition may be prefixed with "-", in which case it will
           be ignored when its source path does not exist. The source argument
           is a path to a block device node or regular file. If source or
           destination contain a ":", it needs to be escaped as "\:". The device
           node or file system image file needs to follow the same rules as
           specified for RootImage=. Any mounts created with this option are
           specific to the unit, and are not visible in the host's mount table.

           These settings may be used more than once, each usage appends to the
           unit's list of mount paths. If the empty string is assigned, the
           entire list of mount paths defined prior to this is reset.

           Note that the destination directory must exist or systemd must be
           able to create it. Thus, it is not possible to use those options for
           mount points nested underneath paths specified in InaccessiblePaths=,
           or under /home/ and other protected directories if ProtectHome=yes is
           specified.

           When DevicePolicy= is set to "closed" or "strict", or set to "auto"
           and DeviceAllow= is set, then this setting adds /dev/loop-control
           with rw mode, "block-loop" and "block-blkext" with rwm mode to
           DeviceAllow=. See systemd.resource-control(5) for the details about
           DevicePolicy= or DeviceAllow=. Also, see PrivateDevices= below, as it
           may change the setting of DevicePolicy=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

CREDENTIALS
       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       User=, Group=
           Set the UNIX user or group that the processes are executed as,
           respectively. Takes a single user or group name, or a numeric ID as
           argument. For system services (services run by the system service
           manager, i.e. managed by PID 1) and for user services of the root
           user (services managed by root's instance of systemd --user), the
           default is "root", but User= may be used to specify a different user.
           For user services of any other user, switching user identity is not
           permitted, hence the only valid setting is the same user the user's
           service manager is running as. If no group is set, the default group
           of the user is used. This setting does not affect commands whose
           command line is prefixed with "+".

           Note that this enforces only weak restrictions on the user/group name
           syntax, but will generate warnings in many cases where user/group
           names do not adhere to the following rules: the specified name should
           consist only of the characters a-z, A-Z, 0-9, "_" and "-", except for
           the first character which must be one of a-z, A-Z and "_" (i.e.
           digits and "-" are not permitted as first character). The user/group
           name must have at least one character, and at most 31. These
           restrictions are made in order to avoid ambiguities and to ensure
           user/group names and unit files remain portable among Linux systems.
           For further details on the names accepted and the names warned about
           see User/Group Name Syntax[3].

           When used in conjunction with DynamicUser= the user/group name
           specified is dynamically allocated at the time the service is
           started, and released at the time the service is stopped — unless it
           is already allocated statically (see below). If DynamicUser= is not
           used the specified user and group must have been created statically
           in the user database no later than the moment the service is started,
           for example using the sysusers.d(5) facility, which is applied at
           boot or package install time. If the user does not exist by then
           program invocation will fail.

           If the User= setting is used the supplementary group list is
           initialized from the specified user's default group list, as defined
           in the system's user and group database. Additional groups may be
           configured through the SupplementaryGroups= setting (see below).

       DynamicUser=
           Takes a boolean parameter. If set, a UNIX user and group pair is
           allocated dynamically when the unit is started, and released as soon
           as it is stopped. The user and group will not be added to /etc/passwd
           or /etc/group, but are managed transiently during runtime. The nss-
           systemd(8) glibc NSS module provides integration of these dynamic
           users/groups into the system's user and group databases. The user and
           group name to use may be configured via User= and Group= (see above).
           If these options are not used and dynamic user/group allocation is
           enabled for a unit, the name of the dynamic user/group is implicitly
           derived from the unit name. If the unit name without the type suffix
           qualifies as valid user name it is used directly, otherwise a name
           incorporating a hash of it is used. If a statically allocated user or
           group of the configured name already exists, it is used and no
           dynamic user/group is allocated. Note that if User= is specified and
           the static group with the name exists, then it is required that the
           static user with the name already exists. Similarly, if Group= is
           specified and the static user with the name exists, then it is
           required that the static group with the name already exists. Dynamic
           users/groups are allocated from the UID/GID range 61184...65519. It
           is recommended to avoid this range for regular system or login users.
           At any point in time each UID/GID from this range is only assigned to
           zero or one dynamically allocated users/groups in use. However,
           UID/GIDs are recycled after a unit is terminated. Care should be
           taken that any processes running as part of a unit for which dynamic
           users/groups are enabled do not leave files or directories owned by
           these users/groups around, as a different unit might get the same
           UID/GID assigned later on, and thus gain access to these files or
           directories. If DynamicUser= is enabled, RemoveIPC= and PrivateTmp=
           are implied (and cannot be turned off). This ensures that the
           lifetime of IPC objects and temporary files created by the executed
           processes is bound to the runtime of the service, and hence the
           lifetime of the dynamic user/group. Since /tmp/ and /var/tmp/ are
           usually the only world-writable directories on a system this ensures
           that a unit making use of dynamic user/group allocation cannot leave
           files around after unit termination. Furthermore NoNewPrivileges= and
           RestrictSUIDSGID= are implicitly enabled (and cannot be disabled), to
           ensure that processes invoked cannot take benefit or create SUID/SGID
           files or directories. Moreover ProtectSystem=strict and
           ProtectHome=read-only are implied, thus prohibiting the service to
           write to arbitrary file system locations. In order to allow the
           service to write to certain directories, they have to be allow-listed
           using ReadWritePaths=, but care must be taken so that UID/GID
           recycling doesn't create security issues involving files created by
           the service. Use RuntimeDirectory= (see below) in order to assign a
           writable runtime directory to a service, owned by the dynamic
           user/group and removed automatically when the unit is terminated. Use
           StateDirectory=, CacheDirectory= and LogsDirectory= in order to
           assign a set of writable directories for specific purposes to the
           service in a way that they are protected from vulnerabilities due to
           UID reuse (see below). If this option is enabled, care should be
           taken that the unit's processes do not get access to directories
           outside of these explicitly configured and managed ones.
           Specifically, do not use BindPaths= and be careful with AF_UNIX file
           descriptor passing for directory file descriptors, as this would
           permit processes to create files or directories owned by the dynamic
           user/group that are not subject to the lifecycle and access
           guarantees of the service. Defaults to off.

       SupplementaryGroups=
           Sets the supplementary Unix groups the processes are executed as.
           This takes a space-separated list of group names or IDs. This option
           may be specified more than once, in which case all listed groups are
           set as supplementary groups. When the empty string is assigned, the
           list of supplementary groups is reset, and all assignments prior to
           this one will have no effect. In any way, this option does not
           override, but extends the list of supplementary groups configured in
           the system group database for the user. This does not affect commands
           prefixed with "+".

       PAMName=
           Sets the PAM service name to set up a session as. If set, the
           executed process will be registered as a PAM session under the
           specified service name. This is only useful in conjunction with the
           User= setting, and is otherwise ignored. If not set, no PAM session
           will be opened for the executed processes. See pam(8) for details.

           Note that for each unit making use of this option a PAM session
           handler process will be maintained as part of the unit and stays
           around as long as the unit is active, to ensure that appropriate
           actions can be taken when the unit and hence the PAM session
           terminates. This process is named "(sd-pam)" and is an immediate
           child process of the unit's main process.

           Note that when this option is used for a unit it is very likely
           (depending on PAM configuration) that the main unit process will be
           migrated to its own session scope unit when it is activated. This
           process will hence be associated with two units: the unit it was
           originally started from (and for which PAMName= was configured), and
           the session scope unit. Any child processes of that process will
           however be associated with the session scope unit only. This has
           implications when used in combination with NotifyAccess=all, as these
           child processes will not be able to affect changes in the original
           unit through notification messages. These messages will be considered
           belonging to the session scope unit and not the original unit. It is
           hence not recommended to use PAMName= in combination with
           NotifyAccess=all.

CAPABILITIES
       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       CapabilityBoundingSet=
           Controls which capabilities to include in the capability bounding set
           for the executed process. See capabilities(7) for details. Takes a
           whitespace-separated list of capability names, e.g.  CAP_SYS_ADMIN,
           CAP_DAC_OVERRIDE, CAP_SYS_PTRACE. Capabilities listed will be
           included in the bounding set, all others are removed. If the list of
           capabilities is prefixed with "~", all but the listed capabilities
           will be included, the effect of the assignment inverted. Note that
           this option also affects the respective capabilities in the
           effective, permitted and inheritable capability sets. If this option
           is not used, the capability bounding set is not modified on process
           execution, hence no limits on the capabilities of the process are
           enforced. This option may appear more than once, in which case the
           bounding sets are merged by OR, or by AND if the lines are prefixed
           with "~" (see below). If the empty string is assigned to this option,
           the bounding set is reset to the empty capability set, and all prior
           settings have no effect. If set to "~" (without any further
           argument), the bounding set is reset to the full set of available
           capabilities, also undoing any previous settings. This does not
           affect commands prefixed with "+".

           Use systemd-analyze(1)'s capability command to retrieve a list of
           capabilities defined on the local system.

           Example: if a unit has the following,

               CapabilityBoundingSet=CAP_A CAP_B
               CapabilityBoundingSet=CAP_B CAP_C

           then CAP_A, CAP_B, and CAP_C are set. If the second line is prefixed
           with "~", e.g.,

               CapabilityBoundingSet=CAP_A CAP_B
               CapabilityBoundingSet=~CAP_B CAP_C

           then, only CAP_A is set.

       AmbientCapabilities=
           Controls which capabilities to include in the ambient capability set
           for the executed process. Takes a whitespace-separated list of
           capability names, e.g.  CAP_SYS_ADMIN, CAP_DAC_OVERRIDE,
           CAP_SYS_PTRACE. This option may appear more than once in which case
           the ambient capability sets are merged (see the above examples in
           CapabilityBoundingSet=). If the list of capabilities is prefixed with
           "~", all but the listed capabilities will be included, the effect of
           the assignment inverted. If the empty string is assigned to this
           option, the ambient capability set is reset to the empty capability
           set, and all prior settings have no effect. If set to "~" (without
           any further argument), the ambient capability set is reset to the
           full set of available capabilities, also undoing any previous
           settings. Note that adding capabilities to ambient capability set
           adds them to the process's inherited capability set.

           Ambient capability sets are useful if you want to execute a process
           as a non-privileged user but still want to give it some capabilities.
           Note that in this case option keep-caps is automatically added to
           SecureBits= to retain the capabilities over the user change.
           AmbientCapabilities= does not affect commands prefixed with "+".

SECURITY
       NoNewPrivileges=
           Takes a boolean argument. If true, ensures that the service process
           and all its children can never gain new privileges through execve()
           (e.g. via setuid or setgid bits, or filesystem capabilities). This is
           the simplest and most effective way to ensure that a process and its
           children can never elevate privileges again. Defaults to false, but
           certain settings override this and ignore the value of this setting.
           This is the case when SystemCallFilter=, SystemCallArchitectures=,
           RestrictAddressFamilies=, RestrictNamespaces=, PrivateDevices=,
           ProtectKernelTunables=, ProtectKernelModules=, ProtectKernelLogs=,
           ProtectClock=, MemoryDenyWriteExecute=, RestrictRealtime=,
           RestrictSUIDSGID=, DynamicUser= or LockPersonality= are specified.
           Note that even if this setting is overridden by them, systemctl show
           shows the original value of this setting. Also see No New Privileges
           Flag[4].

       SecureBits=
           Controls the secure bits set for the executed process. Takes a
           space-separated combination of options from the following list:
           keep-caps, keep-caps-locked, no-setuid-fixup, no-setuid-fixup-locked,
           noroot, and noroot-locked. This option may appear more than once, in
           which case the secure bits are ORed. If the empty string is assigned
           to this option, the bits are reset to 0. This does not affect
           commands prefixed with "+". See capabilities(7) for details.

MANDATORY ACCESS CONTROL
       These options are only available for system services and are not
       supported for services running in per-user instances of the service
       manager.

       SELinuxContext=
           Set the SELinux security context of the executed process. If set,
           this will override the automated domain transition. However, the
           policy still needs to authorize the transition. This directive is
           ignored if SELinux is disabled. If prefixed by "-", all errors will
           be ignored. This does not affect commands prefixed with "+". See
           setexeccon(3) for details.

       AppArmorProfile=
           Takes a profile name as argument. The process executed by the unit
           will switch to this profile when started. Profiles must already be
           loaded in the kernel, or the unit will fail. If prefixed by "-", all
           errors will be ignored. This setting has no effect if AppArmor is not
           enabled. This setting does not affect commands prefixed with "+".

       SmackProcessLabel=
           Takes a SMACK64 security label as argument. The process executed by
           the unit will be started under this label and SMACK will decide
           whether the process is allowed to run or not, based on it. The
           process will continue to run under the label specified here unless
           the executable has its own SMACK64EXEC label, in which case the
           process will transition to run under that label. When not specified,
           the label that systemd is running under is used. This directive is
           ignored if SMACK is disabled.

           The value may be prefixed by "-", in which case all errors will be
           ignored. An empty value may be specified to unset previous
           assignments. This does not affect commands prefixed with "+".

PROCESS PROPERTIES
       LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=,
       LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=,
       LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=, LimitRTTIME=
           Set soft and hard limits on various resources for executed processes.
           See setrlimit(2) for details on the resource limit concept. Resource
           limits may be specified in two formats: either as single value to set
           a specific soft and hard limit to the same value, or as
           colon-separated pair soft:hard to set both limits individually (e.g.
           "LimitAS=4G:16G"). Use the string infinity to configure no limit on a
           specific resource. The multiplicative suffixes K, M, G, T, P and E
           (to the base 1024) may be used for resource limits measured in bytes
           (e.g.  "LimitAS=16G"). For the limits referring to time values, the
           usual time units ms, s, min, h and so on may be used (see
           systemd.time(7) for details). Note that if no time unit is specified
           for LimitCPU= the default unit of seconds is implied, while for
           LimitRTTIME= the default unit of microseconds is implied. Also, note
           that the effective granularity of the limits might influence their
           enforcement. For example, time limits specified for LimitCPU= will be
           rounded up implicitly to multiples of 1s. For LimitNICE= the value
           may be specified in two syntaxes: if prefixed with "+" or "-", the
           value is understood as regular Linux nice value in the range -20..19.
           If not prefixed like this the value is understood as raw resource
           limit parameter in the range 0..40 (with 0 being equivalent to 1).

           Note that most process resource limits configured with these options
           are per-process, and processes may fork in order to acquire a new set
           of resources that are accounted independently of the original
           process, and may thus escape limits set. Also note that LimitRSS= is
           not implemented on Linux, and setting it has no effect. Often it is
           advisable to prefer the resource controls listed in systemd.resource-
           control(5) over these per-process limits, as they apply to services
           as a whole, may be altered dynamically at runtime, and are generally
           more expressive. For example, MemoryMax= is a more powerful (and
           working) replacement for LimitRSS=.

           Resource limits not configured explicitly for a unit default to the
           value configured in the various DefaultLimitCPU=, DefaultLimitFSIZE=,
           ... options available in systemd-system.conf(5), and – if not
           configured there – the kernel or per-user defaults, as defined by the
           OS (the latter only for user services, see below).

           For system units these resource limits may be chosen freely. When
           these settings are configured in a user service (i.e. a service run
           by the per-user instance of the service manager) they cannot be used
           to raise the limits above those set for the user manager itself when
           it was first invoked, as the user's service manager generally lacks
           the privileges to do so. In user context these configuration options
           are hence only useful to lower the limits passed in or to raise the
           soft limit to the maximum of the hard limit as configured for the
           user. To raise the user's limits further, the available configuration
           mechanisms differ between operating systems, but typically require
           privileges. In most cases it is possible to configure higher per-user
           resource limits via PAM or by setting limits on the system service
           encapsulating the user's service manager, i.e. the user's instance of
           user@.service. After making such changes, make sure to restart the
           user's service manager.

           Table 2. Resource limit directives, their equivalent ulimit shell
           commands and the unit used
           ┌─────────────────┬───────────────────┬─────────────────────┐
           │Directive        ulimit equivalent │ Unit                │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitCPU=        │ ulimit -t         │ Seconds             │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitFSIZE=      │ ulimit -f         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitDATA=       │ ulimit -d         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitSTACK=      │ ulimit -s         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitCORE=       │ ulimit -c         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRSS=        │ ulimit -m         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNOFILE=     │ ulimit -n         │ Number of File      │
           │                 │                   │ Descriptors         │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitAS=         │ ulimit -v         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNPROC=      │ ulimit -u         │ Number of Processes │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitMEMLOCK=    │ ulimit -l         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitLOCKS=      │ ulimit -x         │ Number of Locks     │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitSIGPENDING= │ ulimit -i         │ Number of Queued    │
           │                 │                   │ Signals             │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitMSGQUEUE=   │ ulimit -q         │ Bytes               │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitNICE=       │ ulimit -e         │ Nice Level          │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRTPRIO=     │ ulimit -r         │ Realtime Priority   │
           ├─────────────────┼───────────────────┼─────────────────────┤
           │LimitRTTIME=     │ No equivalent     │ Microseconds        │
           └─────────────────┴───────────────────┴─────────────────────┘

       UMask=
           Controls the file mode creation mask. Takes an access mode in octal
           notation. See umask(2) for details. Defaults to 0022 for system
           units. For user units the default value is inherited from the
           per-user service manager (whose default is in turn inherited from the
           system service manager, and thus typically also is 0022 — unless
           overridden by a PAM module). In order to change the per-user mask for
           all user services, consider setting the UMask= setting of the user's
           user@.service system service instance. The per-user umask may also be
           set via the umask field of a user's JSON User Record[5] (for users
           managed by systemd-homed.service(8) this field may be controlled via
           homectl --umask=). It may also be set via a PAM module, such as
           pam_umask(8).

       CoredumpFilter=
           Controls which types of memory mappings will be saved if the process
           dumps core (using the /proc/pid/coredump_filter file). Takes a
           whitespace-separated combination of mapping type names or numbers
           (with the default base 16). Mapping type names are private-anonymous,
           shared-anonymous, private-file-backed, shared-file-backed,
           elf-headers, private-huge, shared-huge, private-dax, shared-dax, and
           the special values all (all types) and default (the kernel default of
           "private-anonymous shared-anonymous elf-headers private-huge"). See
           core(5) for the meaning of the mapping types. When specified multiple
           times, all specified masks are ORed. When not set, or if the empty
           value is assigned, the inherited value is not changed.

           Example 1. Add DAX pages to the dump filter

               CoredumpFilter=default private-dax shared-dax

       KeyringMode=
           Controls how the kernel session keyring is set up for the service
           (see session-keyring(7) for details on the session keyring). Takes
           one of inherit, private, shared. If set to inherit no special keyring
           setup is done, and the kernel's default behaviour is applied. If
           private is used a new session keyring is allocated when a service
           process is invoked, and it is not linked up with any user keyring.
           This is the recommended setting for system services, as this ensures
           that multiple services running under the same system user ID (in
           particular the root user) do not share their key material among each
           other. If shared is used a new session keyring is allocated as for
           private, but the user keyring of the user configured with User= is
           linked into it, so that keys assigned to the user may be requested by
           the unit's processes. In this modes multiple units running processes
           under the same user ID may share key material. Unless inherit is
           selected the unique invocation ID for the unit (see below) is added
           as a protected key by the name "invocation_id" to the newly created
           session keyring. Defaults to private for services of the system
           service manager and to inherit for non-service units and for services
           of the user service manager.

       OOMScoreAdjust=
           Sets the adjustment value for the Linux kernel's Out-Of-Memory (OOM)
           killer score for executed processes. Takes an integer between -1000
           (to disable OOM killing of processes of this unit) and 1000 (to make
           killing of processes of this unit under memory pressure very likely).
           See proc.txt[6] for details. If not specified defaults to the OOM
           score adjustment level of the service manager itself, which is
           normally at 0.

           Use the OOMPolicy= setting of service units to configure how the
           service manager shall react to the kernel OOM killer terminating a
           process of the service. See systemd.service(5) for details.

       TimerSlackNSec=
           Sets the timer slack in nanoseconds for the executed processes. The
           timer slack controls the accuracy of wake-ups triggered by timers.
           See prctl(2) for more information. Note that in contrast to most
           other time span definitions this parameter takes an integer value in
           nano-seconds if no unit is specified. The usual time units are
           understood too.

       Personality=
           Controls which kernel architecture uname(2) shall report, when
           invoked by unit processes. Takes one of the architecture identifiers
           x86, x86-64, ppc, ppc-le, ppc64, ppc64-le, s390 or s390x. Which
           personality architectures are supported depends on the system
           architecture. Usually the 64bit versions of the various system
           architectures support their immediate 32bit personality architecture
           counterpart, but no others. For example, x86-64 systems support the
           x86-64 and x86 personalities but no others. The personality feature
           is useful when running 32-bit services on a 64-bit host system. If
           not specified, the personality is left unmodified and thus reflects
           the personality of the host system's kernel.

       IgnoreSIGPIPE=
           Takes a boolean argument. If true, causes SIGPIPE to be ignored in
           the executed process. Defaults to true because SIGPIPE generally is
           useful only in shell pipelines.

SCHEDULING
       Nice=
           Sets the default nice level (scheduling priority) for executed
           processes. Takes an integer between -20 (highest priority) and 19
           (lowest priority). See setpriority(2) for details.

       CPUSchedulingPolicy=
           Sets the CPU scheduling policy for executed processes. Takes one of
           other, batch, idle, fifo or rr. See sched_setscheduler(2) for
           details.

       CPUSchedulingPriority=
           Sets the CPU scheduling priority for executed processes. The
           available priority range depends on the selected CPU scheduling
           policy (see above). For real-time scheduling policies an integer
           between 1 (lowest priority) and 99 (highest priority) can be used.
           See sched_setscheduler(2) for details.

       CPUSchedulingResetOnFork=
           Takes a boolean argument. If true, elevated CPU scheduling priorities
           and policies will be reset when the executed processes call fork(2),
           and can hence not leak into child processes. See
           sched_setscheduler(2) for details. Defaults to false.

       CPUAffinity=
           Controls the CPU affinity of the executed processes. Takes a list of
           CPU indices or ranges separated by either whitespace or commas.
           Alternatively, takes a special "numa" value in which case systemd
           automatically derives allowed CPU range based on the value of
           NUMAMask= option. CPU ranges are specified by the lower and upper CPU
           indices separated by a dash. This option may be specified more than
           once, in which case the specified CPU affinity masks are merged. If
           the empty string is assigned, the mask is reset, all assignments
           prior to this will have no effect. See sched_setaffinity(2) for
           details.

       NUMAPolicy=
           Controls the NUMA memory policy of the executed processes. Takes a
           policy type, one of: default, preferred, bind, interleave and local.
           A list of NUMA nodes that should be associated with the policy must
           be specified in NUMAMask=. For more details on each policy please
           see, set_mempolicy(2). For overall overview of NUMA support in Linux
           see, numa(7).

       NUMAMask=
           Controls the NUMA node list which will be applied alongside with
           selected NUMA policy. Takes a list of NUMA nodes and has the same
           syntax as a list of CPUs for CPUAffinity= option or special "all"
           value which will include all available NUMA nodes in the mask. Note
           that the list of NUMA nodes is not required for default and local
           policies and for preferred policy we expect a single NUMA node.

       IOSchedulingClass=
           Sets the I/O scheduling class for executed processes. Takes an
           integer between 0 and 3 or one of the strings none, realtime,
           best-effort or idle. If the empty string is assigned to this option,
           all prior assignments to both IOSchedulingClass= and
           IOSchedulingPriority= have no effect. See ioprio_set(2) for details.

       IOSchedulingPriority=
           Sets the I/O scheduling priority for executed processes. Takes an
           integer between 0 (highest priority) and 7 (lowest priority). The
           available priorities depend on the selected I/O scheduling class (see
           above). If the empty string is assigned to this option, all prior
           assignments to both IOSchedulingClass= and IOSchedulingPriority= have
           no effect. See ioprio_set(2) for details.

SANDBOXING
       The following sandboxing options are an effective way to limit the
       exposure of the system towards the unit's processes. It is recommended to
       turn on as many of these options for each unit as is possible without
       negatively affecting the process' ability to operate. Note that many of
       these sandboxing features are gracefully turned off on systems where the
       underlying security mechanism is not available. For example,
       ProtectSystem= has no effect if the kernel is built without file system
       namespacing or if the service manager runs in a container manager that
       makes file system namespacing unavailable to its payload. Similar,
       RestrictRealtime= has no effect on systems that lack support for SECCOMP
       system call filtering, or in containers where support for this is turned
       off.

       Also note that some sandboxing functionality is generally not available
       in user services (i.e. services run by the per-user service manager).
       Specifically, the various settings requiring file system namespacing
       support (such as ProtectSystem=) are not available, as the underlying
       kernel functionality is only accessible to privileged processes. However,
       most namespacing settings, that will not work on their own in user
       services, will work when used in conjunction with PrivateUsers=true.

       ProtectSystem=
           Takes a boolean argument or the special values "full" or "strict". If
           true, mounts the /usr/ and the boot loader directories (/boot and
           /efi) read-only for processes invoked by this unit. If set to "full",
           the /etc/ directory is mounted read-only, too. If set to "strict" the
           entire file system hierarchy is mounted read-only, except for the API
           file system subtrees /dev/, /proc/ and /sys/ (protect these
           directories using PrivateDevices=, ProtectKernelTunables=,
           ProtectControlGroups=). This setting ensures that any modification of
           the vendor-supplied operating system (and optionally its
           configuration, and local mounts) is prohibited for the service. It is
           recommended to enable this setting for all long-running services,
           unless they are involved with system updates or need to modify the
           operating system in other ways. If this option is used,
           ReadWritePaths= may be used to exclude specific directories from
           being made read-only. This setting is implied if DynamicUser= is set.
           This setting cannot ensure protection in all cases. In general it has
           the same limitations as ReadOnlyPaths=, see below. Defaults to off.

       ProtectHome=
           Takes a boolean argument or the special values "read-only" or
           "tmpfs". If true, the directories /home/, /root, and /run/user are
           made inaccessible and empty for processes invoked by this unit. If
           set to "read-only", the three directories are made read-only instead.
           If set to "tmpfs", temporary file systems are mounted on the three
           directories in read-only mode. The value "tmpfs" is useful to hide
           home directories not relevant to the processes invoked by the unit,
           while still allowing necessary directories to be made visible when
           listed in BindPaths= or BindReadOnlyPaths=.

           Setting this to "yes" is mostly equivalent to set the three
           directories in InaccessiblePaths=. Similarly, "read-only" is mostly
           equivalent to ReadOnlyPaths=, and "tmpfs" is mostly equivalent to
           TemporaryFileSystem= with ":ro".

           It is recommended to enable this setting for all long-running
           services (in particular network-facing ones), to ensure they cannot
           get access to private user data, unless the services actually require
           access to the user's private data. This setting is implied if
           DynamicUser= is set. This setting cannot ensure protection in all
           cases. In general it has the same limitations as ReadOnlyPaths=, see
           below.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RuntimeDirectory=, StateDirectory=, CacheDirectory=, LogsDirectory=,
       ConfigurationDirectory=
           These options take a whitespace-separated list of directory names.
           The specified directory names must be relative, and may not include
           "..". If set, when the unit is started, one or more directories by
           the specified names will be created (including their parents) below
           the locations defined in the following table. Also, the corresponding
           environment variable will be defined with the full paths of the
           directories. If multiple directories are set, then in the environment
           variable the paths are concatenated with colon (":").

           Table 3. Automatic directory creation and environment variables
           ┌────────────────────────┬────────────────┬───────────────────────┬──────────────────────────┐
           │Directory               Below path for Below path for        Environment              │
           │                        │ system units   user units            variable set             │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │RuntimeDirectory=       │ /run/          │ $XDG_RUNTIME_DIR      $RUNTIME_DIRECTORY       │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │StateDirectory=         │ /var/lib/      │ $XDG_CONFIG_HOME      $STATE_DIRECTORY         │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │CacheDirectory=         │ /var/cache/    │ $XDG_CACHE_HOME       $CACHE_DIRECTORY         │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │LogsDirectory=          │ /var/log/      │ $XDG_CONFIG_HOME/log/ │ $LOGS_DIRECTORY          │
           ├────────────────────────┼────────────────┼───────────────────────┼──────────────────────────┤
           │ConfigurationDirectory= │ /etc/          │ $XDG_CONFIG_HOME      $CONFIGURATION_DIRECTORY │
           └────────────────────────┴────────────────┴───────────────────────┴──────────────────────────┘
           In case of RuntimeDirectory= the innermost subdirectories are removed
           when the unit is stopped. It is possible to preserve the specified
           directories in this case if RuntimeDirectoryPreserve= is configured
           to restart or yes (see below). The directories specified with
           StateDirectory=, CacheDirectory=, LogsDirectory=,
           ConfigurationDirectory= are not removed when the unit is stopped.

           Except in case of ConfigurationDirectory=, the innermost specified
           directories will be owned by the user and group specified in User=
           and Group=. If the specified directories already exist and their
           owning user or group do not match the configured ones, all files and
           directories below the specified directories as well as the
           directories themselves will have their file ownership recursively
           changed to match what is configured. As an optimization, if the
           specified directories are already owned by the right user and group,
           files and directories below of them are left as-is, even if they do
           not match what is requested. The innermost specified directories will
           have their access mode adjusted to the what is specified in
           RuntimeDirectoryMode=, StateDirectoryMode=, CacheDirectoryMode=,
           LogsDirectoryMode= and ConfigurationDirectoryMode=.

           These options imply BindPaths= for the specified paths. When combined
           with RootDirectory= or RootImage= these paths always reside on the
           host and are mounted from there into the unit's file system
           namespace.

           If DynamicUser= is used in conjunction with StateDirectory=, the
           logic for CacheDirectory= and LogsDirectory= is slightly altered: the
           directories are created below /var/lib/private, /var/cache/private
           and /var/log/private, respectively, which are host directories made
           inaccessible to unprivileged users, which ensures that access to
           these directories cannot be gained through dynamic user ID recycling.
           Symbolic links are created to hide this difference in behaviour. Both
           from perspective of the host and from inside the unit, the relevant
           directories hence always appear directly below /var/lib, /var/cache
           and /var/log.

           Use RuntimeDirectory= to manage one or more runtime directories for
           the unit and bind their lifetime to the daemon runtime. This is
           particularly useful for unprivileged daemons that cannot create
           runtime directories in /run/ due to lack of privileges, and to make
           sure the runtime directory is cleaned up automatically after use. For
           runtime directories that require more complex or different
           configuration or lifetime guarantees, please consider using
           tmpfiles.d(5).

           The directories defined by these options are always created under the
           standard paths used by systemd (/var/, /run/, /etc/, ...). If the
           service needs directories in a different location, a different
           mechanism has to be used to create them.

           tmpfiles.d(5) provides functionality that overlaps with these
           options. Using these options is recommended, because the lifetime of
           the directories is tied directly to the lifetime of the unit, and it
           is not necessary to ensure that the tmpfiles.d configuration is
           executed before the unit is started.

           To remove any of the directories created by these settings, use the
           systemctl clean ...  command on the relevant units, see systemctl(1)
           for details.

           Example: if a system service unit has the following,

               RuntimeDirectory=foo/bar baz

           the service manager creates /run/foo (if it does not exist),
           /run/foo/bar, and /run/baz. The directories /run/foo/bar and /run/baz
           except /run/foo are owned by the user and group specified in User=
           and Group=, and removed when the service is stopped.

           Example: if a system service unit has the following,

               RuntimeDirectory=foo/bar
               StateDirectory=aaa/bbb ccc

           then the environment variable "RUNTIME_DIRECTORY" is set with
           "/run/foo/bar", and "STATE_DIRECTORY" is set with
           "/var/lib/aaa/bbb:/var/lib/ccc".

       RuntimeDirectoryMode=, StateDirectoryMode=, CacheDirectoryMode=,
       LogsDirectoryMode=, ConfigurationDirectoryMode=
           Specifies the access mode of the directories specified in
           RuntimeDirectory=, StateDirectory=, CacheDirectory=, LogsDirectory=,
           or ConfigurationDirectory=, respectively, as an octal number.
           Defaults to 0755. See "Permissions" in path_resolution(7) for a
           discussion of the meaning of permission bits.

       RuntimeDirectoryPreserve=
           Takes a boolean argument or restart. If set to no (the default), the
           directories specified in RuntimeDirectory= are always removed when
           the service stops. If set to restart the directories are preserved
           when the service is both automatically and manually restarted. Here,
           the automatic restart means the operation specified in Restart=, and
           manual restart means the one triggered by systemctl restart
           foo.service. If set to yes, then the directories are not removed when
           the service is stopped. Note that since the runtime directory /run/
           is a mount point of "tmpfs", then for system services the directories
           specified in RuntimeDirectory= are removed when the system is
           rebooted.

       TimeoutCleanSec=
           Configures a timeout on the clean-up operation requested through
           systemctl clean ..., see systemctl(1) for details. Takes the usual
           time values and defaults to infinity, i.e. by default no timeout is
           applied. If a timeout is configured the clean operation will be
           aborted forcibly when the timeout is reached, potentially leaving
           resources on disk.

       ReadWritePaths=, ReadOnlyPaths=, InaccessiblePaths=
           Sets up a new file system namespace for executed processes. These
           options may be used to limit access a process has to the file system.
           Each setting takes a space-separated list of paths relative to the
           host's root directory (i.e. the system running the service manager).
           Note that if paths contain symlinks, they are resolved relative to
           the root directory set with RootDirectory=/RootImage=.

           Paths listed in ReadWritePaths= are accessible from within the
           namespace with the same access modes as from outside of it. Paths
           listed in ReadOnlyPaths= are accessible for reading only, writing
           will be refused even if the usual file access controls would permit
           this. Nest ReadWritePaths= inside of ReadOnlyPaths= in order to
           provide writable subdirectories within read-only directories. Use
           ReadWritePaths= in order to allow-list specific paths for write
           access if ProtectSystem=strict is used.

           Paths listed in InaccessiblePaths= will be made inaccessible for
           processes inside the namespace along with everything below them in
           the file system hierarchy. This may be more restrictive than desired,
           because it is not possible to nest ReadWritePaths=, ReadOnlyPaths=,
           BindPaths=, or BindReadOnlyPaths= inside it. For a more flexible
           option, see TemporaryFileSystem=.

           Non-directory paths may be specified as well. These options may be
           specified more than once, in which case all paths listed will have
           limited access from within the namespace. If the empty string is
           assigned to this option, the specific list is reset, and all prior
           assignments have no effect.

           Paths in ReadWritePaths=, ReadOnlyPaths= and InaccessiblePaths= may
           be prefixed with "-", in which case they will be ignored when they do
           not exist. If prefixed with "+" the paths are taken relative to the
           root directory of the unit, as configured with
           RootDirectory=/RootImage=, instead of relative to the root directory
           of the host (see above). When combining "-" and "+" on the same path
           make sure to specify "-" first, and "+" second.

           Note that these settings will disconnect propagation of mounts from
           the unit's processes to the host. This means that this setting may
           not be used for services which shall be able to install mount points
           in the main mount namespace. For ReadWritePaths= and ReadOnlyPaths=
           propagation in the other direction is not affected, i.e. mounts
           created on the host generally appear in the unit processes'
           namespace, and mounts removed on the host also disappear there too.
           In particular, note that mount propagation from host to unit will
           result in unmodified mounts to be created in the unit's namespace,
           i.e. writable mounts appearing on the host will be writable in the
           unit's namespace too, even when propagated below a path marked with
           ReadOnlyPaths=! Restricting access with these options hence does not
           extend to submounts of a directory that are created later on. This
           means the lock-down offered by that setting is not complete, and does
           not offer full protection.

           Note that the effect of these settings may be undone by privileged
           processes. In order to set up an effective sandboxed environment for
           a unit it is thus recommended to combine these settings with either
           CapabilityBoundingSet=~CAP_SYS_ADMIN or SystemCallFilter=~@mount.

           These options are only available for system services and are not
           supported for services running in per-user instances of the service
           manager.

       TemporaryFileSystem=
           Takes a space-separated list of mount points for temporary file
           systems (tmpfs). If set, a new file system namespace is set up for
           executed processes, and a temporary file system is mounted on each
           mount point. This option may be specified more than once, in which
           case temporary file systems are mounted on all listed mount points.
           If the empty string is assigned to this option, the list is reset,
           and all prior assignments have no effect. Each mount point may
           optionally be suffixed with a colon (":") and mount options such as
           "size=10%" or "ro". By default, each temporary file system is mounted
           with "nodev,strictatime,mode=0755". These can be disabled by
           explicitly specifying the corresponding mount options, e.g., "dev" or
           "nostrictatime".

           This is useful to hide files or directories not relevant to the
           processes invoked by the unit, while necessary files or directories
           can be still accessed by combining with BindPaths= or
           BindReadOnlyPaths=:

           Example: if a unit has the following,

               TemporaryFileSystem=/var:ro
               BindReadOnlyPaths=/var/lib/systemd

           then the invoked processes by the unit cannot see any files or
           directories under /var/ except for /var/lib/systemd or its contents.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       PrivateTmp=
           Takes a boolean argument. If true, sets up a new file system
           namespace for the executed processes and mounts private /tmp/ and
           /var/tmp/ directories inside it that are not shared by processes
           outside of the namespace. This is useful to secure access to
           temporary files of the process, but makes sharing between processes
           via /tmp/ or /var/tmp/ impossible. If this is enabled, all temporary
           files created by a service in these directories will be removed after
           the service is stopped. Defaults to false. It is possible to run two
           or more units within the same private /tmp/ and /var/tmp/ namespace
           by using the JoinsNamespaceOf= directive, see systemd.unit(5) for
           details. This setting is implied if DynamicUser= is set. For this
           setting the same restrictions regarding mount propagation and
           privileges apply as for ReadOnlyPaths= and related calls, see above.
           Enabling this setting has the side effect of adding Requires= and
           After= dependencies on all mount units necessary to access /tmp/ and
           /var/tmp/. Moreover an implicitly After= ordering on systemd-
           tmpfiles-setup.service(8) is added.

           Note that the implementation of this setting might be impossible (for
           example if mount namespaces are not available), and the unit should
           be written in a way that does not solely rely on this setting for
           security.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       PrivateDevices=
           Takes a boolean argument. If true, sets up a new /dev/ mount for the
           executed processes and only adds API pseudo devices such as
           /dev/null, /dev/zero or /dev/random (as well as the pseudo TTY
           subsystem) to it, but no physical devices such as /dev/sda, system
           memory /dev/mem, system ports /dev/port and others. This is useful to
           securely turn off physical device access by the executed process.
           Defaults to false. Enabling this option will install a system call
           filter to block low-level I/O system calls that are grouped in the
           @raw-io set, will also remove CAP_MKNOD and CAP_SYS_RAWIO from the
           capability bounding set for the unit (see above), and set
           DevicePolicy=closed (see systemd.resource-control(5) for details).
           Note that using this setting will disconnect propagation of mounts
           from the service to the host (propagation in the opposite direction
           continues to work). This means that this setting may not be used for
           services which shall be able to install mount points in the main
           mount namespace. The new /dev/ will be mounted read-only and
           'noexec'. The latter may break old programs which try to set up
           executable memory by using mmap(2) of /dev/zero instead of using
           MAP_ANON. For this setting the same restrictions regarding mount
           propagation and privileges apply as for ReadOnlyPaths= and related
           calls, see above. If turned on and if running in user mode, or in
           system mode, but without the CAP_SYS_ADMIN capability (e.g. setting
           User=), NoNewPrivileges=yes is implied.

           Note that the implementation of this setting might be impossible (for
           example if mount namespaces are not available), and the unit should
           be written in a way that does not solely rely on this setting for
           security.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       PrivateNetwork=
           Takes a boolean argument. If true, sets up a new network namespace
           for the executed processes and configures only the loopback network
           device "lo" inside it. No other network devices will be available to
           the executed process. This is useful to turn off network access by
           the executed process. Defaults to false. It is possible to run two or
           more units within the same private network namespace by using the
           JoinsNamespaceOf= directive, see systemd.unit(5) for details. Note
           that this option will disconnect all socket families from the host,
           including AF_NETLINK and AF_UNIX. Effectively, for AF_NETLINK this
           means that device configuration events received from systemd-
           udevd.service(8) are not delivered to the unit's processes. And for
           AF_UNIX this has the effect that AF_UNIX sockets in the abstract
           socket namespace of the host will become unavailable to the unit's
           processes (however, those located in the file system will continue to
           be accessible).

           Note that the implementation of this setting might be impossible (for
           example if network namespaces are not available), and the unit should
           be written in a way that does not solely rely on this setting for
           security.

           When this option is used on a socket unit any sockets bound on behalf
           of this unit will be bound within a private network namespace. This
           may be combined with JoinsNamespaceOf= to listen on sockets inside of
           network namespaces of other services.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       NetworkNamespacePath=
           Takes an absolute file system path refererring to a Linux network
           namespace pseudo-file (i.e. a file like /proc/$PID/ns/net or a bind
           mount or symlink to one). When set the invoked processes are added to
           the network namespace referenced by that path. The path has to point
           to a valid namespace file at the moment the processes are forked off.
           If this option is used PrivateNetwork= has no effect. If this option
           is used together with JoinsNamespaceOf= then it only has an effect if
           this unit is started before any of the listed units that have
           PrivateNetwork= or NetworkNamespacePath= configured, as otherwise the
           network namespace of those units is reused.

           When this option is used on a socket unit any sockets bound on behalf
           of this unit will be bound within the specified network namespace.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       PrivateUsers=
           Takes a boolean argument. If true, sets up a new user namespace for
           the executed processes and configures a minimal user and group
           mapping, that maps the "root" user and group as well as the unit's
           own user and group to themselves and everything else to the "nobody"
           user and group. This is useful to securely detach the user and group
           databases used by the unit from the rest of the system, and thus to
           create an effective sandbox environment. All files, directories,
           processes, IPC objects and other resources owned by users/groups not
           equaling "root" or the unit's own will stay visible from within the
           unit but appear owned by the "nobody" user and group. If this mode is
           enabled, all unit processes are run without privileges in the host
           user namespace (regardless if the unit's own user/group is "root" or
           not). Specifically this means that the process will have zero process
           capabilities on the host's user namespace, but full capabilities
           within the service's user namespace. Settings such as
           CapabilityBoundingSet= will affect only the latter, and there's no
           way to acquire additional capabilities in the host's user namespace.
           Defaults to off.

           When this setting is set up by a per-user instance of the service
           manager, the mapping of the "root" user and group to itself is
           omitted (unless the user manager is root). Additionally, in the
           per-user instance manager case, the user namespace will be set up
           before most other namespaces. This means that combining
           PrivateUsers=true with other namespaces will enable use of features
           not normally supported by the per-user instances of the service
           manager.

           This setting is particularly useful in conjunction with
           RootDirectory=/RootImage=, as the need to synchronize the user and
           group databases in the root directory and on the host is reduced, as
           the only users and groups who need to be matched are "root", "nobody"
           and the unit's own user and group.

           Note that the implementation of this setting might be impossible (for
           example if user namespaces are not available), and the unit should be
           written in a way that does not solely rely on this setting for
           security.

       ProtectHostname=
           Takes a boolean argument. When set, sets up a new UTS namespace for
           the executed processes. In addition, changing hostname or domainname
           is prevented. Defaults to off.

           Note that the implementation of this setting might be impossible (for
           example if UTS namespaces are not available), and the unit should be
           written in a way that does not solely rely on this setting for
           security.

           Note that when this option is enabled for a service hostname changes
           no longer propagate from the system into the service, it is hence not
           suitable for services that need to take notice of system hostname
           changes dynamically.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectClock=
           Takes a boolean argument. If set, writes to the hardware clock or
           system clock will be denied. It is recommended to turn this on for
           most services that do not need modify the clock. Defaults to off.
           Enabling this option removes CAP_SYS_TIME and CAP_WAKE_ALARM from the
           capability bounding set for this unit, installs a system call filter
           to block calls that can set the clock, and DeviceAllow=char-rtc r is
           implied. This ensures /dev/rtc0, /dev/rtc1, etc. are made read-only
           to the service. See systemd.resource-control(5) for the details about
           DeviceAllow=.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectKernelTunables=
           Takes a boolean argument. If true, kernel variables accessible
           through /proc/sys/, /sys/, /proc/sysrq-trigger, /proc/latency_stats,
           /proc/acpi, /proc/timer_stats, /proc/fs and /proc/irq will be made
           read-only to all processes of the unit. Usually, tunable kernel
           variables should be initialized only at boot-time, for example with
           the sysctl.d(5) mechanism. Few services need to write to these at
           runtime; it is hence recommended to turn this on for most services.
           For this setting the same restrictions regarding mount propagation
           and privileges apply as for ReadOnlyPaths= and related calls, see
           above. Defaults to off. If turned on and if running in user mode, or
           in system mode, but without the CAP_SYS_ADMIN capability (e.g.
           services for which User= is set), NoNewPrivileges=yes is implied.
           Note that this option does not prevent indirect changes to kernel
           tunables effected by IPC calls to other processes. However,
           InaccessiblePaths= may be used to make relevant IPC file system
           objects inaccessible. If ProtectKernelTunables= is set,
           MountAPIVFS=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectKernelModules=
           Takes a boolean argument. If true, explicit module loading will be
           denied. This allows module load and unload operations to be turned
           off on modular kernels. It is recommended to turn this on for most
           services that do not need special file systems or extra kernel
           modules to work. Defaults to off. Enabling this option removes
           CAP_SYS_MODULE from the capability bounding set for the unit, and
           installs a system call filter to block module system calls, also
           /usr/lib/modules is made inaccessible. For this setting the same
           restrictions regarding mount propagation and privileges apply as for
           ReadOnlyPaths= and related calls, see above. Note that limited
           automatic module loading due to user configuration or kernel mapping
           tables might still happen as side effect of requested user
           operations, both privileged and unprivileged. To disable module
           auto-load feature please see sysctl.d(5) kernel.modules_disabled
           mechanism and /proc/sys/kernel/modules_disabled documentation. If
           turned on and if running in user mode, or in system mode, but without
           the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectKernelLogs=
           Takes a boolean argument. If true, access to the kernel log ring
           buffer will be denied. It is recommended to turn this on for most
           services that do not need to read from or write to the kernel log
           ring buffer. Enabling this option removes CAP_SYSLOG from the
           capability bounding set for this unit, and installs a system call
           filter to block the syslog(2) system call (not to be confused with
           the libc API syslog(3) for userspace logging). The kernel exposes its
           log buffer to userspace via /dev/kmsg and /proc/kmsg. If enabled,
           these are made inaccessible to all the processes in the unit.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       ProtectControlGroups=
           Takes a boolean argument. If true, the Linux Control Groups
           (cgroups(7)) hierarchies accessible through /sys/fs/cgroup/ will be
           made read-only to all processes of the unit. Except for container
           managers no services should require write access to the control
           groups hierarchies; it is hence recommended to turn this on for most
           services. For this setting the same restrictions regarding mount
           propagation and privileges apply as for ReadOnlyPaths= and related
           calls, see above. Defaults to off. If ProtectControlGroups= is set,
           MountAPIVFS=yes is implied.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       RestrictAddressFamilies=
           Restricts the set of socket address families accessible to the
           processes of this unit. Takes a space-separated list of address
           family names to allow-list, such as AF_UNIX, AF_INET or AF_INET6.
           When prefixed with ~ the listed address families will be applied as
           deny list, otherwise as allow list. Note that this restricts access
           to the socket(2) system call only. Sockets passed into the process by
           other means (for example, by using socket activation with socket
           units, see systemd.socket(5)) are unaffected. Also, sockets created
           with socketpair() (which creates connected AF_UNIX sockets only) are
           unaffected. Note that this option has no effect on 32-bit x86, s390,
           s390x, mips, mips-le, ppc, ppc-le, ppc64, ppc64-le and is ignored
           (but works correctly on other ABIs, including x86-64). Note that on
           systems supporting multiple ABIs (such as x86/x86-64) it is
           recommended to turn off alternative ABIs for services, so that they
           cannot be used to circumvent the restrictions of this option.
           Specifically, it is recommended to combine this option with
           SystemCallArchitectures=native or similar. If running in user mode,
           or in system mode, but without the CAP_SYS_ADMIN capability (e.g.
           setting User=nobody), NoNewPrivileges=yes is implied. By default, no
           restrictions apply, all address families are accessible to processes.
           If assigned the empty string, any previous address family restriction
           changes are undone. This setting does not affect commands prefixed
           with "+".

           Use this option to limit exposure of processes to remote access, in
           particular via exotic and sensitive network protocols, such as
           AF_PACKET. Note that in most cases, the local AF_UNIX address family
           should be included in the configured allow list as it is frequently
           used for local communication, including for syslog(2) logging.

       RestrictNamespaces=
           Restricts access to Linux namespace functionality for the processes
           of this unit. For details about Linux namespaces, see namespaces(7).
           Either takes a boolean argument, or a space-separated list of
           namespace type identifiers. If false (the default), no restrictions
           on namespace creation and switching are made. If true, access to any
           kind of namespacing is prohibited. Otherwise, a space-separated list
           of namespace type identifiers must be specified, consisting of any
           combination of: cgroup, ipc, net, mnt, pid, user and uts. Any
           namespace type listed is made accessible to the unit's processes,
           access to namespace types not listed is prohibited (allow-listing).
           By prepending the list with a single tilde character ("~") the effect
           may be inverted: only the listed namespace types will be made
           inaccessible, all unlisted ones are permitted (deny-listing). If the
           empty string is assigned, the default namespace restrictions are
           applied, which is equivalent to false. This option may appear more
           than once, in which case the namespace types are merged by OR, or by
           AND if the lines are prefixed with "~" (see examples below).
           Internally, this setting limits access to the unshare(2), clone(2)
           and setns(2) system calls, taking the specified flags parameters into
           account. Note that — if this option is used — in addition to
           restricting creation and switching of the specified types of
           namespaces (or all of them, if true) access to the setns() system
           call with a zero flags parameter is prohibited. This setting is only
           supported on x86, x86-64, mips, mips-le, mips64, mips64-le,
           mips64-n32, mips64-le-n32, ppc64, ppc64-le, s390 and s390x, and
           enforces no restrictions on other architectures. If running in user
           mode, or in system mode, but without the CAP_SYS_ADMIN capability
           (e.g. setting User=), NoNewPrivileges=yes is implied.

           Example: if a unit has the following,

               RestrictNamespaces=cgroup ipc
               RestrictNamespaces=cgroup net

           then cgroup, ipc, and net are set. If the second line is prefixed
           with "~", e.g.,

               RestrictNamespaces=cgroup ipc
               RestrictNamespaces=~cgroup net

           then, only ipc is set.

       LockPersonality=
           Takes a boolean argument. If set, locks down the personality(2)
           system call so that the kernel execution domain may not be changed
           from the default or the personality selected with Personality=
           directive. This may be useful to improve security, because odd
           personality emulations may be poorly tested and source of
           vulnerabilities. If running in user mode, or in system mode, but
           without the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied.

       MemoryDenyWriteExecute=
           Takes a boolean argument. If set, attempts to create memory mappings
           that are writable and executable at the same time, or to change
           existing memory mappings to become executable, or mapping shared
           memory segments as executable are prohibited. Specifically, a system
           call filter is added that rejects mmap(2) system calls with both
           PROT_EXEC and PROT_WRITE set, mprotect(2) or pkey_mprotect(2) system
           calls with PROT_EXEC set and shmat(2) system calls with SHM_EXEC set.
           Note that this option is incompatible with programs and libraries
           that generate program code dynamically at runtime, including JIT
           execution engines, executable stacks, and code "trampoline" feature
           of various C compilers. This option improves service security, as it
           makes harder for software exploits to change running code
           dynamically. However, the protection can be circumvented, if the
           service can write to a filesystem, which is not mounted with noexec
           (such as /dev/shm), or it can use memfd_create(). This can be
           prevented by making such file systems inaccessible to the service
           (e.g.  InaccessiblePaths=/dev/shm) and installing further system call
           filters (SystemCallFilter=~memfd_create). Note that this feature is
           fully available on x86-64, and partially on x86. Specifically, the
           shmat() protection is not available on x86. Note that on systems
           supporting multiple ABIs (such as x86/x86-64) it is recommended to
           turn off alternative ABIs for services, so that they cannot be used
           to circumvent the restrictions of this option. Specifically, it is
           recommended to combine this option with
           SystemCallArchitectures=native or similar. If running in user mode,
           or in system mode, but without the CAP_SYS_ADMIN capability (e.g.
           setting User=), NoNewPrivileges=yes is implied.

       RestrictRealtime=
           Takes a boolean argument. If set, any attempts to enable realtime
           scheduling in a process of the unit are refused. This restricts
           access to realtime task scheduling policies such as SCHED_FIFO,
           SCHED_RR or SCHED_DEADLINE. See sched(7) for details about these
           scheduling policies. If running in user mode, or in system mode, but
           without the CAP_SYS_ADMIN capability (e.g. setting User=),
           NoNewPrivileges=yes is implied. Realtime scheduling policies may be
           used to monopolize CPU time for longer periods of time, and may hence
           be used to lock up or otherwise trigger Denial-of-Service situations
           on the system. It is hence recommended to restrict access to realtime
           scheduling to the few programs that actually require them. Defaults
           to off.

       RestrictSUIDSGID=
           Takes a boolean argument. If set, any attempts to set the set-user-ID
           (SUID) or set-group-ID (SGID) bits on files or directories will be
           denied (for details on these bits see inode(7)). If running in user
           mode, or in system mode, but without the CAP_SYS_ADMIN capability
           (e.g. setting User=), NoNewPrivileges=yes is implied. As the
           SUID/SGID bits are mechanisms to elevate privileges, and allows users
           to acquire the identity of other users, it is recommended to restrict
           creation of SUID/SGID files to the few programs that actually require
           them. Note that this restricts marking of any type of file system
           object with these bits, including both regular files and directories
           (where the SGID is a different meaning than for files, see
           documentation). This option is implied if DynamicUser= is enabled.
           Defaults to off.

       RemoveIPC=
           Takes a boolean parameter. If set, all System V and POSIX IPC objects
           owned by the user and group the processes of this unit are run as are
           removed when the unit is stopped. This setting only has an effect if
           at least one of User=, Group= and DynamicUser= are used. It has no
           effect on IPC objects owned by the root user. Specifically, this
           removes System V semaphores, as well as System V and POSIX shared
           memory segments and message queues. If multiple units use the same
           user or group the IPC objects are removed when the last of these
           units is stopped. This setting is implied if DynamicUser= is set.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       PrivateMounts=
           Takes a boolean parameter. If set, the processes of this unit will be
           run in their own private file system (mount) namespace with all mount
           propagation from the processes towards the host's main file system
           namespace turned off. This means any file system mount points
           established or removed by the unit's processes will be private to
           them and not be visible to the host. However, file system mount
           points established or removed on the host will be propagated to the
           unit's processes. See mount_namespaces(7) for details on file system
           namespaces. Defaults to off.

           When turned on, this executes three operations for each invoked
           process: a new CLONE_NEWNS namespace is created, after which all
           existing mounts are remounted to MS_SLAVE to disable propagation from
           the unit's processes to the host (but leaving propagation in the
           opposite direction in effect). Finally, the mounts are remounted
           again to the propagation mode configured with MountFlags=, see below.

           File system namespaces are set up individually for each process
           forked off by the service manager. Mounts established in the
           namespace of the process created by ExecStartPre= will hence be
           cleaned up automatically as soon as that process exits and will not
           be available to subsequent processes forked off for ExecStart= (and
           similar applies to the various other commands configured for units).
           Similarly, JoinsNamespaceOf= does not permit sharing kernel mount
           namespaces between units, it only enables sharing of the /tmp/ and
           /var/tmp/ directories.

           Other file system namespace unit settings — PrivateMounts=,
           PrivateTmp=, PrivateDevices=, ProtectSystem=, ProtectHome=,
           ReadOnlyPaths=, InaccessiblePaths=, ReadWritePaths=, ... — also
           enable file system namespacing in a fashion equivalent to this
           option. Hence it is primarily useful to explicitly request this
           behaviour if none of the other settings are used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       MountFlags=
           Takes a mount propagation setting: shared, slave or private, which
           controls whether file system mount points in the file system
           namespaces set up for this unit's processes will receive or propagate
           mounts and unmounts from other file system namespaces. See mount(2)
           for details on mount propagation, and the three propagation flags in
           particular.

           This setting only controls the final propagation setting in effect on
           all mount points of the file system namespace created for each
           process of this unit. Other file system namespacing unit settings
           (see the discussion in PrivateMounts= above) will implicitly disable
           mount and unmount propagation from the unit's processes towards the
           host by changing the propagation setting of all mount points in the
           unit's file system namespace to slave first. Setting this option to
           shared does not reestablish propagation in that case.

           If not set – but file system namespaces are enabled through another
           file system namespace unit setting – shared mount propagation is
           used, but — as mentioned — as slave is applied first, propagation
           from the unit's processes to the host is still turned off.

           It is not recommended to use private mount propagation for units, as
           this means temporary mounts (such as removable media) of the host
           will stay mounted and thus indefinitely busy in forked off processes,
           as unmount propagation events won't be received by the file system
           namespace of the unit.

           Usually, it is best to leave this setting unmodified, and use higher
           level file system namespacing options instead, in particular
           PrivateMounts=, see above.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

SYSTEM CALL FILTERING
       SystemCallFilter=
           Takes a space-separated list of system call names. If this setting is
           used, all system calls executed by the unit processes except for the
           listed ones will result in immediate process termination with the
           SIGSYS signal (allow-listing). (See SystemCallErrorNumber= below for
           changing the default action). If the first character of the list is
           "~", the effect is inverted: only the listed system calls will result
           in immediate process termination (deny-listing). Deny-listed system
           calls and system call groups may optionally be suffixed with a colon
           (":") and "errno" error number (between 0 and 4095) or errno name
           such as EPERM, EACCES or EUCLEAN (see errno(3) for a full list). This
           value will be returned when a deny-listed system call is triggered,
           instead of terminating the processes immediately. Special setting
           "kill" can be used to explicitly specify killing. This value takes
           precedence over the one given in SystemCallErrorNumber=, see below.
           If running in user mode, or in system mode, but without the
           CAP_SYS_ADMIN capability (e.g. setting User=nobody),
           NoNewPrivileges=yes is implied. This feature makes use of the Secure
           Computing Mode 2 interfaces of the kernel ('seccomp filtering') and
           is useful for enforcing a minimal sandboxing environment. Note that
           the execve(), exit(), exit_group(), getrlimit(), rt_sigreturn(),
           sigreturn() system calls and the system calls for querying time and
           sleeping are implicitly allow-listed and do not need to be listed
           explicitly. This option may be specified more than once, in which
           case the filter masks are merged. If the empty string is assigned,
           the filter is reset, all prior assignments will have no effect. This
           does not affect commands prefixed with "+".

           Note that on systems supporting multiple ABIs (such as x86/x86-64) it
           is recommended to turn off alternative ABIs for services, so that
           they cannot be used to circumvent the restrictions of this option.
           Specifically, it is recommended to combine this option with
           SystemCallArchitectures=native or similar.

           Note that strict system call filters may impact execution and error
           handling code paths of the service invocation. Specifically, access
           to the execve() system call is required for the execution of the
           service binary — if it is blocked service invocation will necessarily
           fail. Also, if execution of the service binary fails for some reason
           (for example: missing service executable), the error handling logic
           might require access to an additional set of system calls in order to
           process and log this failure correctly. It might be necessary to
           temporarily disable system call filters in order to simplify
           debugging of such failures.

           If you specify both types of this option (i.e. allow-listing and
           deny-listing), the first encountered will take precedence and will
           dictate the default action (termination or approval of a system
           call). Then the next occurrences of this option will add or delete
           the listed system calls from the set of the filtered system calls,
           depending of its type and the default action. (For example, if you
           have started with an allow list rule for read() and write(), and
           right after it add a deny list rule for write(), then write() will be
           removed from the set.)

           As the number of possible system calls is large, predefined sets of
           system calls are provided. A set starts with "@" character, followed
           by name of the set.

           Table 4. Currently predefined system call sets
           ┌────────────────┬─────────────────────────────┐
           │Set             Description                 │
           ├────────────────┼─────────────────────────────┤
           │@aio            │ Asynchronous I/O            │
           │                │ (io_setup(2), io_submit(2), │
           │                │ and related calls)          │
           ├────────────────┼─────────────────────────────┤
           │@basic-io       │ System calls for basic I/O: │
           │                │ reading, writing, seeking,  │
           │                │ file descriptor duplication │
           │                │ and closing (read(2),       │
           │                │ write(2), and related       │
           │                │ calls)                      │
           ├────────────────┼─────────────────────────────┤
           │@chown          │ Changing file ownership     │
           │                │ (chown(2), fchownat(2), and │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@clock          │ System calls for changing   │
           │                │ the system clock            │
           │                │ (adjtimex(2),               │
           │                │ settimeofday(2), and        │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@cpu-emulation  │ System calls for CPU        │
           │                │ emulation functionality     │
           │                │ (vm86(2) and related calls) │
           ├────────────────┼─────────────────────────────┤
           │@debug          │ Debugging, performance      │
           │                │ monitoring and tracing      │
           │                │ functionality (ptrace(2),   │
           │                │ perf_event_open(2) and      │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@file-system    │ File system operations:     │
           │                │ opening, creating files and │
           │                │ directories for read and    │
           │                │ write, renaming and         │
           │                │ removing them, reading file │
           │                │ properties, or creating     │
           │                │ hard and symbolic links     │
           ├────────────────┼─────────────────────────────┤
           │@io-event       │ Event loop system calls     │
           │                │ (poll(2), select(2),        │
           │                │ epoll(7), eventfd(2) and    │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@ipc            │ Pipes, SysV IPC, POSIX      │
           │                │ Message Queues and other    │
           │                │ IPC (mq_overview(7),        │
           │                │ svipc(7))                   │
           ├────────────────┼─────────────────────────────┤
           │@keyring        │ Kernel keyring access       │
           │                │ (keyctl(2) and related      │
           │                │ calls)                      │
           ├────────────────┼─────────────────────────────┤
           │@memlock        │ Locking of memory in RAM    │
           │                │ (mlock(2), mlockall(2) and  │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@module         │ Loading and unloading of    │
           │                │ kernel modules              │
           │                │ (init_module(2),            │
           │                │ delete_module(2) and        │
           │                │ related calls)              │
           ├────────────────┼─────────────────────────────┤
           │@mount          │ Mounting and unmounting of  │
           │                │ file systems (mount(2),     │
           │                │ chroot(2), and related      │
           │                │ calls)                      │
           ├────────────────┼─────────────────────────────┤
           │@network-io     │ Socket I/O (including local │
           │                │ AF_UNIX): socket(7),        │
           │                │ unix(7)                     │
           ├────────────────┼─────────────────────────────┤
           │@obsolete       │ Unusual, obsolete or        │
           │                │ unimplemented               │
           │                │ (create_module(2), gtty(2), │
           │                │ ...)                        │
           ├────────────────┼─────────────────────────────┤
           │@privileged     │ All system calls which need │
           │                │ super-user capabilities     │
           │                │ (capabilities(7))           │
           ├────────────────┼─────────────────────────────┤
           │@process        │ Process control, execution, │
           │                │ namespacing operations      │
           │                │ (clone(2), kill(2),         │
           │                │ namespaces(7), ...)         │
           ├────────────────┼─────────────────────────────┤
           │@raw-io         │ Raw I/O port access         │
           │                │ (ioperm(2), iopl(2),        │
           │                │ pciconfig_read(), ...)      │
           ├────────────────┼─────────────────────────────┤
           │@reboot         │ System calls for rebooting  │
           │                │ and reboot preparation      │
           │                │ (reboot(2), kexec(), ...)   │
           ├────────────────┼─────────────────────────────┤
           │@resources      │ System calls for changing   │
           │                │ resource limits, memory and │
           │                │ scheduling parameters       │
           │                │ (setrlimit(2),              │
           │                │ setpriority(2), ...)        │
           ├────────────────┼─────────────────────────────┤
           │@setuid         │ System calls for changing   │
           │                │ user ID and group ID        │
           │                │ credentials, (setuid(2),    │
           │                │ setgid(2), setresuid(2),    │
           │                │ ...)                        │
           ├────────────────┼─────────────────────────────┤
           │@signal         │ System calls for            │
           │                │ manipulating and handling   │
           │                │ process signals (signal(2), │
           │                │ sigprocmask(2), ...)        │
           ├────────────────┼─────────────────────────────┤
           │@swap           │ System calls for            │
           │                │ enabling/disabling swap     │
           │                │ devices (swapon(2),         │
           │                │ swapoff(2))                 │
           ├────────────────┼─────────────────────────────┤
           │@sync           │ Synchronizing files and     │
           │                │ memory to disk (fsync(2),   │
           │                │ msync(2), and related       │
           │                │ calls)                      │
           ├────────────────┼─────────────────────────────┤
           │@system-service │ A reasonable set of system  │
           │                │ calls used by common system │
           │                │ services, excluding any     │
           │                │ special purpose calls. This │
           │                │ is the recommended starting │
           │                │ point for allow-listing     │
           │                │ system calls for system     │
           │                │ services, as it contains    │
           │                │ what is typically needed by │
           │                │ system services, but        │
           │                │ excludes overly specific    │
           │                │ interfaces. For example,    │
           │                │ the following APIs are      │
           │                │ excluded: "@clock",         │
           │                │ "@mount", "@swap",          │
           │                │ "@reboot".                  │
           ├────────────────┼─────────────────────────────┤
           │@timer          │ System calls for scheduling │
           │                │ operations by time          │
           │                │ (alarm(2), timer_create(2), │
           │                │ ...)                        │
           ├────────────────┼─────────────────────────────┤
           │@known          │ All system calls defined by │
           │                │ the kernel. This list is    │
           │                │ defined statically in       │
           │                │ systemd based on a kernel   │
           │                │ version that was available  │
           │                │ when this systemd version   │
           │                │ was released. It will       │
           │                │ become progressively more   │
           │                │ out-of-date as the kernel   │
           │                │ is updated.                 │
           └────────────────┴─────────────────────────────┘
           Note, that as new system calls are added to the kernel, additional
           system calls might be added to the groups above. Contents of the sets
           may also change between systemd versions. In addition, the list of
           system calls depends on the kernel version and architecture for which
           systemd was compiled. Use systemd-analyze syscall-filter to list the
           actual list of system calls in each filter.

           Generally, allow-listing system calls (rather than deny-listing) is
           the safer mode of operation. It is recommended to enforce system call
           allow lists for all long-running system services. Specifically, the
           following lines are a relatively safe basic choice for the majority
           of system services:

               [Service]
               SystemCallFilter=@system-service
               SystemCallErrorNumber=EPERM

           Note that various kernel system calls are defined redundantly: there
           are multiple system calls for executing the same operation. For
           example, the pidfd_send_signal() system call may be used to execute
           operations similar to what can be done with the older kill() system
           call, hence blocking the latter without the former only provides weak
           protection. Since new system calls are added regularly to the kernel
           as development progresses, keeping system call deny lists
           comprehensive requires constant work. It is thus recommended to use
           allow-listing instead, which offers the benefit that new system calls
           are by default implicitly blocked until the allow list is updated.

           Also note that a number of system calls are required to be accessible
           for the dynamic linker to work. The dynamic linker is required for
           running most regular programs (specifically: all dynamic ELF
           binaries, which is how most distributions build packaged programs).
           This means that blocking these system calls (which include open(),
           openat() or mmap()) will make most programs typically shipped with
           generic distributions unusable.

           It is recommended to combine the file system namespacing related
           options with SystemCallFilter=~@mount, in order to prohibit the
           unit's processes to undo the mappings. Specifically these are the
           options PrivateTmp=, PrivateDevices=, ProtectSystem=, ProtectHome=,
           ProtectKernelTunables=, ProtectControlGroups=, ProtectKernelLogs=,
           ProtectClock=, ReadOnlyPaths=, InaccessiblePaths= and
           ReadWritePaths=.

       SystemCallErrorNumber=
           Takes an "errno" error number (between 1 and 4095) or errno name such
           as EPERM, EACCES or EUCLEAN, to return when the system call filter
           configured with SystemCallFilter= is triggered, instead of
           terminating the process immediately. See errno(3) for a full list of
           error codes. When this setting is not used, or when the empty string
           or the special setting "kill" is assigned, the process will be
           terminated immediately when the filter is triggered.

       SystemCallArchitectures=
           Takes a space-separated list of architecture identifiers to include
           in the system call filter. The known architecture identifiers are the
           same as for ConditionArchitecture= described in systemd.unit(5), as
           well as x32, mips64-n32, mips64-le-n32, and the special identifier
           native. The special identifier native implicitly maps to the native
           architecture of the system (or more precisely: to the architecture
           the system manager is compiled for). If running in user mode, or in
           system mode, but without the CAP_SYS_ADMIN capability (e.g. setting
           User=nobody), NoNewPrivileges=yes is implied. By default, this option
           is set to the empty list, i.e. no filtering is applied.

           If this setting is used, processes of this unit will only be
           permitted to call native system calls, and system calls of the
           specified architectures. For the purposes of this option, the x32
           architecture is treated as including x86-64 system calls. However,
           this setting still fulfills its purpose, as explained below, on x32.

           System call filtering is not equally effective on all architectures.
           For example, on x86 filtering of network socket-related calls is not
           possible, due to ABI limitations — a limitation that x86-64 does not
           have, however. On systems supporting multiple ABIs at the same time —
           such as x86/x86-64 — it is hence recommended to limit the set of
           permitted system call architectures so that secondary ABIs may not be
           used to circumvent the restrictions applied to the native ABI of the
           system. In particular, setting SystemCallArchitectures=native is a
           good choice for disabling non-native ABIs.

           System call architectures may also be restricted system-wide via the
           SystemCallArchitectures= option in the global configuration. See
           systemd-system.conf(5) for details.

       SystemCallLog=
           Takes a space-separated list of system call names. If this setting is
           used, all system calls executed by the unit processes for the listed
           ones will be logged. If the first character of the list is "~", the
           effect is inverted: all system calls except the listed system calls
           will be logged. If running in user mode, or in system mode, but
           without the CAP_SYS_ADMIN capability (e.g. setting User=nobody),
           NoNewPrivileges=yes is implied. This feature makes use of the Secure
           Computing Mode 2 interfaces of the kernel ('seccomp filtering') and
           is useful for auditing or setting up a minimal sandboxing
           environment. This option may be specified more than once, in which
           case the filter masks are merged. If the empty string is assigned,
           the filter is reset, all prior assignments will have no effect. This
           does not affect commands prefixed with "+".

ENVIRONMENT
       Environment=
           Sets environment variables for executed processes. Takes a
           space-separated list of variable assignments. This option may be
           specified more than once, in which case all listed variables will be
           set. If the same variable is set twice, the later setting will
           override the earlier setting. If the empty string is assigned to this
           option, the list of environment variables is reset, all prior
           assignments have no effect. Variable expansion is not performed
           inside the strings, however, specifier expansion is possible. The "$"
           character has no special meaning. If you need to assign a value
           containing spaces or the equals sign to a variable, use double quotes
           (") for the assignment.

           The names of the variables can contain ASCII letters, digits, and the
           underscore character. Variable names cannot be empty or start with a
           digit. In variable values, most characters are allowed, but
           non-printable characters are currently rejected.

           Example:

               Environment="VAR1=word1 word2" VAR2=word3 "VAR3=$word 5 6"

           gives three variables "VAR1", "VAR2", "VAR3" with the values "word1
           word2", "word3", "$word 5 6".

           See environ(7) for details about environment variables.

           Note that environment variables are not suitable for passing secrets
           (such as passwords, key material, ...) to service processes.
           Environment variables set for a unit are exposed to unprivileged
           clients via D-Bus IPC, and generally not understood as being data
           that requires protection. Moreover, environment variables are
           propagated down the process tree, including across security
           boundaries (such as setuid/setgid executables), and hence might leak
           to processes that should not have access to the secret data. Use
           LoadCredential= (see below) to pass data to unit processes securely.

       EnvironmentFile=
           Similar to Environment= but reads the environment variables from a
           text file. The text file should contain new-line-separated variable
           assignments. Empty lines, lines without an "=" separator, or lines
           starting with ; or # will be ignored, which may be used for
           commenting. A line ending with a backslash will be concatenated with
           the following one, allowing multiline variable definitions. The
           parser strips leading and trailing whitespace from the values of
           assignments, unless you use double quotes (").

           C escapes[7] are supported, but not most control characters[8].  "\t"
           and "\n" can be used to insert tabs and newlines within
           EnvironmentFile=.

           The argument passed should be an absolute filename or wildcard
           expression, optionally prefixed with "-", which indicates that if the
           file does not exist, it will not be read and no error or warning
           message is logged. This option may be specified more than once in
           which case all specified files are read. If the empty string is
           assigned to this option, the list of file to read is reset, all prior
           assignments have no effect.

           The files listed with this directive will be read shortly before the
           process is executed (more specifically, after all processes from a
           previous unit state terminated. This means you can generate these
           files in one unit state, and read it with this option in the next.
           The files are read from the file system of the service manager,
           before any file system changes like bind mounts take place).

           Settings from these files override settings made with Environment=.
           If the same variable is set twice from these files, the files will be
           read in the order they are specified and the later setting will
           override the earlier setting.

       PassEnvironment=
           Pass environment variables set for the system service manager to
           executed processes. Takes a space-separated list of variable names.
           This option may be specified more than once, in which case all listed
           variables will be passed. If the empty string is assigned to this
           option, the list of environment variables to pass is reset, all prior
           assignments have no effect. Variables specified that are not set for
           the system manager will not be passed and will be silently ignored.
           Note that this option is only relevant for the system service
           manager, as system services by default do not automatically inherit
           any environment variables set for the service manager itself.
           However, in case of the user service manager all environment
           variables are passed to the executed processes anyway, hence this
           option is without effect for the user service manager.

           Variables set for invoked processes due to this setting are subject
           to being overridden by those configured with Environment= or
           EnvironmentFile=.

           C escapes[7] are supported, but not most control characters[8].  "\t"
           and "\n" can be used to insert tabs and newlines within
           EnvironmentFile=.

           Example:

               PassEnvironment=VAR1 VAR2 VAR3

           passes three variables "VAR1", "VAR2", "VAR3" with the values set for
           those variables in PID1.

           See environ(7) for details about environment variables.

       UnsetEnvironment=
           Explicitly unset environment variable assignments that would normally
           be passed from the service manager to invoked processes of this unit.
           Takes a space-separated list of variable names or variable
           assignments. This option may be specified more than once, in which
           case all listed variables/assignments will be unset. If the empty
           string is assigned to this option, the list of environment
           variables/assignments to unset is reset. If a variable assignment is
           specified (that is: a variable name, followed by "=", followed by its
           value), then any environment variable matching this precise
           assignment is removed. If a variable name is specified (that is a
           variable name without any following "=" or value), then any
           assignment matching the variable name, regardless of its value is
           removed. Note that the effect of UnsetEnvironment= is applied as
           final step when the environment list passed to executed processes is
           compiled. That means it may undo assignments from any configuration
           source, including assignments made through Environment= or
           EnvironmentFile=, inherited from the system manager's global set of
           environment variables, inherited via PassEnvironment=, set by the
           service manager itself (such as $NOTIFY_SOCKET and such), or set by a
           PAM module (in case PAMName= is used).

           See "Environment Variables in Spawned Processes" below for a
           description of how those settings combine to form the inherited
           environment. See environ(7) for general information about environment
           variables.

LOGGING AND STANDARD INPUT/OUTPUT
       StandardInput=
           Controls where file descriptor 0 (STDIN) of the executed processes is
           connected to. Takes one of null, tty, tty-force, tty-fail, data,
           file:path, socket or fd:name.

           If null is selected, standard input will be connected to /dev/null,
           i.e. all read attempts by the process will result in immediate EOF.

           If tty is selected, standard input is connected to a TTY (as
           configured by TTYPath=, see below) and the executed process becomes
           the controlling process of the terminal. If the terminal is already
           being controlled by another process, the executed process waits until
           the current controlling process releases the terminal.

           tty-force is similar to tty, but the executed process is forcefully
           and immediately made the controlling process of the terminal,
           potentially removing previous controlling processes from the
           terminal.

           tty-fail is similar to tty, but if the terminal already has a
           controlling process start-up of the executed process fails.

           The data option may be used to configure arbitrary textual or binary
           data to pass via standard input to the executed process. The data to
           pass is configured via StandardInputText=/StandardInputData= (see
           below). Note that the actual file descriptor type passed (memory
           file, regular file, UNIX pipe, ...) might depend on the kernel and
           available privileges. In any case, the file descriptor is read-only,
           and when read returns the specified data followed by EOF.

           The file:path option may be used to connect a specific file system
           object to standard input. An absolute path following the ":"
           character is expected, which may refer to a regular file, a FIFO or
           special file. If an AF_UNIX socket in the file system is specified, a
           stream socket is connected to it. The latter is useful for connecting
           standard input of processes to arbitrary system services.

           The socket option is valid in socket-activated services only, and
           requires the relevant socket unit file (see systemd.socket(5) for
           details) to have Accept=yes set, or to specify a single socket only.
           If this option is set, standard input will be connected to the socket
           the service was activated from, which is primarily useful for
           compatibility with daemons designed for use with the traditional
           inetd(8) socket activation daemon.

           The fd:name option connects standard input to a specific, named file
           descriptor provided by a socket unit. The name may be specified as
           part of this option, following a ":" character (e.g.  "fd:foobar").
           If no name is specified, the name "stdin" is implied (i.e.  "fd" is
           equivalent to "fd:stdin"). At least one socket unit defining the
           specified name must be provided via the Sockets= option, and the file
           descriptor name may differ from the name of its containing socket
           unit. If multiple matches are found, the first one will be used. See
           FileDescriptorName= in systemd.socket(5) for more details about named
           file descriptors and their ordering.

           This setting defaults to null, unless
           StandardInputText=/StandardInputData= are set, in which case it
           defaults to data.

       StandardOutput=
           Controls where file descriptor 1 (stdout) of the executed processes
           is connected to. Takes one of inherit, null, tty, journal, kmsg,
           journal+console, kmsg+console, file:path, append:path, socket or
           fd:name.

           inherit duplicates the file descriptor of standard input for standard
           output.

           null connects standard output to /dev/null, i.e. everything written
           to it will be lost.

           tty connects standard output to a tty (as configured via TTYPath=,
           see below). If the TTY is used for output only, the executed process
           will not become the controlling process of the terminal, and will not
           fail or wait for other processes to release the terminal.

           journal connects standard output with the journal, which is
           accessible via journalctl(1). Note that everything that is written to
           kmsg (see below) is implicitly stored in the journal as well, the
           specific option listed below is hence a superset of this one. (Also
           note that any external, additional syslog daemons receive their log
           data from the journal, too, hence this is the option to use when
           logging shall be processed with such a daemon.)

           kmsg connects standard output with the kernel log buffer which is
           accessible via dmesg(1), in addition to the journal. The journal
           daemon might be configured to send all logs to kmsg anyway, in which
           case this option is no different from journal.

           journal+console and kmsg+console work in a similar way as the two
           options above but copy the output to the system console as well.

           The file:path option may be used to connect a specific file system
           object to standard output. The semantics are similar to the same
           option of StandardInput=, see above. If path refers to a regular file
           on the filesystem, it is opened (created if it doesn't exist yet) for
           writing at the beginning of the file, but without truncating it. If
           standard input and output are directed to the same file path, it is
           opened only once, for reading as well as writing and duplicated. This
           is particularly useful when the specified path refers to an AF_UNIX
           socket in the file system, as in that case only a single stream
           connection is created for both input and output.

           append:path is similar to file:path above, but it opens the file in
           append mode.

           socket connects standard output to a socket acquired via socket
           activation. The semantics are similar to the same option of
           StandardInput=, see above.

           The fd:name option connects standard output to a specific, named file
           descriptor provided by a socket unit. A name may be specified as part
           of this option, following a ":" character (e.g.  "fd:foobar"). If no
           name is specified, the name "stdout" is implied (i.e.  "fd" is
           equivalent to "fd:stdout"). At least one socket unit defining the
           specified name must be provided via the Sockets= option, and the file
           descriptor name may differ from the name of its containing socket
           unit. If multiple matches are found, the first one will be used. See
           FileDescriptorName= in systemd.socket(5) for more details about named
           descriptors and their ordering.

           If the standard output (or error output, see below) of a unit is
           connected to the journal or the kernel log buffer, the unit will
           implicitly gain a dependency of type After= on
           systemd-journald.socket (also see the "Implicit Dependencies" section
           above). Also note that in this case stdout (or stderr, see below)
           will be an AF_UNIX stream socket, and not a pipe or FIFO that can be
           re-opened. This means when executing shell scripts the construct echo
           "hello" > /dev/stderr for writing text to stderr will not work. To
           mitigate this use the construct echo "hello" >&2 instead, which is
           mostly equivalent and avoids this pitfall.

           This setting defaults to the value set with DefaultStandardOutput= in
           systemd-system.conf(5), which defaults to journal. Note that setting
           this parameter might result in additional dependencies to be added to
           the unit (see above).

       StandardError=
           Controls where file descriptor 2 (stderr) of the executed processes
           is connected to. The available options are identical to those of
           StandardOutput=, with some exceptions: if set to inherit the file
           descriptor used for standard output is duplicated for standard error,
           while fd:name will use a default file descriptor name of "stderr".

           This setting defaults to the value set with DefaultStandardError= in
           systemd-system.conf(5), which defaults to inherit. Note that setting
           this parameter might result in additional dependencies to be added to
           the unit (see above).

       StandardInputText=, StandardInputData=
           Configures arbitrary textual or binary data to pass via file
           descriptor 0 (STDIN) to the executed processes. These settings have
           no effect unless StandardInput= is set to data (which is the default
           if StandardInput= is not set otherwise, but
           StandardInputText=/StandardInputData= is). Use this option to embed
           process input data directly in the unit file.

           StandardInputText= accepts arbitrary textual data. C-style escapes
           for special characters as well as the usual "%"-specifiers are
           resolved. Each time this setting is used the specified text is
           appended to the per-unit data buffer, followed by a newline character
           (thus every use appends a new line to the end of the buffer). Note
           that leading and trailing whitespace of lines configured with this
           option is removed. If an empty line is specified the buffer is
           cleared (hence, in order to insert an empty line, add an additional
           "\n" to the end or beginning of a line).

           StandardInputData= accepts arbitrary binary data, encoded in
           Base64[9]. No escape sequences or specifiers are resolved. Any
           whitespace in the encoded version is ignored during decoding.

           Note that StandardInputText= and StandardInputData= operate on the
           same data buffer, and may be mixed in order to configure both binary
           and textual data for the same input stream. The textual or binary
           data is joined strictly in the order the settings appear in the unit
           file. Assigning an empty string to either will reset the data buffer.

           Please keep in mind that in order to maintain readability long unit
           file settings may be split into multiple lines, by suffixing each
           line (except for the last) with a "\" character (see systemd.unit(5)
           for details). This is particularly useful for large data configured
           with these two options. Example:

               ...
               StandardInput=data
               StandardInputData=SWNrIHNpdHplIGRhIHVuJyBlc3NlIEtsb3BzLAp1ZmYgZWVtYWwga2xvcHAncy4KSWNrIGtpZWtl \
                                 LCBzdGF1bmUsIHd1bmRyZSBtaXIsCnVmZiBlZW1hbCBqZWh0IHNlIHVmZiBkaWUgVMO8ci4KTmFu \
                                 dSwgZGVuayBpY2ssIGljayBkZW5rIG5hbnUhCkpldHogaXNzZSB1ZmYsIGVyc2NodCB3YXIgc2Ug \
                                 enUhCkljayBqZWhlIHJhdXMgdW5kIGJsaWNrZSDigJQKdW5kIHdlciBzdGVodCBkcmF1w59lbj8g \
                                 SWNrZSEK
               ...

       LogLevelMax=
           Configures filtering by log level of log messages generated by this
           unit. Takes a syslog log level, one of emerg (lowest log level, only
           highest priority messages), alert, crit, err, warning, notice, info,
           debug (highest log level, also lowest priority messages). See
           syslog(3) for details. By default no filtering is applied (i.e. the
           default maximum log level is debug). Use this option to configure the
           logging system to drop log messages of a specific service above the
           specified level. For example, set LogLevelMax=info in order to turn
           off debug logging of a particularly chatty unit. Note that the
           configured level is applied to any log messages written by any of the
           processes belonging to this unit, sent via any supported logging
           protocol. The filtering is applied early in the logging pipeline,
           before any kind of further processing is done. Moreover, messages
           which pass through this filter successfully might still be dropped by
           filters applied at a later stage in the logging subsystem. For
           example, MaxLevelStore= configured in journald.conf(5) might prohibit
           messages of higher log levels to be stored on disk, even though the
           per-unit LogLevelMax= permitted it to be processed.

       LogExtraFields=
           Configures additional log metadata fields to include in all log
           records generated by processes associated with this unit. This
           setting takes one or more journal field assignments in the format
           "FIELD=VALUE" separated by whitespace. See systemd.journal-fields(7)
           for details on the journal field concept. Even though the underlying
           journal implementation permits binary field values, this setting
           accepts only valid UTF-8 values. To include space characters in a
           journal field value, enclose the assignment in double quotes (").
           The usual specifiers are expanded in all assignments (see below).
           Note that this setting is not only useful for attaching additional
           metadata to log records of a unit, but given that all fields and
           values are indexed may also be used to implement cross-unit log
           record matching. Assign an empty string to reset the list.

       LogRateLimitIntervalSec=, LogRateLimitBurst=
           Configures the rate limiting that is applied to messages generated by
           this unit. If, in the time interval defined by
           LogRateLimitIntervalSec=, more messages than specified in
           LogRateLimitBurst= are logged by a service, all further messages
           within the interval are dropped until the interval is over. A message
           about the number of dropped messages is generated. The time
           specification for LogRateLimitIntervalSec= may be specified in the
           following units: "s", "min", "h", "ms", "us" (see systemd.time(7) for
           details). The default settings are set by RateLimitIntervalSec= and
           RateLimitBurst= configured in journald.conf(5).

       LogNamespace=
           Run the unit's processes in the specified journal namespace. Expects
           a short user-defined string identifying the namespace. If not used
           the processes of the service are run in the default journal
           namespace, i.e. their log stream is collected and processed by
           systemd-journald.service. If this option is used any log data
           generated by processes of this unit (regardless if via the syslog(),
           journal native logging or stdout/stderr logging) is collected and
           processed by an instance of the systemd-journald@.service template
           unit, which manages the specified namespace. The log data is stored
           in a data store independent from the default log namespace's data
           store. See systemd-journald.service(8) for details about journal
           namespaces.

           Internally, journal namespaces are implemented through Linux mount
           namespacing and over-mounting the directory that contains the
           relevant AF_UNIX sockets used for logging in the unit's mount
           namespace. Since mount namespaces are used this setting disconnects
           propagation of mounts from the unit's processes to the host, similar
           to how ReadOnlyPaths= and similar settings (see above) work. Journal
           namespaces may hence not be used for services that need to establish
           mount points on the host.

           When this option is used the unit will automatically gain ordering
           and requirement dependencies on the two socket units associated with
           the systemd-journald@.service instance so that they are automatically
           established prior to the unit starting up. Note that when this option
           is used log output of this service does not appear in the regular
           journalctl(1) output, unless the --namespace= option is used.

           This option is only available for system services and is not
           supported for services running in per-user instances of the service
           manager.

       SyslogIdentifier=
           Sets the process name ("syslog tag") to prefix log lines sent to the
           logging system or the kernel log buffer with. If not set, defaults to
           the process name of the executed process. This option is only useful
           when StandardOutput= or StandardError= are set to journal or kmsg (or
           to the same settings in combination with +console) and only applies
           to log messages written to stdout or stderr.

       SyslogFacility=
           Sets the syslog facility identifier to use when logging. One of kern,
           user, mail, daemon, auth, syslog, lpr, news, uucp, cron, authpriv,
           ftp, local0, local1, local2, local3, local4, local5, local6 or
           local7. See syslog(3) for details. This option is only useful when
           StandardOutput= or StandardError= are set to journal or kmsg (or to
           the same settings in combination with +console), and only applies to
           log messages written to stdout or stderr. Defaults to daemon.

       SyslogLevel=
           The default syslog log level to use when logging to the logging
           system or the kernel log buffer. One of emerg, alert, crit, err,
           warning, notice, info, debug. See syslog(3) for details. This option
           is only useful when StandardOutput= or StandardError= are set to
           journal or kmsg (or to the same settings in combination with
           +console), and only applies to log messages written to stdout or
           stderr. Note that individual lines output by executed processes may
           be prefixed with a different log level which can be used to override
           the default log level specified here. The interpretation of these
           prefixes may be disabled with SyslogLevelPrefix=, see below. For
           details, see sd-daemon(3). Defaults to info.

       SyslogLevelPrefix=
           Takes a boolean argument. If true and StandardOutput= or
           StandardError= are set to journal or kmsg (or to the same settings in
           combination with +console), log lines written by the executed process
           that are prefixed with a log level will be processed with this log
           level set but the prefix removed. If set to false, the interpretation
           of these prefixes is disabled and the logged lines are passed on
           as-is. This only applies to log messages written to stdout or stderr.
           For details about this prefixing see sd-daemon(3). Defaults to true.

       TTYPath=
           Sets the terminal device node to use if standard input, output, or
           error are connected to a TTY (see above). Defaults to /dev/console.

       TTYReset=
           Reset the terminal device specified with TTYPath= before and after
           execution. Defaults to "no".

       TTYVHangup=
           Disconnect all clients which have opened the terminal device
           specified with TTYPath= before and after execution. Defaults to "no".

       TTYVTDisallocate=
           If the terminal device specified with TTYPath= is a virtual console
           terminal, try to deallocate the TTY before and after execution. This
           ensures that the screen and scrollback buffer is cleared. Defaults to
           "no".

CREDENTIALS
       LoadCredential=ID:PATH
           Pass a credential to the unit. Credentials are limited-size binary or
           textual objects that may be passed to unit processes. They are
           primarily used for passing cryptographic keys (both public and
           private) or certificates, user account information or identity
           information from host to services. The data is accessible from the
           unit's processes via the file system, at a read-only location that
           (if possible and permitted) is backed by non-swappable memory. The
           data is only accessible to the user associated with the unit, via the
           User=/DynamicUser= settings (as well as the superuser). When
           available, the location of credentials is exported as the
           $CREDENTIALS_DIRECTORY environment variable to the unit's processes.

           The LoadCredential= setting takes a textual ID to use as name for a
           credential plus a file system path. The ID must be a short ASCII
           string suitable as filename in the filesystem, and may be chosen
           freely by the user. If the specified path is absolute it is opened as
           regular file and the credential data is read from it. If the absolute
           path refers to an AF_UNIX stream socket in the file system a
           connection is made to it (only once at unit start-up) and the
           credential data read from the connection, providing an easy IPC
           integration point for dynamically providing credentials from other
           services. If the specified path is not absolute and itself qualifies
           as valid credential identifier it is understood to refer to a
           credential that the service manager itself received via the
           $CREDENTIALS_DIRECTORY environment variable, which may be used to
           propagate credentials from an invoking environment (e.g. a container
           manager that invoked the service manager) into a service. The
           contents of the file/socket may be arbitrary binary or textual data,
           including newline characters and NUL bytes. This option may be used
           multiple times, each time defining an additional credential to pass
           to the unit.

           The credential files/IPC sockets must be accessible to the service
           manager, but don't have to be directly accessible to the unit's
           processes: the credential data is read and copied into separate,
           read-only copies for the unit that are accessible to appropriately
           privileged processes. This is particularly useful in combination with
           DynamicUser= as this way privileged data can be made available to
           processes running under a dynamic UID (i.e. not a previously known
           one) without having to open up access to all users.

           In order to reference the path a credential may be read from within a
           ExecStart= command line use "${CREDENTIALS_DIRECTORY}/mycred", e.g.
           "ExecStart=cat ${CREDENTIALS_DIRECTORY}/mycred".

           Currently, an accumulated credential size limit of 1M bytes per unit
           is enforced.

           If referencing an AF_UNIX stream socket to connect to, the connection
           will originate from an abstract namespace socket, that includes
           information about the unit and the credential ID in its socket name.
           Use getpeername(2) to query this information. The returned socket
           name is formatted as NUL RANDOM "/unit/" UNIT "/" ID, i.e. a NUL byte
           (as required for abstract namespace socket names), followed by a
           random string (consisting of alphadecimal characters), followed by
           the literal string "/unit/", followed by the requesting unit name,
           followed by the literal character "/", followed by the textual
           credential ID requested. Example:
           "\0adf9d86b6eda275e/unit/foobar.service/credx" in case the credential
           "credx" is requested for a unit "foobar.service". This functionality
           is useful for using a single listening socket to serve credentials to
           multiple consumers.

       SetCredential=ID:VALUE
           The SetCredential= setting is similar to LoadCredential= but accepts
           a literal value to use as data for the credential, instead of a file
           system path to read the data from. Do not use this option for data
           that is supposed to be secret, as it is accessible to unprivileged
           processes via IPC. It's only safe to use this for user IDs, public
           key material and similar non-sensitive data. For everything else use
           LoadCredential=. In order to embed binary data into the credential
           data use C-style escaping (i.e.  "\n" to embed a newline, or "\x00"
           to embed a NUL byte).

           If a credential of the same ID is listed in both LoadCredential= and
           SetCredential=, the latter will act as default if the former cannot
           be retrieved. In this case not being able to retrieve the credential
           from the path specified in LoadCredential= is not considered fatal.

SYSTEM V COMPATIBILITY
       UtmpIdentifier=
           Takes a four character identifier string for an utmp(5) and wtmp
           entry for this service. This should only be set for services such as
           getty implementations (such as agetty(8)) where utmp/wtmp entries
           must be created and cleared before and after execution, or for
           services that shall be executed as if they were run by a getty
           process (see below). If the configured string is longer than four
           characters, it is truncated and the terminal four characters are
           used. This setting interprets %I style string replacements. This
           setting is unset by default, i.e. no utmp/wtmp entries are created or
           cleaned up for this service.

       UtmpMode=
           Takes one of "init", "login" or "user". If UtmpIdentifier= is set,
           controls which type of utmp(5)/wtmp entries for this service are
           generated. This setting has no effect unless UtmpIdentifier= is set
           too. If "init" is set, only an INIT_PROCESS entry is generated and
           the invoked process must implement a getty-compatible utmp/wtmp
           logic. If "login" is set, first an INIT_PROCESS entry, followed by a
           LOGIN_PROCESS entry is generated. In this case, the invoked process
           must implement a login(1)-compatible utmp/wtmp logic. If "user" is
           set, first an INIT_PROCESS entry, then a LOGIN_PROCESS entry and
           finally a USER_PROCESS entry is generated. In this case, the invoked
           process may be any process that is suitable to be run as session
           leader. Defaults to "init".

ENVIRONMENT VARIABLES IN SPAWNED PROCESSES
       Processes started by the service manager are executed with an environment
       variable block assembled from multiple sources. Processes started by the
       system service manager generally do not inherit environment variables set
       for the service manager itself (but this may be altered via
       PassEnvironment=), but processes started by the user service manager
       instances generally do inherit all environment variables set for the
       service manager itself.

       For each invoked process the list of environment variables set is
       compiled from the following sources:

       •   Variables globally configured for the service manager, using the
           DefaultEnvironment= setting in systemd-system.conf(5), the kernel
           command line option systemd.setenv= understood by systemd(1), or via
           systemctl(1) set-environment verb.

       •   Variables defined by the service manager itself (see the list below).

       •   Variables set in the service manager's own environment variable block
           (subject to PassEnvironment= for the system service manager).

       •   Variables set via Environment= in the unit file.

       •   Variables read from files specified via EnvironmentFile= in the unit
           file.

       •   Variables set by any PAM modules in case PAMName= is in effect,
           cf. pam_env(8).

       If the same environment variable is set by multiple of these sources, the
       later source — according to the order of the list above — wins. Note that
       as the final step all variables listed in UnsetEnvironment= are removed
       from the compiled environment variable list, immediately before it is
       passed to the executed process.

       The general philosophy is to expose a small curated list of environment
       variables to processes. Services started by the system manager (PID 1)
       will be started, without additional service-specific configuration, with
       just a few environment variables. The user manager inherits environment
       variables as any other system service, but in addition may receive
       additional environment variables from PAM, and, typically, additional
       imported variables when the user starts a graphical session. It is
       recommended to keep the environment blocks in both the system and user
       managers managers lean.

       Hint: systemd-run -P env and systemd-run --user -P env print the
       effective system and user service environment blocks.

   Environment Variables Set or Propagated by the Service Manager
       The following environment variables are propagated by the service manager
       or generated internally for each invoked process:

       $PATH
           Colon-separated list of directories to use when launching
           executables.  systemd uses a fixed value of
           "/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin" in the system
           manager. When compiled for systems with "unmerged /usr/" (/bin is not
           a symlink to /usr/bin), ":/sbin:/bin" is appended. In case of the the
           user manager, a different path may be configured by the distribution.
           It is recommended to not rely on the order of entries, and have only
           one program with a given name in $PATH.

       $LANG
           Locale. Can be set in locale.conf(5) or on the kernel command line
           (see systemd(1) and kernel-command-line(7)).

       $USER, $LOGNAME, $HOME, $SHELL
           User name (twice), home directory, and the login shell. The variables
           are set for the units that have User= set, which includes user
           systemd instances. See passwd(5).

       $INVOCATION_ID
           Contains a randomized, unique 128bit ID identifying each runtime
           cycle of the unit, formatted as 32 character hexadecimal string. A
           new ID is assigned each time the unit changes from an inactive state
           into an activating or active state, and may be used to identify this
           specific runtime cycle, in particular in data stored offline, such as
           the journal. The same ID is passed to all processes run as part of
           the unit.

       $XDG_RUNTIME_DIR
           The directory to use for runtime objects (such as IPC objects) and
           volatile state. Set for all services run by the user systemd
           instance, as well as any system services that use PAMName= with a PAM
           stack that includes pam_systemd. See below and pam_systemd(8) for
           more information.

       $RUNTIME_DIRECTORY, $STATE_DIRECTORY, $CACHE_DIRECTORY, $LOGS_DIRECTORY,
       $CONFIGURATION_DIRECTORY
           Absolute paths to the directories defined with RuntimeDirectory=,
           StateDirectory=, CacheDirectory=, LogsDirectory=, and
           ConfigurationDirectory= when those settings are used.

       $CREDENTIALS_DIRECTORY
           An absolute path to the per-unit directory with credentials
           configured via LoadCredential=/SetCredential=. The directory is
           marked read-only and is placed in unswappable memory (if supported
           and permitted), and is only accessible to the UID associated with the
           unit via User= or DynamicUser= (and the superuser).

       $MAINPID
           The PID of the unit's main process if it is known. This is only set
           for control processes as invoked by ExecReload= and similar.

       $MANAGERPID
           The PID of the user systemd instance, set for processes spawned by
           it.

       $LISTEN_FDS, $LISTEN_PID, $LISTEN_FDNAMES
           Information about file descriptors passed to a service for socket
           activation. See sd_listen_fds(3).

       $NOTIFY_SOCKET
           The socket sd_notify() talks to. See sd_notify(3).

       $WATCHDOG_PID, $WATCHDOG_USEC
           Information about watchdog keep-alive notifications. See
           sd_watchdog_enabled(3).

       $TERM
           Terminal type, set only for units connected to a terminal
           (StandardInput=tty, StandardOutput=tty, or StandardError=tty). See
           termcap(5).

       $LOG_NAMESPACE
           Contains the name of the selected logging namespace when the
           LogNamespace= service setting is used.

       $JOURNAL_STREAM
           If the standard output or standard error output of the executed
           processes are connected to the journal (for example, by setting
           StandardError=journal) $JOURNAL_STREAM contains the device and inode
           numbers of the connection file descriptor, formatted in decimal,
           separated by a colon (":"). This permits invoked processes to safely
           detect whether their standard output or standard error output are
           connected to the journal. The device and inode numbers of the file
           descriptors should be compared with the values set in the environment
           variable to determine whether the process output is still connected
           to the journal. Note that it is generally not sufficient to only
           check whether $JOURNAL_STREAM is set at all as services might invoke
           external processes replacing their standard output or standard error
           output, without unsetting the environment variable.

           If both standard output and standard error of the executed processes
           are connected to the journal via a stream socket, this environment
           variable will contain information about the standard error stream, as
           that's usually the preferred destination for log data. (Note that
           typically the same stream is used for both standard output and
           standard error, hence very likely the environment variable contains
           device and inode information matching both stream file descriptors.)

           This environment variable is primarily useful to allow services to
           optionally upgrade their used log protocol to the native journal
           protocol (using sd_journal_print(3) and other functions) if their
           standard output or standard error output is connected to the journal
           anyway, thus enabling delivery of structured metadata along with
           logged messages.

       $SERVICE_RESULT
           Only defined for the service unit type, this environment variable is
           passed to all ExecStop= and ExecStopPost= processes, and encodes the
           service "result". Currently, the following values are defined:

           Table 5. Defined $SERVICE_RESULT values
           ┌──────────────────┬─────────────────────────────┐
           │Value             Meaning                     │
           ├──────────────────┼─────────────────────────────┤
           │"success"         │ The service ran             │
           │                  │ successfully and exited     │
           │                  │ cleanly.                    │
           ├──────────────────┼─────────────────────────────┤
           │"protocol"        │ A protocol violation        │
           │                  │ occurred: the service did   │
           │                  │ not take the steps required │
           │                  │ by its unit configuration   │
           │                  │ (specifically what is       │
           │                  │ configured in its Type=     │
           │                  │ setting).                   │
           ├──────────────────┼─────────────────────────────┤
           │"timeout"         │ One of the steps timed out. │
           ├──────────────────┼─────────────────────────────┤
           │"exit-code"       │ Service process exited with │
           │                  │ a non-zero exit code; see   │
           │                  │ $EXIT_CODE below for the    │
           │                  │ actual exit code returned.  │
           ├──────────────────┼─────────────────────────────┤
           │"signal"          │ A service process was       │
           │                  │ terminated abnormally by a  │
           │                  │ signal, without dumping     │
           │                  │ core. See $EXIT_CODE below  │
           │                  │ for the actual signal       │
           │                  │ causing the termination.    │
           ├──────────────────┼─────────────────────────────┤
           │"core-dump"       │ A service process           │
           │                  │ terminated abnormally with  │
           │                  │ a signal and dumped core.   │
           │                  │ See $EXIT_CODE below for    │
           │                  │ the signal causing the      │
           │                  │ termination.                │
           ├──────────────────┼─────────────────────────────┤
           │"watchdog"        │ Watchdog keep-alive ping    │
           │                  │ was enabled for the         │
           │                  │ service, but the deadline   │
           │                  │ was missed.                 │
           ├──────────────────┼─────────────────────────────┤
           │"start-limit-hit" │ A start limit was defined   │
           │                  │ for the unit and it was     │
           │                  │ hit, causing the unit to    │
           │                  │ fail to start. See          │
           │                  │ systemd.unit(5)'s           │
           │                  │ StartLimitIntervalSec= and  │
           │                  │ StartLimitBurst= for        │
           │                  │ details.                    │
           ├──────────────────┼─────────────────────────────┤
           │"resources"       │ A catch-all condition in    │
           │                  │ case a system operation     │
           │                  │ failed.                     │
           └──────────────────┴─────────────────────────────┘
           This environment variable is useful to monitor failure or successful
           termination of a service. Even though this variable is available in
           both ExecStop= and ExecStopPost=, it is usually a better choice to
           place monitoring tools in the latter, as the former is only invoked
           for services that managed to start up correctly, and the latter
           covers both services that failed during their start-up and those
           which failed during their runtime.

       $EXIT_CODE, $EXIT_STATUS
           Only defined for the service unit type, these environment variables
           are passed to all ExecStop=, ExecStopPost= processes and contain exit
           status/code information of the main process of the service. For the
           precise definition of the exit code and status, see wait(2).
           $EXIT_CODE is one of "exited", "killed", "dumped".  $EXIT_STATUS
           contains the numeric exit code formatted as string if $EXIT_CODE is
           "exited", and the signal name in all other cases. Note that these
           environment variables are only set if the service manager succeeded
           to start and identify the main process of the service.

           Table 6. Summary of possible service result variable values
           ┌──────────────────┬──────────────────┬─────────────────────┐
           │$SERVICE_RESULT   $EXIT_CODE       $EXIT_STATUS        │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"success"         │ "killed"         │ "HUP", "INT",       │
           │                  │                  │ "TERM", "PIPE"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0"                 │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"protocol"        │ not set          │ not set             │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0"                 │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"timeout"         │ "killed"         │ "TERM", "KILL"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0", "1", "2", "3", │
           │                  │                  │ ..., "255"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"exit-code"       │ "exited"         │ "1", "2", "3", ..., │
           │                  │                  │ "255"               │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"signal"          │ "killed"         │ "HUP", "INT",       │
           │                  │                  │ "KILL", ...         │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"core-dump"       │ "dumped"         │ "ABRT", "SEGV",     │
           │                  │                  │ "QUIT", ...         │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"watchdog"        │ "dumped"         │ "ABRT"              │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "killed"         │ "TERM", "KILL"      │
           │                  ├──────────────────┼─────────────────────┤
           │                  │ "exited"         │ "0", "1", "2", "3", │
           │                  │                  │ ..., "255"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"exec-condition"  │ "exited"         │ "1", "2", "3", "4", │
           │                  │                  │ ..., "254"          │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"oom-kill"        │ "killed"         │ "TERM", "KILL"      │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"start-limit-hit" │ not set          │ not set             │
           ├──────────────────┼──────────────────┼─────────────────────┤
           │"resources"       │ any of the above │ any of the above    │
           ├──────────────────┴──────────────────┴─────────────────────┤
           │Note: the process may be also terminated by a signal not   │
           │sent by systemd. In particular the process may send an     │
           │arbitrary signal to itself in a handler for any of the     │
           │non-maskable signals. Nevertheless, in the "timeout" and   │
           │"watchdog" rows above only the signals that systemd sends  │
           │have been included. Moreover, using SuccessExitStatus=     │
           │additional exit statuses may be declared to indicate clean │
           │termination, which is not reflected by this table.         │
           └───────────────────────────────────────────────────────────┘

       $PIDFILE
           The path to the configured PID file, in case the process is forked
           off on behalf of a service that uses the PIDFile= setting, see
           systemd.service(5) for details. Service code may use this environment
           variable to automatically generate a PID file at the location
           configured in the unit file. This field is set to an absolute path in
           the file system.

       For system services, when PAMName= is enabled and pam_systemd is part of
       the selected PAM stack, additional environment variables defined by
       systemd may be set for services. Specifically, these are $XDG_SEAT,
       $XDG_VTNR, see pam_systemd(8) for details.

PROCESS EXIT CODES
       When invoking a unit process the service manager possibly fails to apply
       the execution parameters configured with the settings above. In that case
       the already created service process will exit with a non-zero exit code
       before the configured command line is executed. (Or in other words, the
       child process possibly exits with these error codes, after having been
       created by the fork(2) system call, but before the matching execve(2)
       system call is called.) Specifically, exit codes defined by the C
       library, by the LSB specification and by the systemd service manager
       itself are used.

       The following basic service exit codes are defined by the C library.

       Table 7. Basic C library exit codes
       ┌──────────┬───────────────┬────────────────────┐
       │Exit Code Symbolic Name Description        │
       ├──────────┼───────────────┼────────────────────┤
       │0         │ EXIT_SUCCESS  │ Generic success    │
       │          │               │ code.              │
       ├──────────┼───────────────┼────────────────────┤
       │1         │ EXIT_FAILURE  │ Generic failure or │
       │          │               │ unspecified error. │
       └──────────┴───────────────┴────────────────────┘

       The following service exit codes are defined by the LSB
       specification[10].

       Table 8. LSB service exit codes
       ┌──────────┬──────────────────────┬────────────────────┐
       │Exit Code Symbolic Name        Description        │
       ├──────────┼──────────────────────┼────────────────────┤
       │2         │ EXIT_INVALIDARGUMENT │ Invalid or excess  │
       │          │                      │ arguments.         │
       ├──────────┼──────────────────────┼────────────────────┤
       │3         │ EXIT_NOTIMPLEMENTED  │ Unimplemented      │
       │          │                      │ feature.           │
       ├──────────┼──────────────────────┼────────────────────┤
       │4         │ EXIT_NOPERMISSION    │ The user has       │
       │          │                      │ insufficient       │
       │          │                      │ privileges.        │
       ├──────────┼──────────────────────┼────────────────────┤
       │5         │ EXIT_NOTINSTALLED    │ The program is not │
       │          │                      │ installed.         │
       ├──────────┼──────────────────────┼────────────────────┤
       │6         │ EXIT_NOTCONFIGURED   │ The program is not │
       │          │                      │ configured.        │
       ├──────────┼──────────────────────┼────────────────────┤
       │7         │ EXIT_NOTRUNNING      │ The program is not │
       │          │                      │ running.           │
       └──────────┴──────────────────────┴────────────────────┘

       The LSB specification suggests that error codes 200 and above are
       reserved for implementations. Some of them are used by the service
       manager to indicate problems during process invocation:

       Table 9. systemd-specific exit codes
       ┌──────────┬──────────────────────────────┬─────────────────────────────────────────────┐
       │Exit Code Symbolic Name                Description                                 │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │200       │ EXIT_CHDIR                   │ Changing to the                             │
       │          │                              │ requested working                           │
       │          │                              │ directory failed.                           │
       │          │                              │ See                                         │
       │          │                              │ WorkingDirectory=                           │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │201       │ EXIT_NICE                    │ Failed to set up                            │
       │          │                              │ process scheduling                          │
       │          │                              │ priority (nice                              │
       │          │                              │ level). See Nice=                           │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │202       │ EXIT_FDS                     │ Failed to close                             │
       │          │                              │ unwanted file                               │
       │          │                              │ descriptors, or to                          │
       │          │                              │ adjust passed file                          │
       │          │                              │ descriptors.                                │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │203       │ EXIT_EXEC                    │ The actual process                          │
       │          │                              │ execution failed                            │
       │          │                              │ (specifically, the                          │
       │          │                              │ execve(2) system                            │
       │          │                              │ call). Most likely                          │
       │          │                              │ this is caused by a                         │
       │          │                              │ missing or                                  │
       │          │                              │ non-accessible                              │
       │          │                              │ executable file.                            │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │204       │ EXIT_MEMORY                  │ Failed to perform an                        │
       │          │                              │ action due to memory                        │
       │          │                              │ shortage.                                   │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │205       │ EXIT_LIMITS                  │ Failed to adjust                            │
       │          │                              │ resource limits. See                        │
       │          │                              │ LimitCPU= and                               │
       │          │                              │ related settings                            │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │206       │ EXIT_OOM_ADJUST              │ Failed to adjust the                        │
       │          │                              │ OOM setting. See                            │
       │          │                              │ OOMScoreAdjust=                             │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │207       │ EXIT_SIGNAL_MASK             │ Failed to set                               │
       │          │                              │ process signal mask.                        │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │208       │ EXIT_STDIN                   │ Failed to set up                            │
       │          │                              │ standard input. See                         │
       │          │                              │ StandardInput=                              │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │209       │ EXIT_STDOUT                  │ Failed to set up                            │
       │          │                              │ standard output. See                        │
       │          │                              │ StandardOutput=                             │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │210       │ EXIT_CHROOT                  │ Failed to change                            │
       │          │                              │ root directory                              │
       │          │                              │ (chroot(2)). See                            │
       │          │                              │ RootDirectory=/RootImage=                   │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │211       │ EXIT_IOPRIO                  │ Failed to set up IO                         │
       │          │                              │ scheduling priority. See                    │
       │          │                              │ IOSchedulingClass=/IOSchedulingPriority=    │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │212       │ EXIT_TIMERSLACK              │ Failed to set up timer slack. See           │
       │          │                              │ TimerSlackNSec= above.                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │213       │ EXIT_SECUREBITS              │ Failed to set process secure bits. See      │
       │          │                              │ SecureBits= above.                          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │214       │ EXIT_SETSCHEDULER            │ Failed to set up CPU scheduling. See        │
       │          │                              │ CPUSchedulingPolicy=/CPUSchedulingPriority= │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │215       │ EXIT_CPUAFFINITY             │ Failed to set up CPU affinity. See          │
       │          │                              │ CPUAffinity= above.                         │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │216       │ EXIT_GROUP                   │ Failed to determine or change group         │
       │          │                              │ credentials. See                            │
       │          │                              │ Group=/SupplementaryGroups= above.          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │217       │ EXIT_USER                    │ Failed to determine or change user          │
       │          │                              │ credentials, or to set up user namespacing. │
       │          │                              │ See User=/PrivateUsers= above.              │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │218       │ EXIT_CAPABILITIES            │ Failed to drop capabilities, or apply       │
       │          │                              │ ambient capabilities. See                   │
       │          │                              │ CapabilityBoundingSet=/AmbientCapabilities= │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │219       │ EXIT_CGROUP                  │ Setting up the service control group        │
       │          │                              │ failed.                                     │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │220       │ EXIT_SETSID                  │ Failed to create new process session.       │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │221       │ EXIT_CONFIRM                 │ Execution has been cancelled by the user.   │
       │          │                              │ See the systemd.confirm_spawn= kernel       │
       │          │                              │ command line setting on kernel-command-     │
       │          │                              │ line(7) for details.                        │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │222       │ EXIT_STDERR                  │ Failed to set up standard error output. See │
       │          │                              │ StandardError= above.                       │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │224       │ EXIT_PAM                     │ Failed to set up PAM session. See PAMName=  │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │225       │ EXIT_NETWORK                 │ Failed to set up network namespacing. See   │
       │          │                              │ PrivateNetwork= above.                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │226       │ EXIT_NAMESPACE               │ Failed to set up mount namespacing. See     │
       │          │                              │ ReadOnlyPaths= and related settings above.  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │227       │ EXIT_NO_NEW_PRIVILEGES       │ Failed to disable new privileges. See       │
       │          │                              │ NoNewPrivileges=yes above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │228       │ EXIT_SECCOMP                 │ Failed to apply system call filters. See    │
       │          │                              │ SystemCallFilter= and related settings      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │229       │ EXIT_SELINUX_CONTEXT         │ Determining or changing SELinux context     │
       │          │                              │ failed. See SELinuxContext= above.          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │230       │ EXIT_PERSONALITY             │ Failed to set up an execution domain        │
       │          │                              │ (personality). See Personality= above.      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │231       │ EXIT_APPARMOR_PROFILE        │ Failed to prepare changing AppArmor         │
       │          │                              │ profile. See AppArmorProfile= above.        │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │232       │ EXIT_ADDRESS_FAMILIES        │ Failed to restrict address families. See    │
       │          │                              │ RestrictAddressFamilies= above.             │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │233       │ EXIT_RUNTIME_DIRECTORY       │ Setting up runtime directory failed. See    │
       │          │                              │ RuntimeDirectory= and related settings      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │235       │ EXIT_CHOWN                   │ Failed to adjust socket ownership. Used for │
       │          │                              │ socket units only.                          │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │236       │ EXIT_SMACK_PROCESS_LABEL     │ Failed to set SMACK label. See              │
       │          │                              │ SmackProcessLabel= above.                   │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │237       │ EXIT_KEYRING                 │ Failed to set up kernel keyring.            │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │238       │ EXIT_STATE_DIRECTORY         │ Failed to set up unit's state directory.    │
       │          │                              │ See StateDirectory= above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │239       │ EXIT_CACHE_DIRECTORY         │ Failed to set up unit's cache directory.    │
       │          │                              │ See CacheDirectory= above.                  │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │240       │ EXIT_LOGS_DIRECTORY          │ Failed to set up unit's logging directory.  │
       │          │                              │ See LogsDirectory= above.                   │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │241       │ EXIT_CONFIGURATION_DIRECTORY │ Failed to set up unit's configuration       │
       │          │                              │ directory. See ConfigurationDirectory=      │
       │          │                              │ above.                                      │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │242       │ EXIT_NUMA_POLICY             │ Failed to set up unit's NUMA memory policy. │
       │          │                              │ See NUMAPolicy= and NUMAMask= above.        │
       ├──────────┼──────────────────────────────┼─────────────────────────────────────────────┤
       │243       │ EXIT_CREDENTIALS             │ Failed to set up unit's credentials. See    │
       │          │                              │ LoadCredential= and SetCredential= above.   │
       └──────────┴──────────────────────────────┴─────────────────────────────────────────────┘

       Finally, the BSD operating systems define a set of exit codes, typically
       defined on Linux systems too:

       Table 10. BSD exit codes
       ┌──────────┬────────────────┬─────────────────────┐
       │Exit Code Symbolic Name  Description         │
       ├──────────┼────────────────┼─────────────────────┤
       │64        │ EX_USAGE       │ Command line usage  │
       │          │                │ error               │
       ├──────────┼────────────────┼─────────────────────┤
       │65        │ EX_DATAERR     │ Data format error   │
       ├──────────┼────────────────┼─────────────────────┤
       │66        │ EX_NOINPUT     │ Cannot open input   │
       ├──────────┼────────────────┼─────────────────────┤
       │67        │ EX_NOUSER      │ Addressee unknown   │
       ├──────────┼────────────────┼─────────────────────┤
       │68        │ EX_NOHOST      │ Host name unknown   │
       ├──────────┼────────────────┼─────────────────────┤
       │69        │ EX_UNAVAILABLE │ Service unavailable │
       ├──────────┼────────────────┼─────────────────────┤
       │70        │ EX_SOFTWARE    │ internal software   │
       │          │                │ error               │
       ├──────────┼────────────────┼─────────────────────┤
       │71        │ EX_OSERR       │ System error (e.g., │
       │          │                │ can't fork)         │
       ├──────────┼────────────────┼─────────────────────┤
       │72        │ EX_OSFILE      │ Critical OS file    │
       │          │                │ missing             │
       ├──────────┼────────────────┼─────────────────────┤
       │73        │ EX_CANTCREAT   │ Can't create (user) │
       │          │                │ output file         │
       ├──────────┼────────────────┼─────────────────────┤
       │74        │ EX_IOERR       │ Input/output error  │
       ├──────────┼────────────────┼─────────────────────┤
       │75        │ EX_TEMPFAIL    │ Temporary failure;  │
       │          │                │ user is invited to  │
       │          │                │ retry               │
       ├──────────┼────────────────┼─────────────────────┤
       │76        │ EX_PROTOCOL    │ Remote error in     │
       │          │                │ protocol            │
       ├──────────┼────────────────┼─────────────────────┤
       │77        │ EX_NOPERM      │ Permission denied   │
       ├──────────┼────────────────┼─────────────────────┤
       │78        │ EX_CONFIG      │ Configuration error │
       └──────────┴────────────────┴─────────────────────┘

SEE ALSO
       systemd(1), systemctl(1), systemd-analyze(1), journalctl(1), systemd-
       system.conf(5), systemd.unit(5), systemd.service(5), systemd.socket(5),
       systemd.swap(5), systemd.mount(5), systemd.kill(5), systemd.resource-
       control(5), systemd.time(7), systemd.directives(7), tmpfiles.d(5),
       exec(3), fork(2)

NOTES
        1. Discoverable Partitions Specification
           https://systemd.io/DISCOVERABLE_PARTITIONS

        2. The /proc Filesystem
           https://www.kernel.org/doc/html/latest/filesystems/proc.html#mount-options

        3. User/Group Name Syntax
           https://systemd.io/USER_NAMES

        4. No New Privileges Flag
           https://www.kernel.org/doc/html/latest/userspace-api/no_new_privs.html

        5. JSON User Record
           https://systemd.io/USER_RECORD

        6. proc.txt
           https://www.kernel.org/doc/Documentation/filesystems/proc.txt

        7. C escapes
           https://en.wikipedia.org/wiki/Escape_sequences_in_C#Table_of_escape_sequences

        8. most control characters
           https://en.wikipedia.org/wiki/Control_character#In_ASCII

        9. Base64
           https://tools.ietf.org/html/rfc2045#section-6.8

       10. LSB specification
           https://refspecs.linuxbase.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/iniscrptact.html



systemd 247                                                      SYSTEMD.EXEC(5)