PAM_SYSTEMD(8)                     pam_systemd                    PAM_SYSTEMD(8)

       pam_systemd - Register user sessions in the systemd login manager


       pam_systemd registers user sessions with the systemd login manager
       systemd-logind.service(8), and hence the systemd control group hierarchy.

       The module also applies various resource management and runtime
       parameters to the new session, as configured in the JSON User Record[1]
       of the user, when one is defined.

       On login, this module — in conjunction with systemd-logind.service —
       ensures the following:

        1. If it does not exist yet, the user runtime directory /run/user/$UID
           is either created or mounted as new "tmpfs" file system with quota
           applied, and its ownership changed to the user that is logging in.

        2. The $XDG_SESSION_ID environment variable is initialized. If auditing
           is available and was run before this module (which is
           highly recommended), the variable is initialized from the auditing
           session id (/proc/self/sessionid). Otherwise, an independent session
           counter is used.

        3. A new systemd scope unit is created for the session. If this is the
           first concurrent session of the user, an implicit per-user slice unit
           below user.slice is automatically created and the scope placed into
           it. An instance of the system service user@.service, which runs the
           systemd user manager instance, is started.

        4. The "$TZ", "$EMAIL" and "$LANG" environment variables are configured
           for the user, based on the respective data from the user's JSON
           record (if it is defined). Moreover, any environment variables
           explicitly configured in the user record are imported, and the umask,
           nice level, and resource limits initialized.

       On logout, this module ensures the following:

        1. If enabled in logind.conf(5) (KillUserProcesses=), all processes of
           the session are terminated. If the last concurrent session of a user
           ends, the user's systemd instance will be terminated too, and so will
           the user's slice unit.

        2. If the last concurrent session of a user ends, the user runtime
           directory /run/user/$UID and all its contents are removed, too.

       If the system was not booted up with systemd as init system, this module
       does nothing and immediately returns PAM_SUCCESS.

       The following options are understood:

           Takes a string argument which sets the session class. The
           XDG_SESSION_CLASS environment variable (see below) takes precedence.
           One of "user", "greeter", "lock-screen" or "background". See
           sd_session_get_class(3) for details about the session class.

           Takes a string argument which sets the session type. The
           XDG_SESSION_TYPE environment variable (see below) takes precedence.
           One of "unspecified", "tty", "x11", "wayland" or "mir". See
           sd_session_get_type(3) for details about the session type.

           Takes a single, short identifier string for the desktop environment.
           The XDG_SESSION_DESKTOP environment variable (see below) takes
           precedence. This may be used to indicate the session desktop used,
           where this applies and if this information is available. For example:
           "GNOME", or "KDE". It is recommended to use the same identifiers and
           capitalization as for $XDG_CURRENT_DESKTOP, as defined by the Desktop
           Entry Specification[2]. (However, note that the option only takes a
           single item, and not a colon-separated list like
           $XDG_CURRENT_DESKTOP.) See sd_session_get_desktop(3) for further

           Takes an optional boolean argument. If yes or without the argument,
           the module will log debugging information as it operates.

       Only session is provided.

       The following environment variables are initialized by the module and
       available to the processes of the user's session:

           A short session identifier, suitable to be used in filenames. The
           string itself should be considered opaque, although often it is just
           the audit session ID as reported by /proc/self/sessionid. Each ID
           will be assigned only once during machine uptime. It may hence be
           used to uniquely label files or other resources of this session.
           Combine this ID with the boot identifier, as returned by
           sd_id128_get_boot(3), for a globally unique identifier.

           Path to a user-private user-writable directory that is bound to the
           user login time on the machine. It is automatically created the first
           time a user logs in and removed on the user's final logout. If a user
           logs in twice at the same time, both sessions will see the same
           $XDG_RUNTIME_DIR and the same contents. If a user logs in once, then
           logs out again, and logs in again, the directory contents will have
           been lost in between, but applications should not rely on this
           behavior and must be able to deal with stale files. To store
           session-private data in this directory, the user should include the
           value of $XDG_SESSION_ID in the filename. This directory shall be
           used for runtime file system objects such as AF_UNIX sockets, FIFOs,
           PID files and similar. It is guaranteed that this directory is local
           and offers the greatest possible file system feature set the
           operating system provides. For further details, see the XDG Base
           Directory Specification[3].  $XDG_RUNTIME_DIR is not set if the
           current user is not the original user of the session.

       $TZ, $EMAIL, $LANG
           If a JSON user record is known for the user logging in these
           variables are initialized from the respective data in the record.

       The following environment variables are read by the module and may be
       used by the PAM service to pass metadata to the module. If these
       variables are not set when the PAM module is invoked but can be
       determined otherwise they are set by the module, so that these variables
       are initialized for the session and applications if known at all.

           The session type. This may be used instead of type= on the module
           parameter line, and is usually preferred.

           The session class. This may be used instead of class= on the module
           parameter line, and is usually preferred.

           The desktop identifier. This may be used instead of desktop= on the
           module parameter line, and is usually preferred.

           The seat name the session shall be registered for, if any.

           The VT number the session shall be registered for, if any. (Only
           applies to seats with a VT available, such as "seat0")

       If not set, pam_systemd will initialize $XDG_SEAT and $XDG_VTNR based on
       the $DISPLAY variable (if the latter is set).

       PAM modules earlier in the stack, that is those that come before, can set session scope limits using the PAM context
       objects. The data for these objects is provided as NUL-terminated C
       strings and maps directly to the respective unit resource control
       directives. Note that these limits apply to individual sessions of the
       user, they do not apply to all user processes as a combined whole. In
       particular, the per-user user@.service unit instance, which runs the
       systemd --user manager process and its children, and is tracked outside
       of any session, being shared by all the user's sessions, is not covered
       by these limits.

       See systemd.resource-control(5) for more information about the resources.
       Also, see pam_set_data(3) for additional information about how to set the
       context objects.

           Sets unit MemoryMax=.

           Sets unit TasksMax=.

           Sets unit CPUWeight=.

           Sets unit IOWeight=.

           Sets unit RuntimeMaxSec=.

       Example data as can be provided from an another PAM module:

           pam_set_data(handle, "systemd.memory_max", (void *)"200M", cleanup);
           pam_set_data(handle, "systemd.tasks_max",  (void *)"50",   cleanup);
           pam_set_data(handle, "systemd.cpu_weight", (void *)"100",  cleanup);
           pam_set_data(handle, "systemd.io_weight",  (void *)"340",  cleanup);
           pam_set_data(handle, "systemd.runtime_max_sec", (void *)"3600", cleanup);

       Here's an example PAM configuration fragment that allows users sessions
       to be managed by systemd-logind.service:

           auth      sufficient
           -auth     sufficient
           auth      required

           account   required
           -account  sufficient
           account   sufficient
           account   required

           -password sufficient
           password  sufficient sha512 shadow try_first_pass try_authtok
           password  required

           -session  optional revoke
           -session  optional
           -session  optional
           -session  optional
           session   required

       systemd(1), systemd-logind.service(8), logind.conf(5), loginctl(1),
       pam_systemd_home(8), pam.conf(5), pam.d(5), pam(8), pam_loginuid(8),
       systemd.scope(5), systemd.slice(5), systemd.service(5)

        1. JSON User Record

        2. Desktop Entry Specification

        3. XDG Base Directory Specification

systemd 247                                                       PAM_SYSTEMD(8)