systemd.journal-fields

SYSTEMD.JOURNAL-FIELDS(7)    systemd.journal-fields    SYSTEMD.JOURNAL-FIELDS(7)



NAME
       systemd.journal-fields - Special journal fields

DESCRIPTION
       Entries in the journal (as written by systemd-journald.service(8))
       resemble a UNIX process environment block in syntax but with fields that
       may include binary data. Primarily, fields are formatted UTF-8 text
       strings, and binary encoding is used only where formatting as UTF-8 text
       strings makes little sense. New fields may freely be defined by
       applications, but a few fields have special meanings. All fields with
       special meanings are optional. In some cases, fields may appear more than
       once per entry.

USER JOURNAL FIELDS
       User fields are fields that are directly passed from clients and stored
       in the journal.

       MESSAGE=
           The human-readable message string for this entry. This is supposed to
           be the primary text shown to the user. It is usually not translated
           (but might be in some cases), and is not supposed to be parsed for
           metadata.

       MESSAGE_ID=
           A 128-bit message identifier ID for recognizing certain message
           types, if this is desirable. This should contain a 128-bit ID
           formatted as a lower-case hexadecimal string, without any separating
           dashes or suchlike. This is recommended to be a UUID-compatible ID,
           but this is not enforced, and formatted differently. Developers can
           generate a new ID for this purpose with systemd-id128 new.

       PRIORITY=
           A priority value between 0 ("emerg") and 7 ("debug") formatted as a
           decimal string. This field is compatible with syslog's priority
           concept.

       CODE_FILE=, CODE_LINE=, CODE_FUNC=
           The code location generating this message, if known. Contains the
           source filename, the line number and the function name.

       ERRNO=
           The low-level Unix error number causing this entry, if any. Contains
           the numeric value of errno(3) formatted as a decimal string.

       INVOCATION_ID=, USER_INVOCATION_ID=
           A randomized, unique 128-bit ID identifying each runtime cycle of the
           unit. This is different from _SYSTEMD_INVOCATION_ID in that it is
           only used for messages coming from systemd code (e.g. logs from the
           system/user manager or from forked processes performing
           systemd-related setup).

       SYSLOG_FACILITY=, SYSLOG_IDENTIFIER=, SYSLOG_PID=, SYSLOG_TIMESTAMP=
           Syslog compatibility fields containing the facility (formatted as
           decimal string), the identifier string (i.e. "tag"), the client PID,
           and the timestamp as specified in the original datagram. (Note that
           the tag is usually derived from glibc's program_invocation_short_name
           variable, see program_invocation_short_name(3).)

           Note that the journal service does not validate the values of any
           structured journal fields whose name is not prefixed with an
           underscore, and this includes any syslog related fields such as
           these. Hence, applications that supply a facility, PID, or log level
           are expected to do so properly formatted, i.e. as numeric integers
           formatted as decimal strings.

       SYSLOG_RAW=
           The original contents of the syslog line as received in the syslog
           datagram. This field is only included if the MESSAGE= field was
           modified compared to the original payload or the timestamp could not
           be located properly and is not included in SYSLOG_TIMESTAMP=. Message
           truncation occurs when when the message contains leading or trailing
           whitespace (trailing and leading whitespace is stripped), or it
           contains an embedded NUL byte (the NUL byte and anything after it is
           not included). Thus, the original syslog line is either stored as
           SYSLOG_RAW= or it can be recreated based on the stored priority and
           facility, timestamp, identifier, and the message payload in MESSAGE=.

       DOCUMENTATION=
           A documentation URL with further information about the topic of the
           log message. Tools such as journalctl will include a hyperlink to an
           URL specified this way in their output. Should be a "http://",
           "https://", "file:/", "man:" or "info:" URL.

       TID=
           The numeric thread ID (TID) the log message originates from.

TRUSTED JOURNAL FIELDS
       Fields prefixed with an underscore are trusted fields, i.e. fields that
       are implicitly added by the journal and cannot be altered by client code.

       _PID=, _UID=, _GID=
           The process, user, and group ID of the process the journal entry
           originates from formatted as a decimal string. Note that entries
           obtained via "stdout" or "stderr" of forked processes will contain
           credentials valid for a parent process (that initiated the connection
           to systemd-journald).

       _COMM=, _EXE=, _CMDLINE=
           The name, the executable path, and the command line of the process
           the journal entry originates from.

       _CAP_EFFECTIVE=
           The effective capabilities(7) of the process the journal entry
           originates from.

       _AUDIT_SESSION=, _AUDIT_LOGINUID=
           The session and login UID of the process the journal entry originates
           from, as maintained by the kernel audit subsystem.

       _SYSTEMD_CGROUP=, _SYSTEMD_SLICE=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
       _SYSTEMD_USER_SLICE=, _SYSTEMD_SESSION=, _SYSTEMD_OWNER_UID=
           The control group path in the systemd hierarchy, the systemd slice
           unit name, the systemd unit name, the unit name in the systemd user
           manager (if any), the systemd session ID (if any), and the owner UID
           of the systemd user unit or systemd session (if any) of the process
           the journal entry originates from.

       _SELINUX_CONTEXT=
           The SELinux security context (label) of the process the journal entry
           originates from.

       _SOURCE_REALTIME_TIMESTAMP=
           The earliest trusted timestamp of the message, if any is known that
           is different from the reception time of the journal. This is the time
           in microseconds since the epoch UTC, formatted as a decimal string.

       _BOOT_ID=
           The kernel boot ID for the boot the message was generated in,
           formatted as a 128-bit hexadecimal string.

       _MACHINE_ID=
           The machine ID of the originating host, as available in machine-
           id(5).

       _SYSTEMD_INVOCATION_ID=
           The invocation ID for the runtime cycle of the unit the message was
           generated in, as available to processes of the unit in $INVOCATION_ID
           (see systemd.exec(5)).

       _HOSTNAME=
           The name of the originating host.

       _TRANSPORT=
           How the entry was received by the journal service. Valid transports
           are:

           audit
               for those read from the kernel audit subsystem

           driver
               for internally generated messages

           syslog
               for those received via the local syslog socket with the syslog
               protocol

           journal
               for those received via the native journal protocol

           stdout
               for those read from a service's standard output or error output

           kernel
               for those read from the kernel

       _STREAM_ID=
           Only applies to "_TRANSPORT=stdout" records: specifies a randomized
           128bit ID assigned to the stream connection when it was first
           created. This ID is useful to reconstruct individual log streams from
           the log records: all log records carrying the same stream ID
           originate from the same stream.

       _LINE_BREAK=
           Only applies to "_TRANSPORT=stdout" records: indicates that the log
           message in the standard output/error stream was not terminated with a
           normal newline character ("\n", i.e. ASCII 10). Specifically, when
           set this field is one of nul (in case the line was terminated by a
           NUL byte), line-max (in case the maximum log line length was reached,
           as configured with LineMax= in journald.conf(5)), eof (if this was
           the last log record of a stream and the stream ended without a final
           newline character), or pid-change (if the process which generated the
           log output changed in the middle of a line). Note that this record is
           not generated when a normal newline character was used for marking
           the log line end.

       _NAMESPACE=
           If this file was written by a systemd-journald instance managing a
           journal namespace that is not the default, this field contains the
           namespace identifier. See systemd-journald.service(8) for details
           about journal namespaces.

KERNEL JOURNAL FIELDS
       Kernel fields are fields that are used by messages originating in the
       kernel and stored in the journal.

       _KERNEL_DEVICE=
           The kernel device name. If the entry is associated to a block device,
           contains the major and minor numbers of the device node, separated by
           ":" and prefixed by "b". Similarly for character devices, but
           prefixed by "c". For network devices, this is the interface index
           prefixed by "n". For all other devices, this is the subsystem name
           prefixed by "+", followed by ":", followed by the kernel device name.

       _KERNEL_SUBSYSTEM=
           The kernel subsystem name.

       _UDEV_SYSNAME=
           The kernel device name as it shows up in the device tree below /sys/.

       _UDEV_DEVNODE=
           The device node path of this device in /dev/.

       _UDEV_DEVLINK=
           Additional symlink names pointing to the device node in /dev/. This
           field is frequently set more than once per entry.

FIELDS TO LOG ON BEHALF OF A DIFFERENT PROGRAM
       Fields in this section are used by programs to specify that they are
       logging on behalf of another program or unit.

       Fields used by the systemd-coredump coredump kernel helper:

       COREDUMP_UNIT=, COREDUMP_USER_UNIT=
           Used to annotate messages containing coredumps from system and
           session units. See coredumpctl(1).

       Privileged programs (currently UID 0) may attach OBJECT_PID= to a
       message. This will instruct systemd-journald to attach additional fields
       on behalf of the caller:

       OBJECT_PID=PID
           PID of the program that this message pertains to.

       OBJECT_UID=, OBJECT_GID=, OBJECT_COMM=, OBJECT_EXE=, OBJECT_CMDLINE=,
       OBJECT_AUDIT_SESSION=, OBJECT_AUDIT_LOGINUID=, OBJECT_SYSTEMD_CGROUP=,
       OBJECT_SYSTEMD_SESSION=, OBJECT_SYSTEMD_OWNER_UID=, OBJECT_SYSTEMD_UNIT=,
       OBJECT_SYSTEMD_USER_UNIT=
           These are additional fields added automatically by systemd-journald.
           Their meaning is the same as _UID=, _GID=, _COMM=, _EXE=, _CMDLINE=,
           _AUDIT_SESSION=, _AUDIT_LOGINUID=, _SYSTEMD_CGROUP=,
           _SYSTEMD_SESSION=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=, and
           _SYSTEMD_OWNER_UID= as described above, except that the process
           identified by PID is described, instead of the process which logged
           the message.

ADDRESS FIELDS
       During serialization into external formats, such as the Journal Export
       Format[1] or the Journal JSON Format[2], the addresses of journal entries
       are serialized into fields prefixed with double underscores. Note that
       these are not proper fields when stored in the journal but for addressing
       metadata of entries. They cannot be written as part of structured log
       entries via calls such as sd_journal_send(3). They may also not be used
       as matches for sd_journal_add_match(3).

       __CURSOR=
           The cursor for the entry. A cursor is an opaque text string that
           uniquely describes the position of an entry in the journal and is
           portable across machines, platforms and journal files.

       __REALTIME_TIMESTAMP=
           The wallclock time (CLOCK_REALTIME) at the point in time the entry
           was received by the journal, in microseconds since the epoch UTC,
           formatted as a decimal string. This has different properties from
           "_SOURCE_REALTIME_TIMESTAMP=", as it is usually a bit later but more
           likely to be monotonic.

       __MONOTONIC_TIMESTAMP=
           The monotonic time (CLOCK_MONOTONIC) at the point in time the entry
           was received by the journal in microseconds, formatted as a decimal
           string. To be useful as an address for the entry, this should be
           combined with the boot ID in "_BOOT_ID=".

SEE ALSO
       systemd(1), systemd-journald.service(8), journalctl(1), journald.conf(5),
       sd-journal(3), coredumpctl(1), systemd.directives(7)

NOTES
        1. Journal Export Format
           https://www.freedesktop.org/wiki/Software/systemd/export

        2. Journal JSON Format
           https://www.freedesktop.org/wiki/Software/systemd/json



systemd 247                                            SYSTEMD.JOURNAL-FIELDS(7)