Provided by: systemd_240-6ubuntu9_amd64 bug

NAME

       systemd.journal-fields - Special journal fields

DESCRIPTION

       Entries in the journal resemble an environment block in their syntax but with fields that
       can include binary data. Primarily, fields are formatted UTF-8 text strings, and binary
       formatting 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 meaning. 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.

       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).)

       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=.

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_SESSION=,
       _SYSTEMD_OWNER_UID=
           The control group path in the systemd hierarchy, the 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)) or eof (if this was the last log
           record of a stream and the stream ended without a final newline character). Note that
           this record is not generated when a normal newline character was used for marking the
           log line end.

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, the major and
           minor of the device node, separated by ":" and prefixed by "b". Similar 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), 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