Ubuntu Manpage: systemd.journal-fields

Provided by: systemd_204-5ubuntu20.31_amd64

NAME

       systemd.journal-fields - Special journal fields

DESCRIPTION

       Entries in the journal resemble an environment block in their syntax, however 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 meta data.

MESSAGE_ID=
A 128bit message identifier ID for recognizing certain message types, if this is
desirable. This should contain a 128bit id formatted as 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 journalctl --new-id.

PRIORITY=
A priority value between 0 (emerg) and 7 (debug) formatted as 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 file name,
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 decimal string.

SYSLOG_FACILITY=, SYSLOG_IDENTIFIER=, SYSLOG_PID=
Syslog compatibility fields containing the facility (formatted as decimal string), the
identifier string (i.e. "tag"), and the client PID.

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 decimal string.

_COMM=, _EXE=, _CMDLINE=
The name, the executable path and the command line 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_SESSION=, _SYSTEMD_UNIT=, _SYSTEMD_USER_UNIT=,
_SYSTEMD_OWNER_UID=
The control group path in the systemd hierarchy, the systemd session ID (if any), the
systemd unit name (if any), the systemd user session unit name (if any) and the owner
UID of the systemd session (if any) of the process the journal entry originates from.

_SELINUX_CONTEXT=
The SELinux security context 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 usec since the epoch UTC
formatted as decimal string.

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

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

_HOSTNAME=
The name of the originating host.

_TRANSPORT=
How the entry was received by the journal service. One of driver, syslog, journal,
stdout, kernel for internally generated messages, for those received via the local
syslog socket with the syslog protocol, for those received via the native journal
protocol, for the those read from a services' standard output or error output, or for
those read from the kernel, respectively.

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 the interface index, prefixed by
           'n'. For all other devices '+' followed by the subsystem name, 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.

SPECIAL JOURNAL FIELDS

       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
           systemd-coredumpctl(1).

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 aren't proper fields when stored in the
       journal, but addressing meta data 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 usec since the epoch UTC formatted as 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 usec formatted as decimal string. To be useful as an address for the
           entry this should be combined with with boot ID in _BOOT_ID=.

NOTES

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

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