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NAME | DESCRIPTION | USER JOURNAL FIELDS | TRUSTED JOURNAL FIELDS | KERNEL JOURNAL FIELDS | FIELDS TO LOG ON BEHALF OF A DIFFERENT PROGRAM | ADDRESS FIELDS | SEE ALSO | NOTES | COLOPHON |
SYSTEMD.JOURNAL-FIELDS(7) systemd.journal-fields SYSTEMD.JOURNAL-FIELDS(7)
systemd.journal-fields - Special journal fields
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 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.
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 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 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 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.
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=".
systemd(1), systemd-journald.service(8), journalctl(1),
journald.conf(5), sd-journal(3), coredumpctl(1),
systemd.directives(7)
1. Journal Export Format
https://www.freedesktop.org/wiki/Software/systemd/export
2. Journal JSON Format
https://www.freedesktop.org/wiki/Software/systemd/json
This page is part of the systemd (systemd system and service manager)
project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a bug
report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩. This
page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-11.) If you discover any rendering problems in
this HTML version of the page, or you believe there is a better or
more up-to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not part
of the original manual page), send a mail to man-pages@man7.org
systemd 246 SYSTEMD.JOURNAL-FIELDS(7)
Pages that refer to this page: journalctl(1) , logger(1) , sd_bus_creds_get_audit_login_uid(3) , sd_bus_creds_get_audit_session_id(3) , sd_bus_creds_get_cgroup(3) , sd_bus_creds_get_cmdline(3) , sd_bus_creds_get_comm(3) , sd_bus_creds_get_description(3) , sd_bus_creds_get_egid(3) , sd_bus_creds_get_euid(3) , sd_bus_creds_get_exe(3) , sd_bus_creds_get_fsgid(3) , sd_bus_creds_get_fsuid(3) , sd_bus_creds_get_gid(3) , sd_bus_creds_get_owner_uid(3) , sd_bus_creds_get_pid(3) , sd_bus_creds_get_ppid(3) , sd_bus_creds_get_selinux_context(3) , sd_bus_creds_get_session(3) , sd_bus_creds_get_sgid(3) , sd_bus_creds_get_slice(3) , sd_bus_creds_get_suid(3) , sd_bus_creds_get_supplementary_gids(3) , sd_bus_creds_get_tid(3) , sd_bus_creds_get_tid_comm(3) , sd_bus_creds_get_tty(3) , sd_bus_creds_get_uid(3) , sd_bus_creds_get_unique_name(3) , sd_bus_creds_get_unit(3) , sd_bus_creds_get_user_slice(3) , sd_bus_creds_get_user_unit(3) , sd_bus_creds_get_well_known_names(3) , sd_bus_creds_has_bounding_cap(3) , sd_bus_creds_has_effective_cap(3) , sd_bus_creds_has_inheritable_cap(3) , sd_bus_creds_has_permitted_cap(3) , sd_journal_add_conjunction(3) , sd_journal_add_disjunction(3) , sd_journal_add_match(3) , sd_journal_enumerate_available_data(3) , sd_journal_enumerate_available_unique(3) , sd_journal_enumerate_data(3) , sd_journal_enumerate_fields(3) , sd_journal_enumerate_unique(3) , sd_journal_flush_matches(3) , sd_journal_foreach_data(3) , SD_JOURNAL_FOREACH_DATA(3) , sd_journal_foreach_field(3) , SD_JOURNAL_FOREACH_FIELD(3) , sd_journal_foreach_unique(3) , SD_JOURNAL_FOREACH_UNIQUE(3) , sd_journal_get_catalog(3) , sd_journal_get_catalog_for_message_id(3) , sd_journal_get_data(3) , sd_journal_get_data_threshold(3) , sd_journal_perror(3) , sd_journal_perror_with_location(3) , sd_journal_print(3) , sd_journal_printv(3) , sd_journal_printv_with_location(3) , sd_journal_print_with_location(3) , sd_journal_query_unique(3) , sd_journal_restart_data(3) , sd_journal_restart_fields(3) , sd_journal_restart_unique(3) , sd_journal_send(3) , sd_journal_sendv(3) , sd_journal_sendv_with_location(3) , sd_journal_send_with_location(3) , sd_journal_set_data_threshold(3) , sd_journal_stream_fd(3) , sd_journal_suppress_location(3) , SD_JOURNAL_SUPPRESS_LOCATION(3) , journald.conf(5) , journald@.conf(5) , journald.conf.d(5) , systemd.exec(5) , 30-systemd-environment-d-generator(7) , systemd.directives(7) , systemd.index(7) , systemd-journald(8) , systemd-journald-audit.socket(8) , systemd-journald-dev-log.socket(8) , systemd-journald.service(8) , systemd-journald@.service(8) , systemd-journald.socket(8) , systemd-journald@.socket(8) , systemd-journald-varlink.socket(8) , systemd-journald-varlink@.socket(8) , systemd-journal-gatewayd(8) , systemd-journal-gatewayd.service(8) , systemd-journal-gatewayd.socket(8)