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6 This file is part of systemd.
8 Copyright 2010 Lennart Poettering
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11 under the terms of the GNU Lesser General Public License as published by
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24 <refentry id="systemd.journal-fields">
27 <title>systemd.journal-fields</title>
28 <productname>systemd</productname>
32 <contrib>Developer</contrib>
33 <firstname>Lennart</firstname>
34 <surname>Poettering</surname>
35 <email>lennart@poettering.net</email>
41 <refentrytitle>systemd.journal-fields</refentrytitle>
42 <manvolnum>7</manvolnum>
46 <refname>systemd.journal-fields</refname>
47 <refpurpose>Special journal fields</refpurpose>
51 <title>Description</title>
53 <para>Entries in the journal resemble an environment
54 block in their syntax, however with fields that can
55 include binary data. Primarily, fields are formatted
56 UTF-8 text strings, and binary formatting is used only
57 where formatting as UTF-8 text strings makes little
58 sense. New fields may freely be defined by
59 applications, but a few fields have special
60 meaning. All fields with special meanings are
61 optional. In some cases fields may appear more than
62 once per entry.</para>
66 <title>User Journal Fields</title>
68 <para>User fields are fields that are directly passed
69 from clients and stored in the journal.</para>
71 <variablelist class='journal-directives'>
73 <term><varname>MESSAGE=</varname></term>
75 <para>The human-readable
76 message string for this
77 entry. This is supposed to be
78 the primary text shown to the
79 user. It is usually not
80 translated (but might be in
81 some cases), and is not
82 supposed to be parsed for meta
88 <term><varname>MESSAGE_ID=</varname></term>
90 <para>A 128-bit message
91 identifier ID for recognizing
92 certain message types, if this
93 is desirable. This should
94 contain a 128-bit ID formatted
95 as a lower-case hexadecimal
96 string, without any separating
97 dashes or suchlike. This is
99 UUID-compatible ID, but this is not
100 enforced, and formatted
101 differently. Developers can
102 generate a new ID for this
103 purpose with <command>journalctl
104 <option>--new-id</option></command>.
110 <term><varname>PRIORITY=</varname></term>
112 <para>A priority value between
113 0 (<literal>emerg</literal>)
115 (<literal>debug</literal>)
116 formatted as a decimal
117 string. This field is
118 compatible with syslog's
119 priority concept.</para>
124 <term><varname>CODE_FILE=</varname></term>
125 <term><varname>CODE_LINE=</varname></term>
126 <term><varname>CODE_FUNC=</varname></term>
128 <para>The code location
129 generating this message, if
130 known. Contains the source
131 filename, the line number and
132 the function name.</para>
137 <term><varname>ERRNO=</varname></term>
139 <para>The low-level Unix error
140 number causing this entry, if
141 any. Contains the numeric
143 <citerefentry><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
144 formatted as a decimal
150 <term><varname>SYSLOG_FACILITY=</varname></term>
151 <term><varname>SYSLOG_IDENTIFIER=</varname></term>
152 <term><varname>SYSLOG_PID=</varname></term>
154 <para>Syslog compatibility
155 fields containing the facility
156 (formatted as decimal string),
157 the identifier string
158 (i.e. "tag"), and the client
167 <title>Trusted Journal Fields</title>
169 <para>Fields prefixed with an underscore are trusted
170 fields, i.e. fields that are implicitly added by the
171 journal and cannot be altered by client code.</para>
173 <variablelist class='journal-directives'>
175 <term><varname>_PID=</varname></term>
176 <term><varname>_UID=</varname></term>
177 <term><varname>_GID=</varname></term>
179 <para>The process, user and
180 group ID of the process the
181 journal entry originates from
182 formatted as a decimal
188 <term><varname>_COMM=</varname></term>
189 <term><varname>_EXE=</varname></term>
190 <term><varname>_CMDLINE=</varname></term>
192 <para>The name, the executable
193 path and the command line of
194 the process the journal entry
195 originates from.</para>
200 <term><varname>_CAP_EFFECTIVE=</varname></term>
202 <para>The effective <citerefentry><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry> of
203 the process the journal entry
204 originates from.</para>
209 <term><varname>_AUDIT_SESSION=</varname></term>
210 <term><varname>_AUDIT_LOGINUID=</varname></term>
212 <para>The session and login
213 UID of the process the journal
214 entry originates from, as
215 maintained by the kernel audit
221 <term><varname>_SYSTEMD_CGROUP=</varname></term>
222 <term><varname>_SYSTEMD_SESSION=</varname></term>
223 <term><varname>_SYSTEMD_UNIT=</varname></term>
224 <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
225 <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
228 <para>The control group path in
229 the systemd hierarchy, the
230 systemd session ID (if any),
231 the systemd unit name (if any),
232 the systemd user session unit name (if any)
233 and the owner UID of the
234 systemd session (if any) of
235 the process the journal entry
236 originates from.</para>
241 <term><varname>_SELINUX_CONTEXT=</varname></term>
243 <para>The SELinux security
244 context of the process the
245 journal entry originates
251 <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
253 <para>The earliest trusted
254 timestamp of the message, if
255 any is known that is different
256 from the reception time of the
257 journal. This is the time in
258 microseconds since the epoch UTC,
259 formatted as a decimal
265 <term><varname>_BOOT_ID=</varname></term>
267 <para>The kernel boot ID for
268 the boot the message was
269 generated in, formatted as
270 a 128-bit hexadecimal
276 <term><varname>_MACHINE_ID=</varname></term>
278 <para>The machine ID of the
279 originating host, as available
281 <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
286 <term><varname>_HOSTNAME=</varname></term>
288 <para>The name of the
289 originating host.</para>
294 <term><varname>_TRANSPORT=</varname></term>
296 <para>How the entry was
297 received by the journal
298 service. Valid transports are:
303 <option>driver</option>
316 <option>syslog</option>
330 <option>journal</option>
343 <option>stdout</option>
357 <option>kernel</option>
373 <title>Kernel Journal Fields</title>
375 <para>Kernel fields are fields that are used by
376 messages originating in the kernel and stored in the
379 <variablelist class='journal-directives'>
381 <term><varname>_KERNEL_DEVICE=</varname></term>
383 <para>The kernel device
384 name. If the entry is
385 associated to a block device,
386 the major and minor of the
387 device node, separated by <literal>:</literal>
388 and prefixed by <literal>b</literal>. Similar
389 for character devices, but
390 prefixed by <literal>c</literal>. For network
391 devices the interface index,
392 prefixed by <literal>n</literal>. For all other
393 devices <literal>+</literal> followed by the
394 subsystem name, followed by
395 <literal>:</literal>, followed by the kernel
400 <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
402 <para>The kernel subsystem name.</para>
406 <term><varname>_UDEV_SYSNAME=</varname></term>
408 <para>The kernel device name
409 as it shows up in the device
411 <filename>/sys</filename>.</para>
415 <term><varname>_UDEV_DEVNODE=</varname></term>
417 <para>The device node path of
419 <filename>/dev</filename>.</para>
423 <term><varname>_UDEV_DEVLINK=</varname></term>
425 <para>Additional symlink names
426 pointing to the device node in
427 <filename>/dev</filename>. This
428 field is frequently set more
429 than once per entry.</para>
436 <title>Fields to log on behalf of a different program</title>
438 <para>Fields in this section are used by programs
439 to specify that they are logging on behalf of another
443 <para>Fields used by the <command>systemd-coredump</command>
444 coredump kernel helper:
447 <variablelist class='journal-directives'>
449 <term><varname>COREDUMP_UNIT=</varname></term>
450 <term><varname>COREDUMP_USER_UNIT=</varname></term>
452 <para>Used to annotate
453 messages containing coredumps from
454 system and session units.
456 <citerefentry><refentrytitle>systemd-coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
462 <para>Priviledged programs (currently UID 0) may
463 attach <varname>OBJECT_PID=</varname> to a
464 message. This will instruct
465 <command>systemd-journald</command> to attach
466 additional fields on behalf of the caller:</para>
468 <variablelist class='journal-directives'>
470 <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
472 <para>PID of the program that this
479 <term><varname>OBJECT_UID=</varname></term>
480 <term><varname>OBJECT_GID=</varname></term>
481 <term><varname>OBJECT_COMM=</varname></term>
482 <term><varname>OBJECT_EXE=</varname></term>
483 <term><varname>OBJECT_CMDLINE=</varname></term>
484 <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
485 <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
486 <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
487 <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
488 <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
489 <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
490 <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
492 <para>These are additional fields added automatically
493 by <command>systemd-journald</command>.
494 Their meaning is the same as
495 <varname>_UID=</varname>,
496 <varname>_GID=</varname>,
497 <varname>_COMM=</varname>,
498 <varname>_EXE=</varname>,
499 <varname>_CMDLINE=</varname>,
500 <varname>_AUDIT_SESSION=</varname>,
501 <varname>_AUDIT_LOGINUID=</varname>,
502 <varname>_SYSTEMD_CGROUP=</varname>,
503 <varname>_SYSTEMD_SESSION=</varname>,
504 <varname>_SYSTEMD_UNIT=</varname>,
505 <varname>_SYSTEMD_USER_UNIT=</varname>, and
506 <varname>_SYSTEMD_OWNER_UID=</varname>
507 as described above, except that the
508 process identified by <replaceable>PID</replaceable>
509 is described, instead of the process
510 which logged the message.</para>
519 <title>Address Fields</title>
521 <para>During serialization into external formats, such
523 url="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
524 Export Format</ulink> or the <ulink
525 url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
526 JSON Format</ulink>, the addresses of journal entries
527 are serialized into fields prefixed with double
528 underscores. Note that these aren't proper fields when
529 stored in the journal but for addressing meta data of
530 entries. They cannot be written as part of structured
531 log entries via calls such as
532 <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>. They
533 may also not be used as matches for
534 <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
536 <variablelist class='journal-directives'>
538 <term><varname>__CURSOR=</varname></term>
540 <para>The cursor for the
541 entry. A cursor is an opaque
542 text string that uniquely
543 describes the position of an
544 entry in the journal and is
545 portable across machines,
546 platforms and journal files.
552 <term><varname>__REALTIME_TIMESTAMP=</varname></term>
554 <para>The wallclock time
555 (<constant>CLOCK_REALTIME</constant>)
556 at the point in time the entry
557 was received by the journal,
558 in microseconds since the epoch
559 UTC, formatted as a decimal
560 string. This has different
562 <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>,
563 as it is usually a bit later
564 but more likely to be monotonic.
570 <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
572 <para>The monotonic time
573 (<constant>CLOCK_MONOTONIC</constant>)
574 at the point in time the entry
575 was received by the journal in
576 microseconds, formatted as a decimal
577 string. To be useful as an
578 address for the entry, this
579 should be combined with with the
580 boot ID in <literal>_BOOT_ID=</literal>.
588 <title>See Also</title>
590 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
591 <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
592 <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
593 <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
594 <citerefentry><refentrytitle>systemd-coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
595 <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>