man/systemd.journal-fields.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="systemd.journal-fields">
   7
   8   <refentryinfo>
   9     <title>systemd.journal-fields</title>
  10     <productname>systemd</productname>
  11   </refentryinfo>
  12
  13   <refmeta>
  14     <refentrytitle>systemd.journal-fields</refentrytitle>
  15     <manvolnum>7</manvolnum>
  16   </refmeta>
  17
  18   <refnamediv>
  19     <refname>systemd.journal-fields</refname>
  20     <refpurpose>Special journal fields</refpurpose>
  21   </refnamediv>
  22
  23   <refsect1>
  24     <title>Description</title>
  25
  26     <para>Entries in the journal (as written by
  27     <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
  28     resemble a UNIX process environment block in syntax but with fields that may include binary data.
  29     Primarily, fields are formatted UTF-8 text strings, and binary encoding is used only where formatting as
  30     UTF-8 text strings makes little sense. New fields may freely be defined by applications, but a few fields
  31     have special meanings. All fields with special meanings are optional. In some cases, fields may appear
  32     more than once per entry.</para>
  33   </refsect1>
  34
  35   <refsect1>
  36     <title>User Journal Fields</title>
  37
  38     <para>User fields are fields that are directly passed from clients
  39     and stored in the journal.</para>
  40
  41     <variablelist class='journal-directives'>
  42       <varlistentry>
  43         <term><varname>MESSAGE=</varname></term>
  44         <listitem>
  45           <para>The human-readable message string for this entry. This
  46           is supposed to be the primary text shown to the user. It is
  47           usually not translated (but might be in some cases), and is
  48           not supposed to be parsed for metadata.</para>
  49         </listitem>
  50       </varlistentry>
  51
  52       <varlistentry>
  53         <term><varname>MESSAGE_ID=</varname></term>
  54         <listitem>
  55           <para>A 128-bit message identifier ID for recognizing certain message types, if this is desirable. This
  56           should contain a 128-bit ID formatted as a lower-case hexadecimal string, without any separating dashes or
  57           suchlike. This is recommended to be a UUID-compatible ID, but this is not enforced, and formatted
  58           differently. Developers can generate a new ID for this purpose with <command>systemd-id128 new</command>.
  59           </para>
  60         </listitem>
  61       </varlistentry>
  62
  63       <varlistentry>
  64         <term><varname>PRIORITY=</varname></term>
  65         <listitem>
  66           <para>A priority value between 0 (<literal>emerg</literal>)
  67           and 7 (<literal>debug</literal>) formatted as a decimal
  68           string. This field is compatible with syslog's priority
  69           concept.</para>
  70         </listitem>
  71       </varlistentry>
  72
  73       <varlistentry>
  74         <term><varname>CODE_FILE=</varname></term>
  75         <term><varname>CODE_LINE=</varname></term>
  76         <term><varname>CODE_FUNC=</varname></term>
  77         <listitem>
  78           <para>The code location generating this message, if known.
  79           Contains the source filename, the line number and the
  80           function name.</para>
  81         </listitem>
  82       </varlistentry>
  83
  84       <varlistentry>
  85         <term><varname>ERRNO=</varname></term>
  86         <listitem>
  87           <para>The low-level Unix error number causing this entry, if
  88           any. Contains the numeric value of
  89           <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
  90           formatted as a decimal string.</para>
  91         </listitem>
  92       </varlistentry>
  93
  94       <varlistentry>
  95         <term><varname>INVOCATION_ID=</varname></term>
  96         <term><varname>USER_INVOCATION_ID=</varname></term>
  97         <listitem>
  98           <para>A randomized, unique 128-bit ID identifying each runtime cycle of the unit. This is different from
  99           <varname>_SYSTEMD_INVOCATION_ID</varname> in that it is only used for messages coming from systemd code
 100           (e.g. logs from the system/user manager or from forked processes performing systemd-related setup).</para>
 101         </listitem>
 102       </varlistentry>
 103
 104       <varlistentry>
 105         <term><varname>SYSLOG_FACILITY=</varname></term>
 106         <term><varname>SYSLOG_IDENTIFIER=</varname></term>
 107         <term><varname>SYSLOG_PID=</varname></term>
 108         <term><varname>SYSLOG_TIMESTAMP=</varname></term>
 109         <listitem>
 110           <para>Syslog compatibility fields containing the facility (formatted as
 111           decimal string), the identifier string (i.e.  "tag"), the client PID, and
 112           the timestamp as specified in the original datagram. (Note that the tag is
 113           usually derived from glibc's
 114           <varname>program_invocation_short_name</varname> variable, see
 115           <citerefentry project='die-net'><refentrytitle>program_invocation_short_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.)</para>
 116           <para>Note that the journal service does not validate the values of any structured
 117           journal fields whose name is not prefixed with an underscore, and this includes any
 118           syslog related fields such as these. Hence, applications that supply a facility, PID,
 119           or log level are expected to do so properly formatted, i.e. as numeric integers formatted
 120           as decimal strings.</para>
 121         </listitem>
 122       </varlistentry>
 123
 124       <varlistentry>
 125         <term><varname>SYSLOG_RAW=</varname></term>
 126         <listitem>
 127           <para>The original contents of the syslog line as received in the syslog
 128           datagram. This field is only included if the <varname>MESSAGE=</varname>
 129           field was modified compared to the original payload or the timestamp could
 130           not be located properly and is not included in
 131           <varname>SYSLOG_TIMESTAMP=</varname>. Message truncation occurs when when
 132           the message contains leading or trailing whitespace (trailing and leading
 133           whitespace is stripped), or it contains an embedded
 134           <constant>NUL</constant> byte (the <constant>NUL</constant> byte and
 135           anything after it is not included). Thus, the original syslog line is
 136           either stored as <varname>SYSLOG_RAW=</varname> or it can be recreated
 137           based on the stored priority and facility, timestamp, identifier, and the
 138           message payload in <varname>MESSAGE=</varname>.
 139           </para>
 140         </listitem>
 141       </varlistentry>
 142
 143       <varlistentry>
 144         <term><varname>DOCUMENTATION=</varname></term>
 145         <listitem>
 146           <para>A documentation URL with further information about the topic of the log message. Tools such
 147           as <command>journalctl</command> will include a hyperlink to an URL specified this way in their
 148           output. Should be a <literal>http://</literal>, <literal>https://</literal>,
 149           <literal>file:/</literal>, <literal>man:</literal> or <literal>info:</literal> URL.</para>
 150         </listitem>
 151       </varlistentry>
 152     </variablelist>
 153   </refsect1>
 154
 155   <refsect1>
 156     <title>Trusted Journal Fields</title>
 157
 158     <para>Fields prefixed with an underscore are trusted fields, i.e.
 159     fields that are implicitly added by the journal and cannot be
 160     altered by client code.</para>
 161
 162     <variablelist class='journal-directives'>
 163       <varlistentry>
 164         <term><varname>_PID=</varname></term>
 165         <term><varname>_UID=</varname></term>
 166         <term><varname>_GID=</varname></term>
 167         <listitem>
 168           <para>The process, user, and group ID of the process the
 169           journal entry originates from formatted as a decimal
 170           string. Note that entries obtained via <literal>stdout</literal> or
 171           <literal>stderr</literal> of forked processes will contain credentials valid for a parent
 172           process (that initiated the connection to <command>systemd-journald</command>).</para>
 173         </listitem>
 174       </varlistentry>
 175
 176       <varlistentry>
 177         <term><varname>_COMM=</varname></term>
 178         <term><varname>_EXE=</varname></term>
 179         <term><varname>_CMDLINE=</varname></term>
 180         <listitem>
 181           <para>The name, the executable path, and the command line of
 182           the process the journal entry originates from.</para>
 183         </listitem>
 184       </varlistentry>
 185
 186       <varlistentry>
 187         <term><varname>_CAP_EFFECTIVE=</varname></term>
 188         <listitem>
 189           <para>The effective
 190           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 191           of the process the journal entry originates from.</para>
 192         </listitem>
 193       </varlistentry>
 194
 195       <varlistentry>
 196         <term><varname>_AUDIT_SESSION=</varname></term>
 197         <term><varname>_AUDIT_LOGINUID=</varname></term>
 198         <listitem>
 199           <para>The session and login UID of the process the journal
 200           entry originates from, as maintained by the kernel audit
 201           subsystem.</para>
 202         </listitem>
 203       </varlistentry>
 204
 205       <varlistentry>
 206         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 207         <term><varname>_SYSTEMD_SLICE=</varname></term>
 208         <term><varname>_SYSTEMD_UNIT=</varname></term>
 209         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 210         <term><varname>_SYSTEMD_USER_SLICE=</varname></term>
 211         <term><varname>_SYSTEMD_SESSION=</varname></term>
 212         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 213
 214         <listitem>
 215           <para>The control group path in the systemd hierarchy, the
 216           the systemd slice unit name, the systemd unit name, the
 217           unit name in the systemd user manager (if any), the systemd
 218           session ID (if any), and the owner UID of the systemd user
 219           unit or systemd session (if any) of the process the journal
 220           entry originates from.</para>
 221         </listitem>
 222       </varlistentry>
 223
 224       <varlistentry>
 225         <term><varname>_SELINUX_CONTEXT=</varname></term>
 226         <listitem>
 227           <para>The SELinux security context (label) of the process
 228           the journal entry originates from.</para>
 229         </listitem>
 230       </varlistentry>
 231
 232       <varlistentry>
 233         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 234         <listitem>
 235           <para>The earliest trusted timestamp of the message, if any
 236           is known that is different from the reception time of the
 237           journal. This is the time in microseconds since the epoch
 238           UTC, formatted as a decimal string.</para>
 239         </listitem>
 240       </varlistentry>
 241
 242       <varlistentry>
 243         <term><varname>_BOOT_ID=</varname></term>
 244         <listitem>
 245           <para>The kernel boot ID for the boot the message was
 246           generated in, formatted as a 128-bit hexadecimal
 247           string.</para>
 248         </listitem>
 249       </varlistentry>
 250
 251       <varlistentry>
 252         <term><varname>_MACHINE_ID=</varname></term>
 253         <listitem>
 254           <para>The machine ID of the originating host, as available
 255           in
 256           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 257         </listitem>
 258       </varlistentry>
 259
 260       <varlistentry>
 261         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 262         <listitem>
 263           <para>The invocation ID for the runtime cycle of the unit
 264           the message was generated in, as available to processes
 265           of the unit in <varname>$INVOCATION_ID</varname> (see
 266           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 267         </listitem>
 268       </varlistentry>
 269
 270       <varlistentry>
 271         <term><varname>_HOSTNAME=</varname></term>
 272         <listitem>
 273           <para>The name of the originating host.</para>
 274         </listitem>
 275       </varlistentry>
 276
 277       <varlistentry>
 278         <term><varname>_TRANSPORT=</varname></term>
 279         <listitem>
 280           <para>How the entry was received by the journal service.
 281           Valid transports are:
 282           </para>
 283           <variablelist>
 284             <varlistentry>
 285               <term>
 286                 <option>audit</option>
 287               </term>
 288               <listitem>
 289                 <para>for those read from the kernel audit subsystem
 290                 </para>
 291               </listitem>
 292             </varlistentry>
 293
 294             <varlistentry>
 295               <term>
 296                 <option>driver</option>
 297               </term>
 298               <listitem>
 299                 <para>for internally generated messages
 300                 </para>
 301               </listitem>
 302             </varlistentry>
 303
 304             <varlistentry>
 305               <term>
 306                 <option>syslog</option>
 307               </term>
 308               <listitem>
 309                 <para>for those received via the local syslog socket
 310                 with the syslog protocol
 311                 </para>
 312               </listitem>
 313             </varlistentry>
 314
 315             <varlistentry>
 316               <term>
 317                 <option>journal</option>
 318               </term>
 319               <listitem>
 320                 <para>for those received via the native journal
 321                 protocol
 322                 </para>
 323               </listitem>
 324             </varlistentry>
 325
 326             <varlistentry>
 327               <term>
 328                 <option>stdout</option>
 329               </term>
 330               <listitem>
 331                 <para>for those read from a service's standard output
 332                 or error output
 333                 </para>
 334               </listitem>
 335             </varlistentry>
 336
 337             <varlistentry>
 338               <term>
 339                 <option>kernel</option>
 340               </term>
 341               <listitem>
 342                 <para>for those read from the kernel
 343                 </para>
 344               </listitem>
 345             </varlistentry>
 346           </variablelist>
 347         </listitem>
 348       </varlistentry>
 349       <varlistentry>
 350         <term><varname>_STREAM_ID=</varname></term>
 351         <listitem>
 352           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: specifies a randomized 128bit ID assigned
 353           to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
 354           from the log records: all log records carrying the same stream ID originate from the same stream.</para>
 355         </listitem>
 356       </varlistentry>
 357       <varlistentry>
 358         <term><varname>_LINE_BREAK=</varname></term>
 359         <listitem>
 360           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: indicates that the log message
 361           in the standard output/error stream was not terminated with a normal newline character
 362           (<literal>\n</literal>, i.e. ASCII 10). Specifically, when set this field is one of
 363           <option>nul</option> (in case the line was terminated by a NUL byte), <option>line-max</option> (in
 364           case the maximum log line length was reached, as configured with <varname>LineMax=</varname> in
 365           <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>),
 366           <option>eof</option> (if this was the last log record of a stream and the stream ended without a
 367           final newline character), or <option>pid-change</option> (if the process which generated the log
 368           output changed in the middle of a line). Note that this record is not generated when a normal
 369           newline character was used for marking the log line end.</para>
 370         </listitem>
 371       </varlistentry>
 372       <varlistentry>
 373         <term><varname>_NAMESPACE=</varname></term>
 374
 375         <listitem><para>If this file was written by a <command>systemd-journald</command> instance managing a
 376         journal namespace that is not the default, this field contains the namespace identifier. See
 377         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 378         for details about journal namespaces.</para>
 379         </listitem>
 380       </varlistentry>
 381     </variablelist>
 382   </refsect1>
 383
 384   <refsect1>
 385     <title>Kernel Journal Fields</title>
 386
 387     <para>Kernel fields are fields that are used by messages
 388     originating in the kernel and stored in the journal.</para>
 389
 390     <variablelist class='journal-directives'>
 391       <varlistentry>
 392         <term><varname>_KERNEL_DEVICE=</varname></term>
 393         <listitem>
 394           <para>The kernel device name. If the entry is associated to
 395           a block device, the major and minor of the device node,
 396           separated by <literal>:</literal> and prefixed by
 397           <literal>b</literal>. Similar for character devices but
 398           prefixed by <literal>c</literal>. For network devices, this
 399           is the interface index prefixed by <literal>n</literal>. For
 400           all other devices, this is the subsystem name prefixed by
 401           <literal>+</literal>, followed by <literal>:</literal>,
 402           followed by the kernel device name.</para>
 403         </listitem>
 404       </varlistentry>
 405       <varlistentry>
 406         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 407         <listitem>
 408           <para>The kernel subsystem name.</para>
 409         </listitem>
 410       </varlistentry>
 411       <varlistentry>
 412         <term><varname>_UDEV_SYSNAME=</varname></term>
 413         <listitem>
 414           <para>The kernel device name as it shows up in the device
 415           tree below <filename>/sys</filename>.</para>
 416         </listitem>
 417       </varlistentry>
 418       <varlistentry>
 419         <term><varname>_UDEV_DEVNODE=</varname></term>
 420         <listitem>
 421           <para>The device node path of this device in
 422           <filename>/dev</filename>.</para>
 423         </listitem>
 424       </varlistentry>
 425       <varlistentry>
 426         <term><varname>_UDEV_DEVLINK=</varname></term>
 427         <listitem>
 428           <para>Additional symlink names pointing to the device node
 429           in <filename>/dev</filename>. This field is frequently set
 430           more than once per entry.</para>
 431         </listitem>
 432       </varlistentry>
 433     </variablelist>
 434   </refsect1>
 435
 436   <refsect1>
 437     <title>Fields to log on behalf of a different program</title>
 438
 439     <para>Fields in this section are used by programs to specify that
 440     they are logging on behalf of another program or unit.
 441     </para>
 442
 443     <para>Fields used by the <command>systemd-coredump</command>
 444     coredump kernel helper:
 445     </para>
 446
 447     <variablelist class='journal-directives'>
 448       <varlistentry>
 449         <term><varname>COREDUMP_UNIT=</varname></term>
 450         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 451         <listitem>
 452           <para>Used to annotate messages containing coredumps from
 453           system and session units. See
 454           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 455           </para>
 456         </listitem>
 457       </varlistentry>
 458     </variablelist>
 459
 460     <para>Privileged programs (currently UID 0) may attach
 461     <varname>OBJECT_PID=</varname> to a message. This will instruct
 462     <command>systemd-journald</command> to attach additional fields on
 463     behalf of the caller:</para>
 464
 465     <variablelist class='journal-directives'>
 466       <varlistentry>
 467         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 468         <listitem>
 469           <para>PID of the program that this message pertains to.
 470           </para>
 471         </listitem>
 472       </varlistentry>
 473
 474       <varlistentry>
 475         <term><varname>OBJECT_UID=</varname></term>
 476         <term><varname>OBJECT_GID=</varname></term>
 477         <term><varname>OBJECT_COMM=</varname></term>
 478         <term><varname>OBJECT_EXE=</varname></term>
 479         <term><varname>OBJECT_CMDLINE=</varname></term>
 480         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 481         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 482         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 483         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 484         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 485         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 486         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 487         <listitem>
 488           <para>These are additional fields added automatically by
 489           <command>systemd-journald</command>. Their meaning is the
 490           same as
 491           <varname>_UID=</varname>,
 492           <varname>_GID=</varname>,
 493           <varname>_COMM=</varname>,
 494           <varname>_EXE=</varname>,
 495           <varname>_CMDLINE=</varname>,
 496           <varname>_AUDIT_SESSION=</varname>,
 497           <varname>_AUDIT_LOGINUID=</varname>,
 498           <varname>_SYSTEMD_CGROUP=</varname>,
 499           <varname>_SYSTEMD_SESSION=</varname>,
 500           <varname>_SYSTEMD_UNIT=</varname>,
 501           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 502           <varname>_SYSTEMD_OWNER_UID=</varname>
 503           as described above, except that the process identified by
 504           <replaceable>PID</replaceable> is described, instead of the
 505           process which logged the message.</para>
 506         </listitem>
 507       </varlistentry>
 508     </variablelist>
 509
 510   </refsect1>
 511
 512   <refsect1>
 513     <title>Address Fields</title>
 514
 515     <para>During serialization into external formats, such as the
 516     <ulink
 517     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 518     Export Format</ulink> or the <ulink
 519     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 520     JSON Format</ulink>, the addresses of journal entries are
 521     serialized into fields prefixed with double underscores. Note that
 522     these are not proper fields when stored in the journal but for
 523     addressing metadata of entries. They cannot be written as part of
 524     structured log entries via calls such as
 525     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 526     They may also not be used as matches for
 527     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 528     </para>
 529
 530     <variablelist class='journal-directives'>
 531       <varlistentry>
 532         <term><varname>__CURSOR=</varname></term>
 533         <listitem>
 534           <para>The cursor for the entry. A cursor is an opaque text
 535           string that uniquely describes the position of an entry in
 536           the journal and is portable across machines, platforms and
 537           journal files.
 538           </para>
 539         </listitem>
 540       </varlistentry>
 541
 542       <varlistentry>
 543         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 544         <listitem>
 545           <para>The wallclock time
 546           (<constant>CLOCK_REALTIME</constant>) at the point in time
 547           the entry was received by the journal, in microseconds since
 548           the epoch UTC, formatted as a decimal string. This has
 549           different properties from
 550           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 551           usually a bit later but more likely to be monotonic.
 552           </para>
 553         </listitem>
 554       </varlistentry>
 555
 556       <varlistentry>
 557         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 558         <listitem>
 559           <para>The monotonic time
 560           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 561           the entry was received by the journal in microseconds,
 562           formatted as a decimal string. To be useful as an address
 563           for the entry, this should be combined with the boot ID in
 564           <literal>_BOOT_ID=</literal>.
 565           </para>
 566         </listitem>
 567       </varlistentry>
 568     </variablelist>
 569   </refsect1>
 570
 571   <refsect1>
 572       <title>See Also</title>
 573       <para>
 574         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 575         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 576         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 577         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 578         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 579         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 580         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 581       </para>
 582   </refsect1>
 583
 584 </refentry>