man/systemd.journal-fields.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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   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
 153       <varlistentry>
 154         <term><varname>TID=</varname></term>
 155         <listitem>
 156           <para>The numeric thread ID (TID) the log message originates from.</para>
 157         </listitem>
 158       </varlistentry>
 159     </variablelist>
 160   </refsect1>
 161
 162   <refsect1>
 163     <title>Trusted Journal Fields</title>
 164
 165     <para>Fields prefixed with an underscore are trusted fields, i.e.
 166     fields that are implicitly added by the journal and cannot be
 167     altered by client code.</para>
 168
 169     <variablelist class='journal-directives'>
 170       <varlistentry>
 171         <term><varname>_PID=</varname></term>
 172         <term><varname>_UID=</varname></term>
 173         <term><varname>_GID=</varname></term>
 174         <listitem>
 175           <para>The process, user, and group ID of the process the
 176           journal entry originates from formatted as a decimal
 177           string. Note that entries obtained via <literal>stdout</literal> or
 178           <literal>stderr</literal> of forked processes will contain credentials valid for a parent
 179           process (that initiated the connection to <command>systemd-journald</command>).</para>
 180         </listitem>
 181       </varlistentry>
 182
 183       <varlistentry>
 184         <term><varname>_COMM=</varname></term>
 185         <term><varname>_EXE=</varname></term>
 186         <term><varname>_CMDLINE=</varname></term>
 187         <listitem>
 188           <para>The name, the executable path, and the command line of
 189           the process the journal entry originates from.</para>
 190         </listitem>
 191       </varlistentry>
 192
 193       <varlistentry>
 194         <term><varname>_CAP_EFFECTIVE=</varname></term>
 195         <listitem>
 196           <para>The effective
 197           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 198           of the process the journal entry originates from.</para>
 199         </listitem>
 200       </varlistentry>
 201
 202       <varlistentry>
 203         <term><varname>_AUDIT_SESSION=</varname></term>
 204         <term><varname>_AUDIT_LOGINUID=</varname></term>
 205         <listitem>
 206           <para>The session and login UID of the process the journal
 207           entry originates from, as maintained by the kernel audit
 208           subsystem.</para>
 209         </listitem>
 210       </varlistentry>
 211
 212       <varlistentry>
 213         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 214         <term><varname>_SYSTEMD_SLICE=</varname></term>
 215         <term><varname>_SYSTEMD_UNIT=</varname></term>
 216         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 217         <term><varname>_SYSTEMD_USER_SLICE=</varname></term>
 218         <term><varname>_SYSTEMD_SESSION=</varname></term>
 219         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 220
 221         <listitem>
 222           <para>The control group path in the systemd hierarchy, the systemd slice unit name, the systemd
 223           unit name, the unit name in the systemd user manager (if any), the systemd session ID (if any), and
 224           the owner UID of the systemd user unit or systemd session (if any) of the process the journal entry
 225           originates from.</para>
 226         </listitem>
 227       </varlistentry>
 228
 229       <varlistentry>
 230         <term><varname>_SELINUX_CONTEXT=</varname></term>
 231         <listitem>
 232           <para>The SELinux security context (label) of the process
 233           the journal entry originates from.</para>
 234         </listitem>
 235       </varlistentry>
 236
 237       <varlistentry>
 238         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 239         <listitem>
 240           <para>The earliest trusted timestamp of the message, if any
 241           is known that is different from the reception time of the
 242           journal. This is the time in microseconds since the epoch
 243           UTC, formatted as a decimal string.</para>
 244         </listitem>
 245       </varlistentry>
 246
 247       <varlistentry>
 248         <term><varname>_BOOT_ID=</varname></term>
 249         <listitem>
 250           <para>The kernel boot ID for the boot the message was
 251           generated in, formatted as a 128-bit hexadecimal
 252           string.</para>
 253         </listitem>
 254       </varlistentry>
 255
 256       <varlistentry>
 257         <term><varname>_MACHINE_ID=</varname></term>
 258         <listitem>
 259           <para>The machine ID of the originating host, as available
 260           in
 261           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 262         </listitem>
 263       </varlistentry>
 264
 265       <varlistentry>
 266         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 267         <listitem>
 268           <para>The invocation ID for the runtime cycle of the unit
 269           the message was generated in, as available to processes
 270           of the unit in <varname>$INVOCATION_ID</varname> (see
 271           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 272         </listitem>
 273       </varlistentry>
 274
 275       <varlistentry>
 276         <term><varname>_HOSTNAME=</varname></term>
 277         <listitem>
 278           <para>The name of the originating host.</para>
 279         </listitem>
 280       </varlistentry>
 281
 282       <varlistentry>
 283         <term><varname>_TRANSPORT=</varname></term>
 284         <listitem>
 285           <para>How the entry was received by the journal service.
 286           Valid transports are:
 287           </para>
 288           <variablelist>
 289             <varlistentry>
 290               <term>
 291                 <option>audit</option>
 292               </term>
 293               <listitem>
 294                 <para>for those read from the kernel audit subsystem
 295                 </para>
 296               </listitem>
 297             </varlistentry>
 298
 299             <varlistentry>
 300               <term>
 301                 <option>driver</option>
 302               </term>
 303               <listitem>
 304                 <para>for internally generated messages
 305                 </para>
 306               </listitem>
 307             </varlistentry>
 308
 309             <varlistentry>
 310               <term>
 311                 <option>syslog</option>
 312               </term>
 313               <listitem>
 314                 <para>for those received via the local syslog socket
 315                 with the syslog protocol
 316                 </para>
 317               </listitem>
 318             </varlistentry>
 319
 320             <varlistentry>
 321               <term>
 322                 <option>journal</option>
 323               </term>
 324               <listitem>
 325                 <para>for those received via the native journal
 326                 protocol
 327                 </para>
 328               </listitem>
 329             </varlistentry>
 330
 331             <varlistentry>
 332               <term>
 333                 <option>stdout</option>
 334               </term>
 335               <listitem>
 336                 <para>for those read from a service's standard output
 337                 or error output
 338                 </para>
 339               </listitem>
 340             </varlistentry>
 341
 342             <varlistentry>
 343               <term>
 344                 <option>kernel</option>
 345               </term>
 346               <listitem>
 347                 <para>for those read from the kernel
 348                 </para>
 349               </listitem>
 350             </varlistentry>
 351           </variablelist>
 352         </listitem>
 353       </varlistentry>
 354       <varlistentry>
 355         <term><varname>_STREAM_ID=</varname></term>
 356         <listitem>
 357           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: specifies a randomized 128bit ID assigned
 358           to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
 359           from the log records: all log records carrying the same stream ID originate from the same stream.</para>
 360         </listitem>
 361       </varlistentry>
 362       <varlistentry>
 363         <term><varname>_LINE_BREAK=</varname></term>
 364         <listitem>
 365           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: indicates that the log message
 366           in the standard output/error stream was not terminated with a normal newline character
 367           (<literal>\n</literal>, i.e. ASCII 10). Specifically, when set this field is one of
 368           <option>nul</option> (in case the line was terminated by a NUL byte), <option>line-max</option> (in
 369           case the maximum log line length was reached, as configured with <varname>LineMax=</varname> in
 370           <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>),
 371           <option>eof</option> (if this was the last log record of a stream and the stream ended without a
 372           final newline character), or <option>pid-change</option> (if the process which generated the log
 373           output changed in the middle of a line). Note that this record is not generated when a normal
 374           newline character was used for marking the log line end.</para>
 375         </listitem>
 376       </varlistentry>
 377       <varlistentry>
 378         <term><varname>_NAMESPACE=</varname></term>
 379
 380         <listitem><para>If this file was written by a <command>systemd-journald</command> instance managing a
 381         journal namespace that is not the default, this field contains the namespace identifier. See
 382         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 383         for details about journal namespaces.</para>
 384         </listitem>
 385       </varlistentry>
 386     </variablelist>
 387   </refsect1>
 388
 389   <refsect1>
 390     <title>Kernel Journal Fields</title>
 391
 392     <para>Kernel fields are fields that are used by messages
 393     originating in the kernel and stored in the journal.</para>
 394
 395     <variablelist class='journal-directives'>
 396       <varlistentry>
 397         <term><varname>_KERNEL_DEVICE=</varname></term>
 398         <listitem>
 399           <para>The kernel device name. If the entry is associated to a block device, contains the major and
 400           minor numbers of the device node, separated by <literal>:</literal> and prefixed by
 401           <literal>b</literal>. Similarly for character devices, but prefixed by <literal>c</literal>. For
 402           network devices, this is the interface index prefixed by <literal>n</literal>. For all other
 403           devices, this is the subsystem name prefixed by <literal>+</literal>, followed by
 404           <literal>:</literal>, followed by the kernel device name.</para>
 405         </listitem>
 406       </varlistentry>
 407       <varlistentry>
 408         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 409         <listitem>
 410           <para>The kernel subsystem name.</para>
 411         </listitem>
 412       </varlistentry>
 413       <varlistentry>
 414         <term><varname>_UDEV_SYSNAME=</varname></term>
 415         <listitem>
 416           <para>The kernel device name as it shows up in the device
 417           tree below <filename>/sys/</filename>.</para>
 418         </listitem>
 419       </varlistentry>
 420       <varlistentry>
 421         <term><varname>_UDEV_DEVNODE=</varname></term>
 422         <listitem>
 423           <para>The device node path of this device in
 424           <filename>/dev/</filename>.</para>
 425         </listitem>
 426       </varlistentry>
 427       <varlistentry>
 428         <term><varname>_UDEV_DEVLINK=</varname></term>
 429         <listitem>
 430           <para>Additional symlink names pointing to the device node
 431           in <filename>/dev/</filename>. This field is frequently set
 432           more than once per entry.</para>
 433         </listitem>
 434       </varlistentry>
 435     </variablelist>
 436   </refsect1>
 437
 438   <refsect1>
 439     <title>Fields to log on behalf of a different program</title>
 440
 441     <para>Fields in this section are used by programs to specify that
 442     they are logging on behalf of another program or unit.
 443     </para>
 444
 445     <para>Fields used by the <command>systemd-coredump</command>
 446     coredump kernel helper:
 447     </para>
 448
 449     <variablelist class='journal-directives'>
 450       <varlistentry>
 451         <term><varname>COREDUMP_UNIT=</varname></term>
 452         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 453         <listitem>
 454           <para>Used to annotate messages containing coredumps from
 455           system and session units. See
 456           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 457           </para>
 458         </listitem>
 459       </varlistentry>
 460     </variablelist>
 461
 462     <para>Privileged programs (currently UID 0) may attach
 463     <varname>OBJECT_PID=</varname> to a message. This will instruct
 464     <command>systemd-journald</command> to attach additional fields on
 465     behalf of the caller:</para>
 466
 467     <variablelist class='journal-directives'>
 468       <varlistentry>
 469         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 470         <listitem>
 471           <para>PID of the program that this message pertains to.
 472           </para>
 473         </listitem>
 474       </varlistentry>
 475
 476       <varlistentry>
 477         <term><varname>OBJECT_UID=</varname></term>
 478         <term><varname>OBJECT_GID=</varname></term>
 479         <term><varname>OBJECT_COMM=</varname></term>
 480         <term><varname>OBJECT_EXE=</varname></term>
 481         <term><varname>OBJECT_CMDLINE=</varname></term>
 482         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 483         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 484         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 485         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 486         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 487         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 488         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 489         <listitem>
 490           <para>These are additional fields added automatically by
 491           <command>systemd-journald</command>. Their meaning is the
 492           same as
 493           <varname>_UID=</varname>,
 494           <varname>_GID=</varname>,
 495           <varname>_COMM=</varname>,
 496           <varname>_EXE=</varname>,
 497           <varname>_CMDLINE=</varname>,
 498           <varname>_AUDIT_SESSION=</varname>,
 499           <varname>_AUDIT_LOGINUID=</varname>,
 500           <varname>_SYSTEMD_CGROUP=</varname>,
 501           <varname>_SYSTEMD_SESSION=</varname>,
 502           <varname>_SYSTEMD_UNIT=</varname>,
 503           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 504           <varname>_SYSTEMD_OWNER_UID=</varname>
 505           as described above, except that the process identified by
 506           <replaceable>PID</replaceable> is described, instead of the
 507           process which logged the message.</para>
 508         </listitem>
 509       </varlistentry>
 510     </variablelist>
 511
 512   </refsect1>
 513
 514   <refsect1>
 515     <title>Address Fields</title>
 516
 517     <para>During serialization into external formats, such as the
 518     <ulink
 519     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 520     Export Format</ulink> or the <ulink
 521     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 522     JSON Format</ulink>, the addresses of journal entries are
 523     serialized into fields prefixed with double underscores. Note that
 524     these are not proper fields when stored in the journal but for
 525     addressing metadata of entries. They cannot be written as part of
 526     structured log entries via calls such as
 527     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 528     They may also not be used as matches for
 529     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 530     </para>
 531
 532     <variablelist class='journal-directives'>
 533       <varlistentry>
 534         <term><varname>__CURSOR=</varname></term>
 535         <listitem>
 536           <para>The cursor for the entry. A cursor is an opaque text
 537           string that uniquely describes the position of an entry in
 538           the journal and is portable across machines, platforms and
 539           journal files.
 540           </para>
 541         </listitem>
 542       </varlistentry>
 543
 544       <varlistentry>
 545         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 546         <listitem>
 547           <para>The wallclock time
 548           (<constant>CLOCK_REALTIME</constant>) at the point in time
 549           the entry was received by the journal, in microseconds since
 550           the epoch UTC, formatted as a decimal string. This has
 551           different properties from
 552           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 553           usually a bit later but more likely to be monotonic.
 554           </para>
 555         </listitem>
 556       </varlistentry>
 557
 558       <varlistentry>
 559         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 560         <listitem>
 561           <para>The monotonic time
 562           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 563           the entry was received by the journal in microseconds,
 564           formatted as a decimal string. To be useful as an address
 565           for the entry, this should be combined with the boot ID in
 566           <literal>_BOOT_ID=</literal>.
 567           </para>
 568         </listitem>
 569       </varlistentry>
 570     </variablelist>
 571   </refsect1>
 572
 573   <refsect1>
 574       <title>See Also</title>
 575       <para>
 576         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 577         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 578         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 579         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 580         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 581         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 582         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 583       </para>
 584   </refsect1>
 585
 586 </refentry>