man/systemd.journal-fields.xml

   1 <?xml version='1.0'?> <!--*-nxml-*-->
   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2010 Lennart Poettering
  11 -->
  12
  13 <refentry id="systemd.journal-fields">
  14
  15   <refentryinfo>
  16     <title>systemd.journal-fields</title>
  17     <productname>systemd</productname>
  18
  19     <authorgroup>
  20       <author>
  21         <contrib>Developer</contrib>
  22         <firstname>Lennart</firstname>
  23         <surname>Poettering</surname>
  24         <email>lennart@poettering.net</email>
  25       </author>
  26     </authorgroup>
  27   </refentryinfo>
  28
  29   <refmeta>
  30     <refentrytitle>systemd.journal-fields</refentrytitle>
  31     <manvolnum>7</manvolnum>
  32   </refmeta>
  33
  34   <refnamediv>
  35     <refname>systemd.journal-fields</refname>
  36     <refpurpose>Special journal fields</refpurpose>
  37   </refnamediv>
  38
  39   <refsect1>
  40     <title>Description</title>
  41
  42     <para>Entries in the journal resemble an environment block in
  43     their syntax but with fields that can include binary data.
  44     Primarily, fields are formatted UTF-8 text strings, and binary
  45     formatting is used only where formatting as UTF-8 text strings
  46     makes little sense. New fields may freely be defined by
  47     applications, but a few fields have special meaning. All fields
  48     with special meanings are optional. In some cases, fields may
  49     appear more than once per entry.</para>
  50   </refsect1>
  51
  52   <refsect1>
  53     <title>User Journal Fields</title>
  54
  55     <para>User fields are fields that are directly passed from clients
  56     and stored in the journal.</para>
  57
  58     <variablelist class='journal-directives'>
  59       <varlistentry>
  60         <term><varname>MESSAGE=</varname></term>
  61         <listitem>
  62           <para>The human-readable message string for this entry. This
  63           is supposed to be the primary text shown to the user. It is
  64           usually not translated (but might be in some cases), and is
  65           not supposed to be parsed for metadata.</para>
  66         </listitem>
  67       </varlistentry>
  68
  69       <varlistentry>
  70         <term><varname>MESSAGE_ID=</varname></term>
  71         <listitem>
  72           <para>A 128-bit message identifier ID for recognizing
  73           certain message types, if this is desirable. This should
  74           contain a 128-bit ID formatted as a lower-case hexadecimal
  75           string, without any separating dashes or suchlike. This is
  76           recommended to be a UUID-compatible ID, but this is not
  77           enforced, and formatted differently. Developers can generate
  78           a new ID for this purpose with <command>journalctl
  79           <option>--new-id128</option></command>.
  80           </para>
  81         </listitem>
  82       </varlistentry>
  83
  84       <varlistentry>
  85         <term><varname>PRIORITY=</varname></term>
  86         <listitem>
  87           <para>A priority value between 0 (<literal>emerg</literal>)
  88           and 7 (<literal>debug</literal>) formatted as a decimal
  89           string. This field is compatible with syslog's priority
  90           concept.</para>
  91         </listitem>
  92       </varlistentry>
  93
  94       <varlistentry>
  95         <term><varname>CODE_FILE=</varname></term>
  96         <term><varname>CODE_LINE=</varname></term>
  97         <term><varname>CODE_FUNC=</varname></term>
  98         <listitem>
  99           <para>The code location generating this message, if known.
 100           Contains the source filename, the line number and the
 101           function name.</para>
 102         </listitem>
 103       </varlistentry>
 104
 105       <varlistentry>
 106         <term><varname>ERRNO=</varname></term>
 107         <listitem>
 108           <para>The low-level Unix error number causing this entry, if
 109           any. Contains the numeric value of
 110           <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 111           formatted as a decimal string.</para>
 112         </listitem>
 113       </varlistentry>
 114
 115       <varlistentry>
 116         <term><varname>SYSLOG_FACILITY=</varname></term>
 117         <term><varname>SYSLOG_IDENTIFIER=</varname></term>
 118         <term><varname>SYSLOG_PID=</varname></term>
 119         <listitem>
 120           <para>Syslog compatibility fields containing the facility
 121           (formatted as decimal string), the identifier string (i.e.
 122           "tag"), and the client PID. (Note that the tag is usually
 123           derived from glibc's
 124           <varname>program_invocation_short_name</varname> variable,
 125           see
 126           <citerefentry project='die-net'><refentrytitle>program_invocation_short_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.)</para>
 127         </listitem>
 128
 129       </varlistentry>
 130     </variablelist>
 131   </refsect1>
 132
 133   <refsect1>
 134     <title>Trusted Journal Fields</title>
 135
 136     <para>Fields prefixed with an underscore are trusted fields, i.e.
 137     fields that are implicitly added by the journal and cannot be
 138     altered by client code.</para>
 139
 140     <variablelist class='journal-directives'>
 141       <varlistentry>
 142         <term><varname>_PID=</varname></term>
 143         <term><varname>_UID=</varname></term>
 144         <term><varname>_GID=</varname></term>
 145         <listitem>
 146           <para>The process, user, and group ID of the process the
 147           journal entry originates from formatted as a decimal
 148           string. Note that entries obtained via <literal>stdout</literal> or
 149           <literal>stderr</literal> of forked processes will contain credentials valid for a parent
 150           process (that initiated the connection to <command>systemd-journald</command>).</para>
 151         </listitem>
 152       </varlistentry>
 153
 154       <varlistentry>
 155         <term><varname>_COMM=</varname></term>
 156         <term><varname>_EXE=</varname></term>
 157         <term><varname>_CMDLINE=</varname></term>
 158         <listitem>
 159           <para>The name, the executable path, and the command line of
 160           the process the journal entry originates from.</para>
 161         </listitem>
 162       </varlistentry>
 163
 164       <varlistentry>
 165         <term><varname>_CAP_EFFECTIVE=</varname></term>
 166         <listitem>
 167           <para>The effective
 168           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 169           of the process the journal entry originates from.</para>
 170         </listitem>
 171       </varlistentry>
 172
 173       <varlistentry>
 174         <term><varname>_AUDIT_SESSION=</varname></term>
 175         <term><varname>_AUDIT_LOGINUID=</varname></term>
 176         <listitem>
 177           <para>The session and login UID of the process the journal
 178           entry originates from, as maintained by the kernel audit
 179           subsystem.</para>
 180         </listitem>
 181       </varlistentry>
 182
 183       <varlistentry>
 184         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 185         <term><varname>_SYSTEMD_SLICE=</varname></term>
 186         <term><varname>_SYSTEMD_UNIT=</varname></term>
 187         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 188         <term><varname>_SYSTEMD_SESSION=</varname></term>
 189         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 190
 191         <listitem>
 192           <para>The control group path in the systemd hierarchy, the
 193           the systemd slice unit name, the systemd unit name, the
 194           unit name in the systemd user manager (if any), the systemd
 195           session ID (if any), and the owner UID of the systemd user
 196           unit or systemd session (if any) of the process the journal
 197           entry originates from.</para>
 198         </listitem>
 199       </varlistentry>
 200
 201       <varlistentry>
 202         <term><varname>_SELINUX_CONTEXT=</varname></term>
 203         <listitem>
 204           <para>The SELinux security context (label) of the process
 205           the journal entry originates from.</para>
 206         </listitem>
 207       </varlistentry>
 208
 209       <varlistentry>
 210         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 211         <listitem>
 212           <para>The earliest trusted timestamp of the message, if any
 213           is known that is different from the reception time of the
 214           journal. This is the time in microseconds since the epoch
 215           UTC, formatted as a decimal string.</para>
 216         </listitem>
 217       </varlistentry>
 218
 219       <varlistentry>
 220         <term><varname>_BOOT_ID=</varname></term>
 221         <listitem>
 222           <para>The kernel boot ID for the boot the message was
 223           generated in, formatted as a 128-bit hexadecimal
 224           string.</para>
 225         </listitem>
 226       </varlistentry>
 227
 228       <varlistentry>
 229         <term><varname>_MACHINE_ID=</varname></term>
 230         <listitem>
 231           <para>The machine ID of the originating host, as available
 232           in
 233           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 234         </listitem>
 235       </varlistentry>
 236
 237       <varlistentry>
 238         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 239         <listitem>
 240           <para>The invocation ID for the runtime cycle of the unit
 241           the message was generated in, as available to processes
 242           of the unit in <varname>$INVOCATION_ID</varname> (see
 243           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 244         </listitem>
 245       </varlistentry>
 246
 247       <varlistentry>
 248         <term><varname>_HOSTNAME=</varname></term>
 249         <listitem>
 250           <para>The name of the originating host.</para>
 251         </listitem>
 252       </varlistentry>
 253
 254       <varlistentry>
 255         <term><varname>_TRANSPORT=</varname></term>
 256         <listitem>
 257           <para>How the entry was received by the journal service.
 258           Valid transports are:
 259           </para>
 260           <variablelist>
 261             <varlistentry>
 262               <term>
 263                 <option>audit</option>
 264               </term>
 265               <listitem>
 266                 <para>for those read from the kernel audit subsystem
 267                 </para>
 268               </listitem>
 269             </varlistentry>
 270
 271             <varlistentry>
 272               <term>
 273                 <option>driver</option>
 274               </term>
 275               <listitem>
 276                 <para>for internally generated messages
 277                 </para>
 278               </listitem>
 279             </varlistentry>
 280
 281             <varlistentry>
 282               <term>
 283                 <option>syslog</option>
 284               </term>
 285               <listitem>
 286                 <para>for those received via the local syslog socket
 287                 with the syslog protocol
 288                 </para>
 289               </listitem>
 290             </varlistentry>
 291
 292             <varlistentry>
 293               <term>
 294                 <option>journal</option>
 295               </term>
 296               <listitem>
 297                 <para>for those received via the native journal
 298                 protocol
 299                 </para>
 300               </listitem>
 301             </varlistentry>
 302
 303             <varlistentry>
 304               <term>
 305                 <option>stdout</option>
 306               </term>
 307               <listitem>
 308                 <para>for those read from a service's standard output
 309                 or error output
 310                 </para>
 311               </listitem>
 312             </varlistentry>
 313
 314             <varlistentry>
 315               <term>
 316                 <option>kernel</option>
 317               </term>
 318               <listitem>
 319                 <para>for those read from the kernel
 320                 </para>
 321               </listitem>
 322             </varlistentry>
 323           </variablelist>
 324         </listitem>
 325       </varlistentry>
 326       <varlistentry>
 327         <term><varname>_STREAM_ID=</varname></term>
 328         <listitem>
 329           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: specifies a randomized 128bit ID assigned
 330           to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
 331           from the log records: all log records carrying the same stream ID originate from the same stream.</para>
 332         </listitem>
 333       </varlistentry>
 334       <varlistentry>
 335         <term><varname>_LINE_BREAK=</varname></term>
 336         <listitem>
 337           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: indicates that the log message in the
 338           standard output/error stream was not terminated with a normal newline character (<literal>\n</literal>,
 339           i.e. ASCII 10). Specifically, when set this field is one of <option>nul</option> (in case the line was
 340           terminated by a NUL byte), <option>line-max</option> (in case the maximum log line length was reached, as
 341           configured with <varname>LineMax=</varname> in
 342           <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or
 343           <option>eof</option> (if this was the last log record of a stream and the stream ended without a final
 344           newline character). Note that this record is not generated when a normal newline character was used for
 345           marking the log line end.</para>
 346         </listitem>
 347       </varlistentry>
 348     </variablelist>
 349   </refsect1>
 350
 351   <refsect1>
 352     <title>Kernel Journal Fields</title>
 353
 354     <para>Kernel fields are fields that are used by messages
 355     originating in the kernel and stored in the journal.</para>
 356
 357     <variablelist class='journal-directives'>
 358       <varlistentry>
 359         <term><varname>_KERNEL_DEVICE=</varname></term>
 360         <listitem>
 361           <para>The kernel device name. If the entry is associated to
 362           a block device, the major and minor of the device node,
 363           separated by <literal>:</literal> and prefixed by
 364           <literal>b</literal>. Similar for character devices but
 365           prefixed by <literal>c</literal>. For network devices, this
 366           is the interface index prefixed by <literal>n</literal>. For
 367           all other devices, this is the subsystem name prefixed by
 368           <literal>+</literal>, followed by <literal>:</literal>,
 369           followed by the kernel device name.</para>
 370         </listitem>
 371       </varlistentry>
 372       <varlistentry>
 373         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 374         <listitem>
 375           <para>The kernel subsystem name.</para>
 376         </listitem>
 377       </varlistentry>
 378       <varlistentry>
 379         <term><varname>_UDEV_SYSNAME=</varname></term>
 380         <listitem>
 381           <para>The kernel device name as it shows up in the device
 382           tree below <filename>/sys</filename>.</para>
 383         </listitem>
 384       </varlistentry>
 385       <varlistentry>
 386         <term><varname>_UDEV_DEVNODE=</varname></term>
 387         <listitem>
 388           <para>The device node path of this device in
 389           <filename>/dev</filename>.</para>
 390         </listitem>
 391       </varlistentry>
 392       <varlistentry>
 393         <term><varname>_UDEV_DEVLINK=</varname></term>
 394         <listitem>
 395           <para>Additional symlink names pointing to the device node
 396           in <filename>/dev</filename>. This field is frequently set
 397           more than once per entry.</para>
 398         </listitem>
 399       </varlistentry>
 400     </variablelist>
 401   </refsect1>
 402
 403   <refsect1>
 404     <title>Fields to log on behalf of a different program</title>
 405
 406     <para>Fields in this section are used by programs to specify that
 407     they are logging on behalf of another program or unit.
 408     </para>
 409
 410     <para>Fields used by the <command>systemd-coredump</command>
 411     coredump kernel helper:
 412     </para>
 413
 414     <variablelist class='journal-directives'>
 415       <varlistentry>
 416         <term><varname>COREDUMP_UNIT=</varname></term>
 417         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 418         <listitem>
 419           <para>Used to annotate messages containing coredumps from
 420           system and session units. See
 421           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 422           </para>
 423         </listitem>
 424       </varlistentry>
 425     </variablelist>
 426
 427     <para>Privileged programs (currently UID 0) may attach
 428     <varname>OBJECT_PID=</varname> to a message. This will instruct
 429     <command>systemd-journald</command> to attach additional fields on
 430     behalf of the caller:</para>
 431
 432     <variablelist class='journal-directives'>
 433       <varlistentry>
 434         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 435         <listitem>
 436           <para>PID of the program that this message pertains to.
 437           </para>
 438         </listitem>
 439       </varlistentry>
 440
 441       <varlistentry>
 442         <term><varname>OBJECT_UID=</varname></term>
 443         <term><varname>OBJECT_GID=</varname></term>
 444         <term><varname>OBJECT_COMM=</varname></term>
 445         <term><varname>OBJECT_EXE=</varname></term>
 446         <term><varname>OBJECT_CMDLINE=</varname></term>
 447         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 448         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 449         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 450         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 451         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 452         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 453         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 454         <listitem>
 455           <para>These are additional fields added automatically by
 456           <command>systemd-journald</command>. Their meaning is the
 457           same as
 458           <varname>_UID=</varname>,
 459           <varname>_GID=</varname>,
 460           <varname>_COMM=</varname>,
 461           <varname>_EXE=</varname>,
 462           <varname>_CMDLINE=</varname>,
 463           <varname>_AUDIT_SESSION=</varname>,
 464           <varname>_AUDIT_LOGINUID=</varname>,
 465           <varname>_SYSTEMD_CGROUP=</varname>,
 466           <varname>_SYSTEMD_SESSION=</varname>,
 467           <varname>_SYSTEMD_UNIT=</varname>,
 468           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 469           <varname>_SYSTEMD_OWNER_UID=</varname>
 470           as described above, except that the process identified by
 471           <replaceable>PID</replaceable> is described, instead of the
 472           process which logged the message.</para>
 473         </listitem>
 474       </varlistentry>
 475     </variablelist>
 476
 477   </refsect1>
 478
 479   <refsect1>
 480     <title>Address Fields</title>
 481
 482     <para>During serialization into external formats, such as the
 483     <ulink
 484     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 485     Export Format</ulink> or the <ulink
 486     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 487     JSON Format</ulink>, the addresses of journal entries are
 488     serialized into fields prefixed with double underscores. Note that
 489     these are not proper fields when stored in the journal but for
 490     addressing metadata of entries. They cannot be written as part of
 491     structured log entries via calls such as
 492     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 493     They may also not be used as matches for
 494     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
 495
 496     <variablelist class='journal-directives'>
 497       <varlistentry>
 498         <term><varname>__CURSOR=</varname></term>
 499         <listitem>
 500           <para>The cursor for the entry. A cursor is an opaque text
 501           string that uniquely describes the position of an entry in
 502           the journal and is portable across machines, platforms and
 503           journal files.
 504           </para>
 505         </listitem>
 506       </varlistentry>
 507
 508       <varlistentry>
 509         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 510         <listitem>
 511           <para>The wallclock time
 512           (<constant>CLOCK_REALTIME</constant>) at the point in time
 513           the entry was received by the journal, in microseconds since
 514           the epoch UTC, formatted as a decimal string. This has
 515           different properties from
 516           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 517           usually a bit later but more likely to be monotonic.
 518           </para>
 519         </listitem>
 520       </varlistentry>
 521
 522       <varlistentry>
 523         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 524         <listitem>
 525           <para>The monotonic time
 526           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 527           the entry was received by the journal in microseconds,
 528           formatted as a decimal string. To be useful as an address
 529           for the entry, this should be combined with the boot ID in
 530           <literal>_BOOT_ID=</literal>.
 531           </para>
 532         </listitem>
 533       </varlistentry>
 534     </variablelist>
 535   </refsect1>
 536
 537   <refsect1>
 538       <title>See Also</title>
 539       <para>
 540         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 541         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 542         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 543         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 544         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 545         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 546       </para>
 547   </refsect1>
 548
 549 </refentry>