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     </variablelist>
 143   </refsect1>
 144
 145   <refsect1>
 146     <title>Trusted Journal Fields</title>
 147
 148     <para>Fields prefixed with an underscore are trusted fields, i.e.
 149     fields that are implicitly added by the journal and cannot be
 150     altered by client code.</para>
 151
 152     <variablelist class='journal-directives'>
 153       <varlistentry>
 154         <term><varname>_PID=</varname></term>
 155         <term><varname>_UID=</varname></term>
 156         <term><varname>_GID=</varname></term>
 157         <listitem>
 158           <para>The process, user, and group ID of the process the
 159           journal entry originates from formatted as a decimal
 160           string. Note that entries obtained via <literal>stdout</literal> or
 161           <literal>stderr</literal> of forked processes will contain credentials valid for a parent
 162           process (that initiated the connection to <command>systemd-journald</command>).</para>
 163         </listitem>
 164       </varlistentry>
 165
 166       <varlistentry>
 167         <term><varname>_COMM=</varname></term>
 168         <term><varname>_EXE=</varname></term>
 169         <term><varname>_CMDLINE=</varname></term>
 170         <listitem>
 171           <para>The name, the executable path, and the command line of
 172           the process the journal entry originates from.</para>
 173         </listitem>
 174       </varlistentry>
 175
 176       <varlistentry>
 177         <term><varname>_CAP_EFFECTIVE=</varname></term>
 178         <listitem>
 179           <para>The effective
 180           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 181           of the process the journal entry originates from.</para>
 182         </listitem>
 183       </varlistentry>
 184
 185       <varlistentry>
 186         <term><varname>_AUDIT_SESSION=</varname></term>
 187         <term><varname>_AUDIT_LOGINUID=</varname></term>
 188         <listitem>
 189           <para>The session and login UID of the process the journal
 190           entry originates from, as maintained by the kernel audit
 191           subsystem.</para>
 192         </listitem>
 193       </varlistentry>
 194
 195       <varlistentry>
 196         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 197         <term><varname>_SYSTEMD_SLICE=</varname></term>
 198         <term><varname>_SYSTEMD_UNIT=</varname></term>
 199         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 200         <term><varname>_SYSTEMD_USER_SLICE=</varname></term>
 201         <term><varname>_SYSTEMD_SESSION=</varname></term>
 202         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 203
 204         <listitem>
 205           <para>The control group path in the systemd hierarchy, the
 206           the systemd slice unit name, the systemd unit name, the
 207           unit name in the systemd user manager (if any), the systemd
 208           session ID (if any), and the owner UID of the systemd user
 209           unit or systemd session (if any) of the process the journal
 210           entry originates from.</para>
 211         </listitem>
 212       </varlistentry>
 213
 214       <varlistentry>
 215         <term><varname>_SELINUX_CONTEXT=</varname></term>
 216         <listitem>
 217           <para>The SELinux security context (label) of the process
 218           the journal entry originates from.</para>
 219         </listitem>
 220       </varlistentry>
 221
 222       <varlistentry>
 223         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 224         <listitem>
 225           <para>The earliest trusted timestamp of the message, if any
 226           is known that is different from the reception time of the
 227           journal. This is the time in microseconds since the epoch
 228           UTC, formatted as a decimal string.</para>
 229         </listitem>
 230       </varlistentry>
 231
 232       <varlistentry>
 233         <term><varname>_BOOT_ID=</varname></term>
 234         <listitem>
 235           <para>The kernel boot ID for the boot the message was
 236           generated in, formatted as a 128-bit hexadecimal
 237           string.</para>
 238         </listitem>
 239       </varlistentry>
 240
 241       <varlistentry>
 242         <term><varname>_MACHINE_ID=</varname></term>
 243         <listitem>
 244           <para>The machine ID of the originating host, as available
 245           in
 246           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 247         </listitem>
 248       </varlistentry>
 249
 250       <varlistentry>
 251         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 252         <listitem>
 253           <para>The invocation ID for the runtime cycle of the unit
 254           the message was generated in, as available to processes
 255           of the unit in <varname>$INVOCATION_ID</varname> (see
 256           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 257         </listitem>
 258       </varlistentry>
 259
 260       <varlistentry>
 261         <term><varname>_HOSTNAME=</varname></term>
 262         <listitem>
 263           <para>The name of the originating host.</para>
 264         </listitem>
 265       </varlistentry>
 266
 267       <varlistentry>
 268         <term><varname>_TRANSPORT=</varname></term>
 269         <listitem>
 270           <para>How the entry was received by the journal service.
 271           Valid transports are:
 272           </para>
 273           <variablelist>
 274             <varlistentry>
 275               <term>
 276                 <option>audit</option>
 277               </term>
 278               <listitem>
 279                 <para>for those read from the kernel audit subsystem
 280                 </para>
 281               </listitem>
 282             </varlistentry>
 283
 284             <varlistentry>
 285               <term>
 286                 <option>driver</option>
 287               </term>
 288               <listitem>
 289                 <para>for internally generated messages
 290                 </para>
 291               </listitem>
 292             </varlistentry>
 293
 294             <varlistentry>
 295               <term>
 296                 <option>syslog</option>
 297               </term>
 298               <listitem>
 299                 <para>for those received via the local syslog socket
 300                 with the syslog protocol
 301                 </para>
 302               </listitem>
 303             </varlistentry>
 304
 305             <varlistentry>
 306               <term>
 307                 <option>journal</option>
 308               </term>
 309               <listitem>
 310                 <para>for those received via the native journal
 311                 protocol
 312                 </para>
 313               </listitem>
 314             </varlistentry>
 315
 316             <varlistentry>
 317               <term>
 318                 <option>stdout</option>
 319               </term>
 320               <listitem>
 321                 <para>for those read from a service's standard output
 322                 or error output
 323                 </para>
 324               </listitem>
 325             </varlistentry>
 326
 327             <varlistentry>
 328               <term>
 329                 <option>kernel</option>
 330               </term>
 331               <listitem>
 332                 <para>for those read from the kernel
 333                 </para>
 334               </listitem>
 335             </varlistentry>
 336           </variablelist>
 337         </listitem>
 338       </varlistentry>
 339       <varlistentry>
 340         <term><varname>_STREAM_ID=</varname></term>
 341         <listitem>
 342           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: specifies a randomized 128bit ID assigned
 343           to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
 344           from the log records: all log records carrying the same stream ID originate from the same stream.</para>
 345         </listitem>
 346       </varlistentry>
 347       <varlistentry>
 348         <term><varname>_LINE_BREAK=</varname></term>
 349         <listitem>
 350           <para>Only applies to <literal>_TRANSPORT=stdout</literal> records: indicates that the log message in the
 351           standard output/error stream was not terminated with a normal newline character (<literal>\n</literal>,
 352           i.e. ASCII 10). Specifically, when set this field is one of <option>nul</option> (in case the line was
 353           terminated by a NUL byte), <option>line-max</option> (in case the maximum log line length was reached, as
 354           configured with <varname>LineMax=</varname> in
 355           <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or
 356           <option>eof</option> (if this was the last log record of a stream and the stream ended without a final
 357           newline character). Note that this record is not generated when a normal newline character was used for
 358           marking the log line end.</para>
 359         </listitem>
 360       </varlistentry>
 361       <varlistentry>
 362         <term><varname>_NAMESPACE=</varname></term>
 363
 364         <listitem><para>If this file was written by a <command>systemd-journald</command> instance managing a
 365         journal namespace that is not the default, this field contains the namespace identifier. See
 366         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
 367         for details about journal namespaces.</para>
 368         </listitem>
 369       </varlistentry>
 370     </variablelist>
 371   </refsect1>
 372
 373   <refsect1>
 374     <title>Kernel Journal Fields</title>
 375
 376     <para>Kernel fields are fields that are used by messages
 377     originating in the kernel and stored in the journal.</para>
 378
 379     <variablelist class='journal-directives'>
 380       <varlistentry>
 381         <term><varname>_KERNEL_DEVICE=</varname></term>
 382         <listitem>
 383           <para>The kernel device name. If the entry is associated to
 384           a block device, the major and minor of the device node,
 385           separated by <literal>:</literal> and prefixed by
 386           <literal>b</literal>. Similar for character devices but
 387           prefixed by <literal>c</literal>. For network devices, this
 388           is the interface index prefixed by <literal>n</literal>. For
 389           all other devices, this is the subsystem name prefixed by
 390           <literal>+</literal>, followed by <literal>:</literal>,
 391           followed by the kernel device name.</para>
 392         </listitem>
 393       </varlistentry>
 394       <varlistentry>
 395         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 396         <listitem>
 397           <para>The kernel subsystem name.</para>
 398         </listitem>
 399       </varlistentry>
 400       <varlistentry>
 401         <term><varname>_UDEV_SYSNAME=</varname></term>
 402         <listitem>
 403           <para>The kernel device name as it shows up in the device
 404           tree below <filename>/sys</filename>.</para>
 405         </listitem>
 406       </varlistentry>
 407       <varlistentry>
 408         <term><varname>_UDEV_DEVNODE=</varname></term>
 409         <listitem>
 410           <para>The device node path of this device in
 411           <filename>/dev</filename>.</para>
 412         </listitem>
 413       </varlistentry>
 414       <varlistentry>
 415         <term><varname>_UDEV_DEVLINK=</varname></term>
 416         <listitem>
 417           <para>Additional symlink names pointing to the device node
 418           in <filename>/dev</filename>. This field is frequently set
 419           more than once per entry.</para>
 420         </listitem>
 421       </varlistentry>
 422     </variablelist>
 423   </refsect1>
 424
 425   <refsect1>
 426     <title>Fields to log on behalf of a different program</title>
 427
 428     <para>Fields in this section are used by programs to specify that
 429     they are logging on behalf of another program or unit.
 430     </para>
 431
 432     <para>Fields used by the <command>systemd-coredump</command>
 433     coredump kernel helper:
 434     </para>
 435
 436     <variablelist class='journal-directives'>
 437       <varlistentry>
 438         <term><varname>COREDUMP_UNIT=</varname></term>
 439         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 440         <listitem>
 441           <para>Used to annotate messages containing coredumps from
 442           system and session units. See
 443           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 444           </para>
 445         </listitem>
 446       </varlistentry>
 447     </variablelist>
 448
 449     <para>Privileged programs (currently UID 0) may attach
 450     <varname>OBJECT_PID=</varname> to a message. This will instruct
 451     <command>systemd-journald</command> to attach additional fields on
 452     behalf of the caller:</para>
 453
 454     <variablelist class='journal-directives'>
 455       <varlistentry>
 456         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 457         <listitem>
 458           <para>PID of the program that this message pertains to.
 459           </para>
 460         </listitem>
 461       </varlistentry>
 462
 463       <varlistentry>
 464         <term><varname>OBJECT_UID=</varname></term>
 465         <term><varname>OBJECT_GID=</varname></term>
 466         <term><varname>OBJECT_COMM=</varname></term>
 467         <term><varname>OBJECT_EXE=</varname></term>
 468         <term><varname>OBJECT_CMDLINE=</varname></term>
 469         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 470         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 471         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 472         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 473         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 474         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 475         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 476         <listitem>
 477           <para>These are additional fields added automatically by
 478           <command>systemd-journald</command>. Their meaning is the
 479           same as
 480           <varname>_UID=</varname>,
 481           <varname>_GID=</varname>,
 482           <varname>_COMM=</varname>,
 483           <varname>_EXE=</varname>,
 484           <varname>_CMDLINE=</varname>,
 485           <varname>_AUDIT_SESSION=</varname>,
 486           <varname>_AUDIT_LOGINUID=</varname>,
 487           <varname>_SYSTEMD_CGROUP=</varname>,
 488           <varname>_SYSTEMD_SESSION=</varname>,
 489           <varname>_SYSTEMD_UNIT=</varname>,
 490           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 491           <varname>_SYSTEMD_OWNER_UID=</varname>
 492           as described above, except that the process identified by
 493           <replaceable>PID</replaceable> is described, instead of the
 494           process which logged the message.</para>
 495         </listitem>
 496       </varlistentry>
 497     </variablelist>
 498
 499   </refsect1>
 500
 501   <refsect1>
 502     <title>Address Fields</title>
 503
 504     <para>During serialization into external formats, such as the
 505     <ulink
 506     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 507     Export Format</ulink> or the <ulink
 508     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 509     JSON Format</ulink>, the addresses of journal entries are
 510     serialized into fields prefixed with double underscores. Note that
 511     these are not proper fields when stored in the journal but for
 512     addressing metadata of entries. They cannot be written as part of
 513     structured log entries via calls such as
 514     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 515     They may also not be used as matches for
 516     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
 517
 518     <variablelist class='journal-directives'>
 519       <varlistentry>
 520         <term><varname>__CURSOR=</varname></term>
 521         <listitem>
 522           <para>The cursor for the entry. A cursor is an opaque text
 523           string that uniquely describes the position of an entry in
 524           the journal and is portable across machines, platforms and
 525           journal files.
 526           </para>
 527         </listitem>
 528       </varlistentry>
 529
 530       <varlistentry>
 531         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 532         <listitem>
 533           <para>The wallclock time
 534           (<constant>CLOCK_REALTIME</constant>) at the point in time
 535           the entry was received by the journal, in microseconds since
 536           the epoch UTC, formatted as a decimal string. This has
 537           different properties from
 538           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 539           usually a bit later but more likely to be monotonic.
 540           </para>
 541         </listitem>
 542       </varlistentry>
 543
 544       <varlistentry>
 545         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 546         <listitem>
 547           <para>The monotonic time
 548           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 549           the entry was received by the journal in microseconds,
 550           formatted as a decimal string. To be useful as an address
 551           for the entry, this should be combined with the boot ID in
 552           <literal>_BOOT_ID=</literal>.
 553           </para>
 554         </listitem>
 555       </varlistentry>
 556     </variablelist>
 557   </refsect1>
 558
 559   <refsect1>
 560       <title>See Also</title>
 561       <para>
 562         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 563         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
 564         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 565         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 566         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 567         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 568         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 569       </para>
 570   </refsect1>
 571
 572 </refentry>