man/systemd.journal-fields.xml

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