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