man/systemd.journal-fields.xml

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  23
  24 <refentry id="systemd.journal-fields">
  25
  26   <refentryinfo>
  27     <title>systemd.journal-fields</title>
  28     <productname>systemd</productname>
  29
  30     <authorgroup>
  31       <author>
  32         <contrib>Developer</contrib>
  33         <firstname>Lennart</firstname>
  34         <surname>Poettering</surname>
  35         <email>lennart@poettering.net</email>
  36       </author>
  37     </authorgroup>
  38   </refentryinfo>
  39
  40   <refmeta>
  41     <refentrytitle>systemd.journal-fields</refentrytitle>
  42     <manvolnum>7</manvolnum>
  43   </refmeta>
  44
  45   <refnamediv>
  46     <refname>systemd.journal-fields</refname>
  47     <refpurpose>Special journal fields</refpurpose>
  48   </refnamediv>
  49
  50   <refsect1>
  51     <title>Description</title>
  52
  53     <para>Entries in the journal resemble an environment block in
  54     their syntax but with fields that can include binary data.
  55     Primarily, fields are formatted UTF-8 text strings, and binary
  56     formatting is used only where formatting as UTF-8 text strings
  57     makes little sense. New fields may freely be defined by
  58     applications, but a few fields have special meaning. All fields
  59     with special meanings are optional. In some cases, fields may
  60     appear more than once per entry.</para>
  61   </refsect1>
  62
  63   <refsect1>
  64     <title>User Journal Fields</title>
  65
  66     <para>User fields are fields that are directly passed from clients
  67     and stored in the journal.</para>
  68
  69     <variablelist class='journal-directives'>
  70       <varlistentry>
  71         <term><varname>MESSAGE=</varname></term>
  72         <listitem>
  73           <para>The human-readable message string for this entry. This
  74           is supposed to be the primary text shown to the user. It is
  75           usually not translated (but might be in some cases), and is
  76           not supposed to be parsed for metadata.</para>
  77         </listitem>
  78       </varlistentry>
  79
  80       <varlistentry>
  81         <term><varname>MESSAGE_ID=</varname></term>
  82         <listitem>
  83           <para>A 128-bit message identifier ID for recognizing
  84           certain message types, if this is desirable. This should
  85           contain a 128-bit ID formatted as a lower-case hexadecimal
  86           string, without any separating dashes or suchlike. This is
  87           recommended to be a UUID-compatible ID, but this is not
  88           enforced, and formatted differently. Developers can generate
  89           a new ID for this purpose with <command>journalctl
  90           <option>--new-id128</option></command>.
  91           </para>
  92         </listitem>
  93       </varlistentry>
  94
  95       <varlistentry>
  96         <term><varname>PRIORITY=</varname></term>
  97         <listitem>
  98           <para>A priority value between 0 (<literal>emerg</literal>)
  99           and 7 (<literal>debug</literal>) formatted as a decimal
 100           string. This field is compatible with syslog's priority
 101           concept.</para>
 102         </listitem>
 103       </varlistentry>
 104
 105       <varlistentry>
 106         <term><varname>CODE_FILE=</varname></term>
 107         <term><varname>CODE_LINE=</varname></term>
 108         <term><varname>CODE_FUNC=</varname></term>
 109         <listitem>
 110           <para>The code location generating this message, if known.
 111           Contains the source filename, the line number and the
 112           function name.</para>
 113         </listitem>
 114       </varlistentry>
 115
 116       <varlistentry>
 117         <term><varname>ERRNO=</varname></term>
 118         <listitem>
 119           <para>The low-level Unix error number causing this entry, if
 120           any. Contains the numeric value of
 121           <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 122           formatted as a decimal string.</para>
 123         </listitem>
 124       </varlistentry>
 125
 126       <varlistentry>
 127         <term><varname>SYSLOG_FACILITY=</varname></term>
 128         <term><varname>SYSLOG_IDENTIFIER=</varname></term>
 129         <term><varname>SYSLOG_PID=</varname></term>
 130         <listitem>
 131           <para>Syslog compatibility fields containing the facility
 132           (formatted as decimal string), the identifier string (i.e.
 133           "tag"), and the client PID. (Note that the tag is usually
 134           derived from glibc's
 135           <varname>program_invocation_short_name</varname> variable,
 136           see
 137           <citerefentry project='die-net'><refentrytitle>program_invocation_short_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>.)</para>
 138         </listitem>
 139
 140       </varlistentry>
 141     </variablelist>
 142   </refsect1>
 143
 144   <refsect1>
 145     <title>Trusted Journal Fields</title>
 146
 147     <para>Fields prefixed with an underscore are trusted fields, i.e.
 148     fields that are implicitly added by the journal and cannot be
 149     altered by client code.</para>
 150
 151     <variablelist class='journal-directives'>
 152       <varlistentry>
 153         <term><varname>_PID=</varname></term>
 154         <term><varname>_UID=</varname></term>
 155         <term><varname>_GID=</varname></term>
 156         <listitem>
 157           <para>The process, user, and group ID of the process the
 158           journal entry originates from formatted as a decimal
 159           string. Note that entries obtained via <literal>stdout</literal> or
 160           <literal>stderr</literal> of forked processes will contain credentials valid for a parent
 161           process (that initiated the connection to <command>systemd-journald</command>).</para>
 162         </listitem>
 163       </varlistentry>
 164
 165       <varlistentry>
 166         <term><varname>_COMM=</varname></term>
 167         <term><varname>_EXE=</varname></term>
 168         <term><varname>_CMDLINE=</varname></term>
 169         <listitem>
 170           <para>The name, the executable path, and the command line of
 171           the process the journal entry originates from.</para>
 172         </listitem>
 173       </varlistentry>
 174
 175       <varlistentry>
 176         <term><varname>_CAP_EFFECTIVE=</varname></term>
 177         <listitem>
 178           <para>The effective
 179           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 180           of the process the journal entry originates from.</para>
 181         </listitem>
 182       </varlistentry>
 183
 184       <varlistentry>
 185         <term><varname>_AUDIT_SESSION=</varname></term>
 186         <term><varname>_AUDIT_LOGINUID=</varname></term>
 187         <listitem>
 188           <para>The session and login UID of the process the journal
 189           entry originates from, as maintained by the kernel audit
 190           subsystem.</para>
 191         </listitem>
 192       </varlistentry>
 193
 194       <varlistentry>
 195         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 196         <term><varname>_SYSTEMD_SESSION=</varname></term>
 197         <term><varname>_SYSTEMD_UNIT=</varname></term>
 198         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 199         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 200         <term><varname>_SYSTEMD_SLICE=</varname></term>
 201
 202         <listitem>
 203           <para>The control group path in the systemd hierarchy, the
 204           systemd session ID (if any), the systemd unit name (if any),
 205           the systemd user session unit name (if any), the owner UID
 206           of the systemd session (if any) and the systemd slice unit
 207           of the process the journal entry originates from.</para>
 208         </listitem>
 209       </varlistentry>
 210
 211       <varlistentry>
 212         <term><varname>_SELINUX_CONTEXT=</varname></term>
 213         <listitem>
 214           <para>The SELinux security context (label) of the process
 215           the journal entry originates from.</para>
 216         </listitem>
 217       </varlistentry>
 218
 219       <varlistentry>
 220         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 221         <listitem>
 222           <para>The earliest trusted timestamp of the message, if any
 223           is known that is different from the reception time of the
 224           journal. This is the time in microseconds since the epoch
 225           UTC, formatted as a decimal string.</para>
 226         </listitem>
 227       </varlistentry>
 228
 229       <varlistentry>
 230         <term><varname>_BOOT_ID=</varname></term>
 231         <listitem>
 232           <para>The kernel boot ID for the boot the message was
 233           generated in, formatted as a 128-bit hexadecimal
 234           string.</para>
 235         </listitem>
 236       </varlistentry>
 237
 238       <varlistentry>
 239         <term><varname>_MACHINE_ID=</varname></term>
 240         <listitem>
 241           <para>The machine ID of the originating host, as available
 242           in
 243           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 244         </listitem>
 245       </varlistentry>
 246
 247       <varlistentry>
 248         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 249         <listitem>
 250           <para>The invocation ID for the runtime cycle of the unit
 251           the message was generated in, as available to processes
 252           of the unit in <varname>$INVOCATION_ID</varname> (see
 253           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 254         </listitem>
 255       </varlistentry>
 256
 257       <varlistentry>
 258         <term><varname>_HOSTNAME=</varname></term>
 259         <listitem>
 260           <para>The name of the originating host.</para>
 261         </listitem>
 262       </varlistentry>
 263
 264       <varlistentry>
 265         <term><varname>_TRANSPORT=</varname></term>
 266         <listitem>
 267           <para>How the entry was received by the journal service.
 268           Valid transports are:
 269           </para>
 270           <variablelist>
 271             <varlistentry>
 272               <term>
 273                 <option>audit</option>
 274               </term>
 275               <listitem>
 276                 <para>for those read from the kernel audit subsystem
 277                 </para>
 278               </listitem>
 279             </varlistentry>
 280
 281             <varlistentry>
 282               <term>
 283                 <option>driver</option>
 284               </term>
 285               <listitem>
 286                 <para>for internally generated messages
 287                 </para>
 288               </listitem>
 289             </varlistentry>
 290
 291             <varlistentry>
 292               <term>
 293                 <option>syslog</option>
 294               </term>
 295               <listitem>
 296                 <para>for those received via the local syslog socket
 297                 with the syslog protocol
 298                 </para>
 299               </listitem>
 300             </varlistentry>
 301
 302             <varlistentry>
 303               <term>
 304                 <option>journal</option>
 305               </term>
 306               <listitem>
 307                 <para>for those received via the native journal
 308                 protocol
 309                 </para>
 310               </listitem>
 311             </varlistentry>
 312
 313             <varlistentry>
 314               <term>
 315                 <option>stdout</option>
 316               </term>
 317               <listitem>
 318                 <para>for those read from a service's standard output
 319                 or error output
 320                 </para>
 321               </listitem>
 322             </varlistentry>
 323
 324             <varlistentry>
 325               <term>
 326                 <option>kernel</option>
 327               </term>
 328               <listitem>
 329                 <para>for those read from the kernel
 330                 </para>
 331               </listitem>
 332             </varlistentry>
 333           </variablelist>
 334         </listitem>
 335       </varlistentry>
 336       <varlistentry>
 337         <term><varname>_STREAM_ID=</varname></term>
 338         <listitem>
 339           <para>Only applies to <literal>_TRANSPORT=stream</literal> records: specifies a randomized 128bit ID assigned
 340           to the stream connection when it was first created. This ID is useful to reconstruct individual log streams
 341           from the log records: all log records carrying the same stream ID originate from the same stream.</para>
 342         </listitem>
 343       </varlistentry>
 344       <varlistentry>
 345         <term><varname>_LINE_BREAK=</varname></term>
 346         <listitem>
 347           <para>Only applies to <literal>_TRANSPORT=stream</literal> records: indicates that the log message in the
 348           standard output/error stream was not terminated with a normal newline character (<literal>\n</literal>,
 349           i.e. ASCII 10). Specifically, when set this field is one of <option>nul</option> (in case the line was
 350           terminated by a NUL byte), <option>line-max</option> (in case the maximum log line length was reached, as
 351           configured with <varname>LineMax=</varname> in
 352           <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>) or
 353           <option>eof</option> (if this was the last log record of a stream and the stream ended without a final
 354           newline character). Note that this record is not generated when a normal newline character was used for
 355           marking the log line end.</para>
 356         </listitem>
 357       </varlistentry>
 358     </variablelist>
 359   </refsect1>
 360
 361   <refsect1>
 362     <title>Kernel Journal Fields</title>
 363
 364     <para>Kernel fields are fields that are used by messages
 365     originating in the kernel and stored in the journal.</para>
 366
 367     <variablelist class='journal-directives'>
 368       <varlistentry>
 369         <term><varname>_KERNEL_DEVICE=</varname></term>
 370         <listitem>
 371           <para>The kernel device name. If the entry is associated to
 372           a block device, the major and minor of the device node,
 373           separated by <literal>:</literal> and prefixed by
 374           <literal>b</literal>. Similar for character devices but
 375           prefixed by <literal>c</literal>. For network devices, this
 376           is the interface index prefixed by <literal>n</literal>. For
 377           all other devices, this is the subsystem name prefixed by
 378           <literal>+</literal>, followed by <literal>:</literal>,
 379           followed by the kernel device name.</para>
 380         </listitem>
 381       </varlistentry>
 382       <varlistentry>
 383         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 384         <listitem>
 385           <para>The kernel subsystem name.</para>
 386         </listitem>
 387       </varlistentry>
 388       <varlistentry>
 389         <term><varname>_UDEV_SYSNAME=</varname></term>
 390         <listitem>
 391           <para>The kernel device name as it shows up in the device
 392           tree below <filename>/sys</filename>.</para>
 393         </listitem>
 394       </varlistentry>
 395       <varlistentry>
 396         <term><varname>_UDEV_DEVNODE=</varname></term>
 397         <listitem>
 398           <para>The device node path of this device in
 399           <filename>/dev</filename>.</para>
 400         </listitem>
 401       </varlistentry>
 402       <varlistentry>
 403         <term><varname>_UDEV_DEVLINK=</varname></term>
 404         <listitem>
 405           <para>Additional symlink names pointing to the device node
 406           in <filename>/dev</filename>. This field is frequently set
 407           more than once per entry.</para>
 408         </listitem>
 409       </varlistentry>
 410     </variablelist>
 411   </refsect1>
 412
 413   <refsect1>
 414     <title>Fields to log on behalf of a different program</title>
 415
 416     <para>Fields in this section are used by programs to specify that
 417     they are logging on behalf of another program or unit.
 418     </para>
 419
 420     <para>Fields used by the <command>systemd-coredump</command>
 421     coredump kernel helper:
 422     </para>
 423
 424     <variablelist class='journal-directives'>
 425       <varlistentry>
 426         <term><varname>COREDUMP_UNIT=</varname></term>
 427         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 428         <listitem>
 429           <para>Used to annotate messages containing coredumps from
 430           system and session units. See
 431           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 432           </para>
 433         </listitem>
 434       </varlistentry>
 435     </variablelist>
 436
 437     <para>Privileged programs (currently UID 0) may attach
 438     <varname>OBJECT_PID=</varname> to a message. This will instruct
 439     <command>systemd-journald</command> to attach additional fields on
 440     behalf of the caller:</para>
 441
 442     <variablelist class='journal-directives'>
 443       <varlistentry>
 444         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 445         <listitem>
 446           <para>PID of the program that this message pertains to.
 447           </para>
 448         </listitem>
 449       </varlistentry>
 450
 451       <varlistentry>
 452         <term><varname>OBJECT_UID=</varname></term>
 453         <term><varname>OBJECT_GID=</varname></term>
 454         <term><varname>OBJECT_COMM=</varname></term>
 455         <term><varname>OBJECT_EXE=</varname></term>
 456         <term><varname>OBJECT_CMDLINE=</varname></term>
 457         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 458         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 459         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 460         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 461         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 462         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 463         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 464         <listitem>
 465           <para>These are additional fields added automatically by
 466           <command>systemd-journald</command>. Their meaning is the
 467           same as
 468           <varname>_UID=</varname>,
 469           <varname>_GID=</varname>,
 470           <varname>_COMM=</varname>,
 471           <varname>_EXE=</varname>,
 472           <varname>_CMDLINE=</varname>,
 473           <varname>_AUDIT_SESSION=</varname>,
 474           <varname>_AUDIT_LOGINUID=</varname>,
 475           <varname>_SYSTEMD_CGROUP=</varname>,
 476           <varname>_SYSTEMD_SESSION=</varname>,
 477           <varname>_SYSTEMD_UNIT=</varname>,
 478           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 479           <varname>_SYSTEMD_OWNER_UID=</varname>
 480           as described above, except that the process identified by
 481           <replaceable>PID</replaceable> is described, instead of the
 482           process which logged the message.</para>
 483         </listitem>
 484       </varlistentry>
 485     </variablelist>
 486
 487   </refsect1>
 488
 489   <refsect1>
 490     <title>Address Fields</title>
 491
 492     <para>During serialization into external formats, such as the
 493     <ulink
 494     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 495     Export Format</ulink> or the <ulink
 496     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 497     JSON Format</ulink>, the addresses of journal entries are
 498     serialized into fields prefixed with double underscores. Note that
 499     these are not proper fields when stored in the journal but for
 500     addressing metadata of entries. They cannot be written as part of
 501     structured log entries via calls such as
 502     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 503     They may also not be used as matches for
 504     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
 505
 506     <variablelist class='journal-directives'>
 507       <varlistentry>
 508         <term><varname>__CURSOR=</varname></term>
 509         <listitem>
 510           <para>The cursor for the entry. A cursor is an opaque text
 511           string that uniquely describes the position of an entry in
 512           the journal and is portable across machines, platforms and
 513           journal files.
 514           </para>
 515         </listitem>
 516       </varlistentry>
 517
 518       <varlistentry>
 519         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 520         <listitem>
 521           <para>The wallclock time
 522           (<constant>CLOCK_REALTIME</constant>) at the point in time
 523           the entry was received by the journal, in microseconds since
 524           the epoch UTC, formatted as a decimal string. This has
 525           different properties from
 526           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 527           usually a bit later but more likely to be monotonic.
 528           </para>
 529         </listitem>
 530       </varlistentry>
 531
 532       <varlistentry>
 533         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 534         <listitem>
 535           <para>The monotonic time
 536           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 537           the entry was received by the journal in microseconds,
 538           formatted as a decimal string. To be useful as an address
 539           for the entry, this should be combined with the boot ID in
 540           <literal>_BOOT_ID=</literal>.
 541           </para>
 542         </listitem>
 543       </varlistentry>
 544     </variablelist>
 545   </refsect1>
 546
 547   <refsect1>
 548       <title>See Also</title>
 549       <para>
 550         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 551         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 552         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 553         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 554         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 555         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 556       </para>
 557   </refsect1>
 558
 559 </refentry>