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