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