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.</para>
 160         </listitem>
 161       </varlistentry>
 162
 163       <varlistentry>
 164         <term><varname>_COMM=</varname></term>
 165         <term><varname>_EXE=</varname></term>
 166         <term><varname>_CMDLINE=</varname></term>
 167         <listitem>
 168           <para>The name, the executable path, and the command line of
 169           the process the journal entry originates from.</para>
 170         </listitem>
 171       </varlistentry>
 172
 173       <varlistentry>
 174         <term><varname>_CAP_EFFECTIVE=</varname></term>
 175         <listitem>
 176           <para>The effective
 177           <citerefentry project='man-pages'><refentrytitle>capabilities</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 178           of the process the journal entry originates from.</para>
 179         </listitem>
 180       </varlistentry>
 181
 182       <varlistentry>
 183         <term><varname>_AUDIT_SESSION=</varname></term>
 184         <term><varname>_AUDIT_LOGINUID=</varname></term>
 185         <listitem>
 186           <para>The session and login UID of the process the journal
 187           entry originates from, as maintained by the kernel audit
 188           subsystem.</para>
 189         </listitem>
 190       </varlistentry>
 191
 192       <varlistentry>
 193         <term><varname>_SYSTEMD_CGROUP=</varname></term>
 194         <term><varname>_SYSTEMD_SESSION=</varname></term>
 195         <term><varname>_SYSTEMD_UNIT=</varname></term>
 196         <term><varname>_SYSTEMD_USER_UNIT=</varname></term>
 197         <term><varname>_SYSTEMD_OWNER_UID=</varname></term>
 198         <term><varname>_SYSTEMD_SLICE=</varname></term>
 199
 200         <listitem>
 201           <para>The control group path in the systemd hierarchy, the
 202           systemd session ID (if any), the systemd unit name (if any),
 203           the systemd user session unit name (if any), the owner UID
 204           of the systemd session (if any) and the systemd slice unit
 205           of the process the journal entry originates from.</para>
 206         </listitem>
 207       </varlistentry>
 208
 209       <varlistentry>
 210         <term><varname>_SELINUX_CONTEXT=</varname></term>
 211         <listitem>
 212           <para>The SELinux security context (label) of the process
 213           the journal entry originates from.</para>
 214         </listitem>
 215       </varlistentry>
 216
 217       <varlistentry>
 218         <term><varname>_SOURCE_REALTIME_TIMESTAMP=</varname></term>
 219         <listitem>
 220           <para>The earliest trusted timestamp of the message, if any
 221           is known that is different from the reception time of the
 222           journal. This is the time in microseconds since the epoch
 223           UTC, formatted as a decimal string.</para>
 224         </listitem>
 225       </varlistentry>
 226
 227       <varlistentry>
 228         <term><varname>_BOOT_ID=</varname></term>
 229         <listitem>
 230           <para>The kernel boot ID for the boot the message was
 231           generated in, formatted as a 128-bit hexadecimal
 232           string.</para>
 233         </listitem>
 234       </varlistentry>
 235
 236       <varlistentry>
 237         <term><varname>_MACHINE_ID=</varname></term>
 238         <listitem>
 239           <para>The machine ID of the originating host, as available
 240           in
 241           <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 242         </listitem>
 243       </varlistentry>
 244
 245       <varlistentry>
 246         <term><varname>_SYSTEMD_INVOCATION_ID=</varname></term>
 247         <listitem>
 248           <para>The invocation ID for the runtime cycle of the unit
 249           the message was generated in, as available to processes
 250           of the unit in <varname>$INVOCATION_ID</varname> (see
 251           <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>).</para>
 252         </listitem>
 253       </varlistentry>
 254
 255       <varlistentry>
 256         <term><varname>_HOSTNAME=</varname></term>
 257         <listitem>
 258           <para>The name of the originating host.</para>
 259         </listitem>
 260       </varlistentry>
 261
 262       <varlistentry>
 263         <term><varname>_TRANSPORT=</varname></term>
 264         <listitem>
 265           <para>How the entry was received by the journal service.
 266           Valid transports are:
 267           </para>
 268           <variablelist>
 269             <varlistentry>
 270               <term>
 271                 <option>audit</option>
 272               </term>
 273               <listitem>
 274                 <para>for those read from the kernel audit subsystem
 275                 </para>
 276               </listitem>
 277             </varlistentry>
 278
 279             <varlistentry>
 280               <term>
 281                 <option>driver</option>
 282               </term>
 283               <listitem>
 284                 <para>for internally generated messages
 285                 </para>
 286               </listitem>
 287             </varlistentry>
 288
 289             <varlistentry>
 290               <term>
 291                 <option>syslog</option>
 292               </term>
 293               <listitem>
 294                 <para>for those received via the local syslog socket
 295                 with the syslog protocol
 296                 </para>
 297               </listitem>
 298             </varlistentry>
 299
 300             <varlistentry>
 301               <term>
 302                 <option>journal</option>
 303               </term>
 304               <listitem>
 305                 <para>for those received via the native journal
 306                 protocol
 307                 </para>
 308               </listitem>
 309             </varlistentry>
 310
 311             <varlistentry>
 312               <term>
 313                 <option>stdout</option>
 314               </term>
 315               <listitem>
 316                 <para>for those read from a service's standard output
 317                 or error output
 318                 </para>
 319               </listitem>
 320             </varlistentry>
 321
 322             <varlistentry>
 323               <term>
 324                 <option>kernel</option>
 325               </term>
 326               <listitem>
 327                 <para>for those read from the kernel
 328                 </para>
 329               </listitem>
 330             </varlistentry>
 331           </variablelist>
 332         </listitem>
 333       </varlistentry>
 334     </variablelist>
 335   </refsect1>
 336
 337   <refsect1>
 338     <title>Kernel Journal Fields</title>
 339
 340     <para>Kernel fields are fields that are used by messages
 341     originating in the kernel and stored in the journal.</para>
 342
 343     <variablelist class='journal-directives'>
 344       <varlistentry>
 345         <term><varname>_KERNEL_DEVICE=</varname></term>
 346         <listitem>
 347           <para>The kernel device name. If the entry is associated to
 348           a block device, the major and minor of the device node,
 349           separated by <literal>:</literal> and prefixed by
 350           <literal>b</literal>. Similar for character devices but
 351           prefixed by <literal>c</literal>. For network devices, this
 352           is the interface index prefixed by <literal>n</literal>. For
 353           all other devices, this is the subsystem name prefixed by
 354           <literal>+</literal>, followed by <literal>:</literal>,
 355           followed by the kernel device name.</para>
 356         </listitem>
 357       </varlistentry>
 358       <varlistentry>
 359         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 360         <listitem>
 361           <para>The kernel subsystem name.</para>
 362         </listitem>
 363       </varlistentry>
 364       <varlistentry>
 365         <term><varname>_UDEV_SYSNAME=</varname></term>
 366         <listitem>
 367           <para>The kernel device name as it shows up in the device
 368           tree below <filename>/sys</filename>.</para>
 369         </listitem>
 370       </varlistentry>
 371       <varlistentry>
 372         <term><varname>_UDEV_DEVNODE=</varname></term>
 373         <listitem>
 374           <para>The device node path of this device in
 375           <filename>/dev</filename>.</para>
 376         </listitem>
 377       </varlistentry>
 378       <varlistentry>
 379         <term><varname>_UDEV_DEVLINK=</varname></term>
 380         <listitem>
 381           <para>Additional symlink names pointing to the device node
 382           in <filename>/dev</filename>. This field is frequently set
 383           more than once per entry.</para>
 384         </listitem>
 385       </varlistentry>
 386     </variablelist>
 387   </refsect1>
 388
 389   <refsect1>
 390     <title>Fields to log on behalf of a different program</title>
 391
 392     <para>Fields in this section are used by programs to specify that
 393     they are logging on behalf of another program or unit.
 394     </para>
 395
 396     <para>Fields used by the <command>systemd-coredump</command>
 397     coredump kernel helper:
 398     </para>
 399
 400     <variablelist class='journal-directives'>
 401       <varlistentry>
 402         <term><varname>COREDUMP_UNIT=</varname></term>
 403         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 404         <listitem>
 405           <para>Used to annotate messages containing coredumps from
 406           system and session units. See
 407           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 408           </para>
 409         </listitem>
 410       </varlistentry>
 411     </variablelist>
 412
 413     <para>Privileged programs (currently UID 0) may attach
 414     <varname>OBJECT_PID=</varname> to a message. This will instruct
 415     <command>systemd-journald</command> to attach additional fields on
 416     behalf of the caller:</para>
 417
 418     <variablelist class='journal-directives'>
 419       <varlistentry>
 420         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 421         <listitem>
 422           <para>PID of the program that this message pertains to.
 423           </para>
 424         </listitem>
 425       </varlistentry>
 426
 427       <varlistentry>
 428         <term><varname>OBJECT_UID=</varname></term>
 429         <term><varname>OBJECT_GID=</varname></term>
 430         <term><varname>OBJECT_COMM=</varname></term>
 431         <term><varname>OBJECT_EXE=</varname></term>
 432         <term><varname>OBJECT_CMDLINE=</varname></term>
 433         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 434         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 435         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 436         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 437         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 438         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 439         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 440         <listitem>
 441           <para>These are additional fields added automatically by
 442           <command>systemd-journald</command>. Their meaning is the
 443           same as
 444           <varname>_UID=</varname>,
 445           <varname>_GID=</varname>,
 446           <varname>_COMM=</varname>,
 447           <varname>_EXE=</varname>,
 448           <varname>_CMDLINE=</varname>,
 449           <varname>_AUDIT_SESSION=</varname>,
 450           <varname>_AUDIT_LOGINUID=</varname>,
 451           <varname>_SYSTEMD_CGROUP=</varname>,
 452           <varname>_SYSTEMD_SESSION=</varname>,
 453           <varname>_SYSTEMD_UNIT=</varname>,
 454           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 455           <varname>_SYSTEMD_OWNER_UID=</varname>
 456           as described above, except that the process identified by
 457           <replaceable>PID</replaceable> is described, instead of the
 458           process which logged the message.</para>
 459         </listitem>
 460       </varlistentry>
 461     </variablelist>
 462
 463   </refsect1>
 464
 465   <refsect1>
 466     <title>Address Fields</title>
 467
 468     <para>During serialization into external formats, such as the
 469     <ulink
 470     url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal
 471     Export Format</ulink> or the <ulink
 472     url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal
 473     JSON Format</ulink>, the addresses of journal entries are
 474     serialized into fields prefixed with double underscores. Note that
 475     these are not proper fields when stored in the journal but for
 476     addressing metadata of entries. They cannot be written as part of
 477     structured log entries via calls such as
 478     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 479     They may also not be used as matches for
 480     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
 481
 482     <variablelist class='journal-directives'>
 483       <varlistentry>
 484         <term><varname>__CURSOR=</varname></term>
 485         <listitem>
 486           <para>The cursor for the entry. A cursor is an opaque text
 487           string that uniquely describes the position of an entry in
 488           the journal and is portable across machines, platforms and
 489           journal files.
 490           </para>
 491         </listitem>
 492       </varlistentry>
 493
 494       <varlistentry>
 495         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 496         <listitem>
 497           <para>The wallclock time
 498           (<constant>CLOCK_REALTIME</constant>) at the point in time
 499           the entry was received by the journal, in microseconds since
 500           the epoch UTC, formatted as a decimal string. This has
 501           different properties from
 502           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 503           usually a bit later but more likely to be monotonic.
 504           </para>
 505         </listitem>
 506       </varlistentry>
 507
 508       <varlistentry>
 509         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 510         <listitem>
 511           <para>The monotonic time
 512           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 513           the entry was received by the journal in microseconds,
 514           formatted as a decimal string. To be useful as an address
 515           for the entry, this should be combined with the boot ID in
 516           <literal>_BOOT_ID=</literal>.
 517           </para>
 518         </listitem>
 519       </varlistentry>
 520     </variablelist>
 521   </refsect1>
 522
 523   <refsect1>
 524       <title>See Also</title>
 525       <para>
 526         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 527         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 528         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 529         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 530         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 531         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 532       </para>
 533   </refsect1>
 534
 535 </refentry>