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 meta data.</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-id</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>_HOSTNAME=</varname></term>
 247         <listitem>
 248           <para>The name of the originating host.</para>
 249         </listitem>
 250       </varlistentry>
 251
 252       <varlistentry>
 253         <term><varname>_TRANSPORT=</varname></term>
 254         <listitem>
 255           <para>How the entry was received by the journal service.
 256           Valid transports are:
 257           </para>
 258           <variablelist>
 259             <varlistentry>
 260               <term>
 261                 <option>driver</option>
 262               </term>
 263               <listitem>
 264                 <para>for internally generated messages
 265                 </para>
 266               </listitem>
 267             </varlistentry>
 268
 269             <varlistentry>
 270               <term>
 271                 <option>syslog</option>
 272               </term>
 273               <listitem>
 274                 <para>for those received via the local syslog socket
 275                 with the syslog protocol
 276                 </para>
 277               </listitem>
 278             </varlistentry>
 279
 280             <varlistentry>
 281               <term>
 282                 <option>journal</option>
 283               </term>
 284               <listitem>
 285                 <para>for those received via the native journal
 286                 protocol
 287                 </para>
 288               </listitem>
 289             </varlistentry>
 290
 291             <varlistentry>
 292               <term>
 293                 <option>stdout</option>
 294               </term>
 295               <listitem>
 296                 <para>for those read from a service's standard output
 297                 or error output
 298                 </para>
 299               </listitem>
 300             </varlistentry>
 301
 302             <varlistentry>
 303               <term>
 304                 <option>kernel</option>
 305               </term>
 306               <listitem>
 307                 <para>for those read from the kernel
 308                 </para>
 309               </listitem>
 310             </varlistentry>
 311           </variablelist>
 312         </listitem>
 313       </varlistentry>
 314     </variablelist>
 315   </refsect1>
 316
 317   <refsect1>
 318     <title>Kernel Journal Fields</title>
 319
 320     <para>Kernel fields are fields that are used by messages
 321     originating in the kernel and stored in the journal.</para>
 322
 323     <variablelist class='journal-directives'>
 324       <varlistentry>
 325         <term><varname>_KERNEL_DEVICE=</varname></term>
 326         <listitem>
 327           <para>The kernel device name. If the entry is associated to
 328           a block device, the major and minor of the device node,
 329           separated by <literal>:</literal> and prefixed by
 330           <literal>b</literal>. Similar for character devices but
 331           prefixed by <literal>c</literal>. For network devices, this
 332           is the interface index prefixed by <literal>n</literal>. For
 333           all other devices, this is the subsystem name prefixed by
 334           <literal>+</literal>, followed by <literal>:</literal>,
 335           followed by the kernel device name.</para>
 336         </listitem>
 337       </varlistentry>
 338       <varlistentry>
 339         <term><varname>_KERNEL_SUBSYSTEM=</varname></term>
 340         <listitem>
 341           <para>The kernel subsystem name.</para>
 342         </listitem>
 343       </varlistentry>
 344       <varlistentry>
 345         <term><varname>_UDEV_SYSNAME=</varname></term>
 346         <listitem>
 347           <para>The kernel device name as it shows up in the device
 348           tree below <filename>/sys</filename>.</para>
 349         </listitem>
 350       </varlistentry>
 351       <varlistentry>
 352         <term><varname>_UDEV_DEVNODE=</varname></term>
 353         <listitem>
 354           <para>The device node path of this device in
 355           <filename>/dev</filename>.</para>
 356         </listitem>
 357       </varlistentry>
 358       <varlistentry>
 359         <term><varname>_UDEV_DEVLINK=</varname></term>
 360         <listitem>
 361           <para>Additional symlink names pointing to the device node
 362           in <filename>/dev</filename>. This field is frequently set
 363           more than once per entry.</para>
 364         </listitem>
 365       </varlistentry>
 366     </variablelist>
 367   </refsect1>
 368
 369   <refsect1>
 370     <title>Fields to log on behalf of a different program</title>
 371
 372     <para>Fields in this section are used by programs to specify that
 373     they are logging on behalf of another program or unit.
 374     </para>
 375
 376     <para>Fields used by the <command>systemd-coredump</command>
 377     coredump kernel helper:
 378     </para>
 379
 380     <variablelist class='journal-directives'>
 381       <varlistentry>
 382         <term><varname>COREDUMP_UNIT=</varname></term>
 383         <term><varname>COREDUMP_USER_UNIT=</varname></term>
 384         <listitem>
 385           <para>Used to annotate messages containing coredumps from
 386           system and session units. See
 387           <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>.
 388           </para>
 389         </listitem>
 390       </varlistentry>
 391     </variablelist>
 392
 393     <para>Privileged programs (currently UID 0) may attach
 394     <varname>OBJECT_PID=</varname> to a message. This will instruct
 395     <command>systemd-journald</command> to attach additional fields on
 396     behalf of the caller:</para>
 397
 398     <variablelist class='journal-directives'>
 399       <varlistentry>
 400         <term><varname>OBJECT_PID=<replaceable>PID</replaceable></varname></term>
 401         <listitem>
 402           <para>PID of the program that this message pertains to.
 403           </para>
 404         </listitem>
 405       </varlistentry>
 406
 407       <varlistentry>
 408         <term><varname>OBJECT_UID=</varname></term>
 409         <term><varname>OBJECT_GID=</varname></term>
 410         <term><varname>OBJECT_COMM=</varname></term>
 411         <term><varname>OBJECT_EXE=</varname></term>
 412         <term><varname>OBJECT_CMDLINE=</varname></term>
 413         <term><varname>OBJECT_AUDIT_SESSION=</varname></term>
 414         <term><varname>OBJECT_AUDIT_LOGINUID=</varname></term>
 415         <term><varname>OBJECT_SYSTEMD_CGROUP=</varname></term>
 416         <term><varname>OBJECT_SYSTEMD_SESSION=</varname></term>
 417         <term><varname>OBJECT_SYSTEMD_OWNER_UID=</varname></term>
 418         <term><varname>OBJECT_SYSTEMD_UNIT=</varname></term>
 419         <term><varname>OBJECT_SYSTEMD_USER_UNIT=</varname></term>
 420         <listitem>
 421           <para>These are additional fields added automatically by
 422           <command>systemd-journald</command>. Their meaning is the
 423           same as
 424           <varname>_UID=</varname>,
 425           <varname>_GID=</varname>,
 426           <varname>_COMM=</varname>,
 427           <varname>_EXE=</varname>,
 428           <varname>_CMDLINE=</varname>,
 429           <varname>_AUDIT_SESSION=</varname>,
 430           <varname>_AUDIT_LOGINUID=</varname>,
 431           <varname>_SYSTEMD_CGROUP=</varname>,
 432           <varname>_SYSTEMD_SESSION=</varname>,
 433           <varname>_SYSTEMD_UNIT=</varname>,
 434           <varname>_SYSTEMD_USER_UNIT=</varname>, and
 435           <varname>_SYSTEMD_OWNER_UID=</varname>
 436           as described above, except that the process identified by
 437           <replaceable>PID</replaceable> is described, instead of the
 438           process which logged the message.</para>
 439         </listitem>
 440       </varlistentry>
 441     </variablelist>
 442
 443
 444   </refsect1>
 445
 446   <refsect1>
 447     <title>Address Fields</title>
 448
 449     <para>During serialization into external formats, such as the
 450     <ulink
 451     url="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
 452     Export Format</ulink> or the <ulink
 453     url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
 454     JSON Format</ulink>, the addresses of journal entries are
 455     serialized into fields prefixed with double underscores. Note that
 456     these are not proper fields when stored in the journal but for
 457     addressing metadata of entries. They cannot be written as part of
 458     structured log entries via calls such as
 459     <citerefentry><refentrytitle>sd_journal_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 460     They may also not be used as matches for
 461     <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry></para>
 462
 463     <variablelist class='journal-directives'>
 464       <varlistentry>
 465         <term><varname>__CURSOR=</varname></term>
 466         <listitem>
 467           <para>The cursor for the entry. A cursor is an opaque text
 468           string that uniquely describes the position of an entry in
 469           the journal and is portable across machines, platforms and
 470           journal files.
 471           </para>
 472         </listitem>
 473       </varlistentry>
 474
 475       <varlistentry>
 476         <term><varname>__REALTIME_TIMESTAMP=</varname></term>
 477         <listitem>
 478           <para>The wallclock time
 479           (<constant>CLOCK_REALTIME</constant>) at the point in time
 480           the entry was received by the journal, in microseconds since
 481           the epoch UTC, formatted as a decimal string. This has
 482           different properties from
 483           <literal>_SOURCE_REALTIME_TIMESTAMP=</literal>, as it is
 484           usually a bit later but more likely to be monotonic.
 485           </para>
 486         </listitem>
 487       </varlistentry>
 488
 489       <varlistentry>
 490         <term><varname>__MONOTONIC_TIMESTAMP=</varname></term>
 491         <listitem>
 492           <para>The monotonic time
 493           (<constant>CLOCK_MONOTONIC</constant>) at the point in time
 494           the entry was received by the journal in microseconds,
 495           formatted as a decimal string. To be useful as an address
 496           for the entry, this should be combined with the boot ID in
 497           <literal>_BOOT_ID=</literal>.
 498           </para>
 499         </listitem>
 500       </varlistentry>
 501     </variablelist>
 502   </refsect1>
 503
 504   <refsect1>
 505       <title>See Also</title>
 506       <para>
 507         <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 508         <citerefentry><refentrytitle>journalctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 509         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
 510         <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 511         <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
 512         <citerefentry><refentrytitle>systemd.directives</refentrytitle><manvolnum>7</manvolnum></citerefentry>
 513       </para>
 514   </refsect1>
 515
 516 </refentry>