man/journalctl.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-or-later -->
   5
   6 <refentry id="journalctl"
   7           xmlns:xi="http://www.w3.org/2001/XInclude">
   8
   9   <refentryinfo>
  10     <title>journalctl</title>
  11     <productname>systemd</productname>
  12   </refentryinfo>
  13
  14   <refmeta>
  15     <refentrytitle>journalctl</refentrytitle>
  16     <manvolnum>1</manvolnum>
  17   </refmeta>
  18
  19   <refnamediv>
  20     <refname>journalctl</refname>
  21     <refpurpose>Print log entries from the systemd journal</refpurpose>
  22   </refnamediv>
  23
  24   <refsynopsisdiv>
  25     <cmdsynopsis>
  26       <command>journalctl</command>
  27       <arg choice="opt" rep="repeat">OPTIONS</arg>
  28       <arg choice="opt" rep="repeat">MATCHES</arg>
  29     </cmdsynopsis>
  30   </refsynopsisdiv>
  31
  32   <refsect1>
  33     <title>Description</title>
  34
  35     <para><command>journalctl</command> is used to print the log entries stored in the journal by
  36     <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  37     and
  38     <citerefentry><refentrytitle>systemd-journal-remote.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
  39     </para>
  40
  41     <para>If called without parameters, it will show the contents of the journal accessible to the calling
  42     user, starting with the oldest entry collected.</para>
  43
  44     <para>If one or more match arguments are passed, the output is filtered accordingly. A match is in the
  45     format <literal>FIELD=VALUE</literal>, e.g. <literal>_SYSTEMD_UNIT=httpd.service</literal>, referring to
  46     the components of a structured journal entry. See
  47     <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
  48     for a list of well-known fields. If multiple matches are specified matching different fields, the log
  49     entries are filtered by both, i.e. the resulting output will show only entries matching all the specified
  50     matches of this kind. If two matches apply to the same field, then they are automatically matched as
  51     alternatives, i.e. the resulting output will show entries matching any of the specified matches for the
  52     same field. Finally, the character <literal>+</literal> may appear as a separate word between other terms
  53     on the command line. This causes all matches before and after to be combined in a disjunction
  54     (i.e. logical OR).</para>
  55
  56     <para>It is also possible to filter the entries by specifying an absolute file path as an argument. The
  57     file path may be a file or a symbolic link and the file must exist at the time of the query. If a file
  58     path refers to an executable binary, an <literal>_EXE=</literal> match for the canonicalized binary path
  59     is added to the query. If a file path refers to an executable script, a <literal>_COMM=</literal> match
  60     for the script name is added to the query. If a file path refers to a device node,
  61     <literal>_KERNEL_DEVICE=</literal> matches for the kernel name of the device and for each of its ancestor
  62     devices is added to the query. Symbolic links are dereferenced, kernel names are synthesized, and parent
  63     devices are identified from the environment at the time of the query. In general, a device node is the
  64     best proxy for an actual device, as log entries do not usually contain fields that identify an actual
  65     device. For the resulting log entries to be correct for the actual device, the relevant parts of the
  66     environment at the time the entry was logged, in particular the actual device corresponding to the device
  67     node, must have been the same as those at the time of the query. Because device nodes generally change
  68     their corresponding devices across reboots, specifying a device node path causes the resulting entries to
  69     be restricted to those from the current boot.</para>
  70
  71     <para>Additional constraints may be added using options <option>--boot</option>,
  72     <option>--unit=</option>, etc., to further limit what entries will be shown (logical AND).</para>
  73
  74     <para>Output is interleaved from all accessible journal files, whether they are rotated or currently
  75     being written, and regardless of whether they belong to the system itself or are accessible user
  76     journals. The <option>--header</option> option can be used to identify which files
  77     <emphasis>are</emphasis> being shown.</para>
  78
  79     <para>The set of journal files which will be used can be modified using the <option>--user</option>,
  80     <option>--system</option>, <option>--directory</option>, and <option>--file</option> options, see
  81     below.</para>
  82
  83     <para>All users are granted access to their private per-user journals. However, by default, only root and
  84     users who are members of a few special groups are granted access to the system journal and the journals
  85     of other users. Members of the groups <literal>systemd-journal</literal>, <literal>adm</literal>, and
  86     <literal>wheel</literal> can read all journal files. Note that the two latter groups traditionally have
  87     additional privileges specified by the distribution. Members of the <literal>wheel</literal> group can
  88     often perform administrative tasks.</para>
  89
  90     <para>The output is paged through <command>less</command> by default, and long lines are "truncated" to
  91     screen width. The hidden part can be viewed by using the left-arrow and right-arrow keys. Paging can be
  92     disabled; see the <option>--no-pager</option> option and the "Environment" section below.</para>
  93
  94     <para>When outputting to a tty, lines are colored according to priority: lines of level ERROR and higher
  95     are colored red; lines of level WARNING are colored yellow; lines of level NOTICE are highlighted;
  96     lines of level INFO are displayed normally; lines of level DEBUG are colored grey.</para>
  97
  98     <para>To write entries <emphasis>to</emphasis> the journal, a few methods may be used. In general, output
  99     from systemd units is automatically connected to the journal, see
 100     <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
 101     In addition,
 102     <citerefentry><refentrytitle>systemd-cat</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 103     may be used to send messages to the journal directly.</para>
 104   </refsect1>
 105
 106   <refsect1>
 107     <title>Source Options</title>
 108
 109     <para>The following options control where to read journal records from:</para>
 110
 111     <variablelist>
 112       <varlistentry>
 113         <term><option>--system</option></term>
 114         <term><option>--user</option></term>
 115
 116         <listitem><para>Show messages from system services and the kernel (with
 117         <option>--system</option>). Show messages from service of current user (with
 118         <option>--user</option>).  If neither is specified, show all messages that the user can see.
 119         </para>
 120
 121         <para>The <option>--user</option> option affects how <option>--unit=</option> arguments are
 122         treated. See <option>--unit=</option>.</para>
 123
 124         <para>Note that <option>--user</option> only works if persistent logging is enabled, via the
 125         <varname>Storage=</varname> setting in
 126         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
 127
 128         <xi:include href="version-info.xml" xpointer="v205"/></listitem>
 129       </varlistentry>
 130
 131       <varlistentry>
 132         <term><option>-M</option></term>
 133         <term><option>--machine=</option></term>
 134
 135         <listitem><para>Show messages from a running, local container. Specify a container name to connect
 136         to.</para>
 137
 138         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 139       </varlistentry>
 140
 141       <varlistentry>
 142         <term><option>-m</option></term>
 143         <term><option>--merge</option></term>
 144
 145         <listitem><para>Show entries interleaved from all available journals, including remote
 146         ones.</para>
 147
 148         <xi:include href="version-info.xml" xpointer="v190"/></listitem>
 149       </varlistentry>
 150
 151       <varlistentry>
 152         <term><option>-D <replaceable>DIR</replaceable></option></term>
 153         <term><option>--directory=<replaceable>DIR</replaceable></option></term>
 154
 155         <listitem><para>Takes a directory path as argument. If specified, journalctl will operate on the
 156         specified journal directory <replaceable>DIR</replaceable> instead of the default runtime and system
 157         journal paths.</para>
 158
 159         <xi:include href="version-info.xml" xpointer="v187"/></listitem>
 160       </varlistentry>
 161
 162       <varlistentry>
 163         <term><option>--file=<replaceable>GLOB</replaceable></option></term>
 164
 165         <listitem><para>Takes a file glob as an argument. If specified, journalctl will operate on the
 166         specified journal files matching <replaceable>GLOB</replaceable> instead of the default runtime and
 167         system journal paths. May be specified multiple times, in which case files will be suitably
 168         interleaved.</para>
 169
 170         <xi:include href="version-info.xml" xpointer="v205"/></listitem>
 171       </varlistentry>
 172
 173       <varlistentry>
 174         <term><option>--root=<replaceable>ROOT</replaceable></option></term>
 175
 176         <listitem><para>Takes a directory path as an argument. If specified, <command>journalctl</command>
 177         will operate on journal directories and catalog file hierarchy underneath the specified directory
 178         instead of the root directory (e.g. <option>--update-catalog</option> will create
 179         <filename><replaceable>ROOT</replaceable>/var/lib/systemd/catalog/database</filename>, and journal
 180         files under <filename><replaceable>ROOT</replaceable>/run/journal/</filename> or
 181         <filename><replaceable>ROOT</replaceable>/var/log/journal/</filename> will be displayed).
 182         </para>
 183
 184         <xi:include href="version-info.xml" xpointer="v201"/></listitem>
 185       </varlistentry>
 186
 187       <varlistentry>
 188         <term><option>--image=<replaceable>IMAGE</replaceable></option></term>
 189
 190         <listitem><para>Takes a path to a disk image file or block device node. If specified,
 191         <command>journalctl</command> will operate on the file system in the indicated disk image. This
 192         option is similar to <option>--root=</option>, but operates on file systems stored in disk images or
 193         block devices, thus providing an easy way to extract log data from disk images. The disk image should
 194         either contain just a file system or a set of file systems within a GPT partition table, following
 195         the <ulink url="https://uapi-group.org/specifications/specs/discoverable_partitions_specification">Discoverable Partitions
 196         Specification</ulink>. For further information on supported disk images, see
 197         <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
 198         switch of the same name.</para>
 199
 200         <xi:include href="version-info.xml" xpointer="v247"/></listitem>
 201       </varlistentry>
 202
 203       <xi:include href="standard-options.xml" xpointer="image-policy-open" />
 204
 205       <varlistentry>
 206         <term><option>--namespace=<replaceable>NAMESPACE</replaceable></option></term>
 207
 208         <listitem><para>Takes a journal namespace identifier string as argument. If not specified the data
 209         collected by the default namespace is shown. If specified shows the log data of the specified
 210         namespace instead. If the namespace is specified as <literal>*</literal> data from all namespaces is
 211         shown, interleaved. If the namespace identifier is prefixed with <literal>+</literal> data from the
 212         specified namespace and the default namespace is shown, interleaved, but no other. For details about
 213         journal namespaces see
 214         <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 215
 216         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 217       </varlistentry>
 218     </variablelist>
 219   </refsect1>
 220
 221   <refsect1>
 222     <title>Filtering Options</title>
 223
 224     <para>The following options control how to filter journal records:</para>
 225
 226     <variablelist>
 227       <varlistentry>
 228         <term><option>-S</option></term>
 229         <term><option>--since=</option></term>
 230         <term><option>-U</option></term>
 231         <term><option>--until=</option></term>
 232
 233         <listitem><para>Start showing entries on or newer than the specified date, or on or older than the
 234         specified date, respectively. Date specifications should be of the format <literal>2012-10-30
 235         18:17:16</literal>.  If the time part is omitted, <literal>00:00:00</literal> is assumed.  If only
 236         the seconds component is omitted, <literal>:00</literal> is assumed. If the date component is
 237         omitted, the current day is assumed. Alternatively the strings <literal>yesterday</literal>,
 238         <literal>today</literal>, <literal>tomorrow</literal> are understood, which refer to 00:00:00 of the
 239         day before the current day, the current day, or the day after the current day,
 240         respectively. <literal>now</literal> refers to the current time. Finally, relative times may be
 241         specified, prefixed with <literal>-</literal> or <literal>+</literal>, referring to times before or
 242         after the current time, respectively. For complete time and date specification, see
 243         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Note
 244         that <option>--output=short-full</option> prints timestamps that follow precisely this format.
 245         </para>
 246
 247         <xi:include href="version-info.xml" xpointer="v195"/></listitem>
 248       </varlistentry>
 249
 250       <varlistentry>
 251         <term><option>-c</option></term>
 252         <term><option>--cursor=</option></term>
 253
 254         <listitem><para>Start showing entries from the location in the journal specified by the passed
 255         cursor.</para>
 256
 257         <xi:include href="version-info.xml" xpointer="v193"/></listitem>
 258       </varlistentry>
 259
 260       <varlistentry>
 261         <term><option>--after-cursor=</option></term>
 262
 263         <listitem><para>Start showing entries from the location in the journal <emphasis>after</emphasis>
 264         the location specified by the passed cursor.  The cursor is shown when the
 265         <option>--show-cursor</option> option is used.</para>
 266
 267         <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 268       </varlistentry>
 269
 270       <varlistentry>
 271         <term><option>--cursor-file=<replaceable>FILE</replaceable></option></term>
 272
 273         <listitem><para>If <replaceable>FILE</replaceable> exists and contains a cursor, start showing
 274         entries <emphasis>after</emphasis> this location.  Otherwise show entries according to the other
 275         given options. At the end, write the cursor of the last entry to
 276         <replaceable>FILE</replaceable>. Use this option to continually read the journal by sequentially
 277         calling <command>journalctl</command>.</para>
 278
 279         <xi:include href="version-info.xml" xpointer="v242"/></listitem>
 280       </varlistentry>
 281
 282       <varlistentry>
 283         <term><option>-b <optional><optional><replaceable>ID</replaceable></optional><optional><replaceable>±offset</replaceable></optional>|<constant>all</constant></optional></option></term>
 284         <term><option>--boot<optional>=<optional><replaceable>ID</replaceable></optional><optional><replaceable>±offset</replaceable></optional>|<constant>all</constant></optional></option></term>
 285
 286         <listitem><para>Show messages from a specific boot. This will add a match for
 287         <literal>_BOOT_ID=</literal>.</para>
 288
 289         <para>The argument may be empty, in which case logs for the current boot will be shown.</para>
 290
 291         <para>If the boot ID is omitted, a positive <replaceable>offset</replaceable> will look up the boots
 292         starting from the beginning of the journal, and an equal-or-less-than zero
 293         <replaceable>offset</replaceable> will look up boots starting from the end of the journal. Thus,
 294         <constant>1</constant> means the first boot found in the journal in chronological order,
 295         <constant>2</constant> the second and so on; while <constant>-0</constant> is the last boot,
 296         <constant>-1</constant> the boot before last, and so on. An empty <replaceable>offset</replaceable>
 297         is equivalent to specifying <constant>-0</constant>, except when the current boot is not the last
 298         boot (e.g. because <option>--directory</option> was specified to look at logs from a different
 299         machine).</para>
 300
 301         <para>If the 32-character <replaceable>ID</replaceable> is specified, it may optionally be followed
 302         by <replaceable>offset</replaceable> which identifies the boot relative to the one given by boot
 303         <replaceable>ID</replaceable>. Negative values mean earlier boots and positive values mean later
 304         boots. If <replaceable>offset</replaceable> is not specified, a value of zero is assumed, and the
 305         logs for the boot given by <replaceable>ID</replaceable> are shown.</para>
 306
 307         <para>The special argument <constant>all</constant> can be used to negate the effect of an earlier
 308         use of <option>-b</option>.</para>
 309
 310         <xi:include href="version-info.xml" xpointer="v186"/></listitem>
 311       </varlistentry>
 312
 313       <varlistentry>
 314         <term><option>-u</option></term>
 315         <term><option>--unit=<replaceable>UNIT</replaceable>|<replaceable>PATTERN</replaceable></option></term>
 316
 317         <listitem><para>Show messages for the specified systemd unit <replaceable>UNIT</replaceable> (such as
 318         a service unit), or for any of the units matched by <replaceable>PATTERN</replaceable>.  If a pattern
 319         is specified, a list of unit names found in the journal is compared with the specified pattern and
 320         all that match are used. For each unit name, a match is added for messages from the unit
 321         (<literal>_SYSTEMD_UNIT=<replaceable>UNIT</replaceable></literal>), along with additional matches for
 322         messages from systemd and messages about coredumps for the specified unit. A match is also added for
 323         <literal>_SYSTEMD_SLICE=<replaceable>UNIT</replaceable></literal>, such that if the provided
 324         <replaceable>UNIT</replaceable> is a
 325         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 326         unit, all logs of children of the slice will be shown.</para>
 327
 328         <para>With <option>--user</option>, all <option>--unit=</option> arguments will be converted to match
 329         user messages as if specified with <option>--user-unit=</option>.</para>
 330
 331         <para>This parameter can be specified multiple times.</para>
 332
 333         <xi:include href="version-info.xml" xpointer="v195"/></listitem>
 334       </varlistentry>
 335
 336       <varlistentry>
 337         <term><option>--user-unit=</option></term>
 338
 339         <listitem><para>Show messages for the specified user session unit. This will add a match for messages
 340         from the unit (<literal>_SYSTEMD_USER_UNIT=</literal> and <literal>_UID=</literal>) and additional
 341         matches for messages from session systemd and messages about coredumps for the specified unit. A
 342         match is also added for <literal>_SYSTEMD_USER_SLICE=<replaceable>UNIT</replaceable></literal>, such
 343         that if the provided <replaceable>UNIT</replaceable> is a
 344         <citerefentry><refentrytitle>systemd.slice</refentrytitle><manvolnum>5</manvolnum></citerefentry>
 345         unit, all logs of children of the unit will be shown.</para>
 346
 347         <para>This parameter can be specified multiple times.</para>
 348
 349         <xi:include href="version-info.xml" xpointer="v198"/></listitem>
 350       </varlistentry>
 351
 352       <varlistentry>
 353         <term><option>-t</option></term>
 354         <term><option>--identifier=<replaceable>SYSLOG_IDENTIFIER</replaceable></option></term>
 355
 356         <listitem><para>Show messages for the specified syslog identifier
 357         <replaceable>SYSLOG_IDENTIFIER</replaceable>.</para>
 358
 359         <para>This parameter can be specified multiple times.</para>
 360
 361         <xi:include href="version-info.xml" xpointer="v217"/></listitem>
 362       </varlistentry>
 363
 364       <varlistentry>
 365         <term><option>-p</option></term>
 366         <term><option>--priority=</option></term>
 367
 368         <listitem><para>Filter output by message priorities or priority ranges. Takes either a single numeric
 369         or textual log level (i.e. between 0/<literal>emerg</literal> and 7/<literal>debug</literal>), or a
 370         range of numeric/text log levels in the form FROM..TO. The log levels are the usual syslog log levels
 371         as documented in <citerefentry
 372         project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 373         i.e. <literal>emerg</literal> (0), <literal>alert</literal> (1), <literal>crit</literal> (2),
 374         <literal>err</literal> (3), <literal>warning</literal> (4), <literal>notice</literal> (5),
 375         <literal>info</literal> (6), <literal>debug</literal> (7). If a single log level is specified, all
 376         messages with this log level or a lower (hence more important) log level are shown. If a range is
 377         specified, all messages within the range are shown, including both the start and the end value of the
 378         range. This will add <literal>PRIORITY=</literal> matches for the specified
 379         priorities.</para>
 380
 381         <xi:include href="version-info.xml" xpointer="v188"/></listitem>
 382       </varlistentry>
 383
 384       <varlistentry>
 385         <term><option>--facility=</option></term>
 386
 387         <listitem><para>Filter output by syslog facility. Takes a comma-separated list of numbers or
 388         facility names. The names are the usual syslog facilities as documented in <citerefentry
 389         project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
 390         <option>--facility=help</option> may be used to display a list of known facility names and exit.
 391         </para>
 392
 393         <xi:include href="version-info.xml" xpointer="v245"/></listitem>
 394       </varlistentry>
 395
 396       <varlistentry>
 397         <term><option>-g</option></term>
 398         <term><option>--grep=</option></term>
 399
 400         <listitem><para>Filter output to entries where the <varname>MESSAGE=</varname> field matches the
 401         specified regular expression. PERL-compatible regular expressions are used, see <citerefentry
 402         project='url'><refentrytitle
 403         url='http://pcre.org/current/doc/html/pcre2pattern.html'>pcre2pattern</refentrytitle><manvolnum>3</manvolnum></citerefentry>
 404         for a detailed description of the syntax.</para>
 405
 406         <para>If the pattern is all lowercase, matching is case insensitive.  Otherwise, matching is case
 407         sensitive. This can be overridden with the <option>--case-sensitive</option> option, see
 408         below.</para>
 409
 410         <para>When used with <option>--lines=</option> (not prefixed with <literal>+</literal>),
 411         <option>--reverse</option> is implied.</para>
 412
 413         <xi:include href="version-info.xml" xpointer="v237"/></listitem>
 414       </varlistentry>
 415
 416       <varlistentry>
 417         <term><option>--case-sensitive<optional>=BOOLEAN</optional></option></term>
 418
 419         <listitem><para>Make pattern matching case sensitive or case insensitive.</para>
 420
 421         <xi:include href="version-info.xml" xpointer="v237"/></listitem>
 422       </varlistentry>
 423
 424       <varlistentry>
 425         <term><option>-k</option></term>
 426         <term><option>--dmesg</option></term>
 427
 428         <listitem><para>Show only kernel messages. This implies <option>-b</option> and adds the match
 429         <literal>_TRANSPORT=kernel</literal>.</para>
 430
 431         <xi:include href="version-info.xml" xpointer="v205"/></listitem>
 432       </varlistentry>
 433     </variablelist>
 434   </refsect1>
 435
 436   <refsect1>
 437     <title>Output Options</title>
 438
 439     <para>The following options control how journal records are printed:</para>
 440
 441     <variablelist>
 442       <varlistentry>
 443         <term><option>-o</option></term>
 444         <term><option>--output=</option></term>
 445
 446         <listitem><para>Controls the formatting of the journal entries that are shown. Takes one of the
 447         following options:</para>
 448
 449         <variablelist>
 450           <varlistentry>
 451             <term><option>short</option></term>
 452             <listitem><para>is the default and generates an output that is mostly identical to the
 453             formatting of classic syslog files, showing one line per journal entry.</para>
 454
 455             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 456           </varlistentry>
 457
 458           <varlistentry>
 459             <term><option>short-full</option></term>
 460             <listitem><para>is very similar, but shows timestamps in the format the
 461             <option>--since=</option> and <option>--until=</option> options accept. Unlike the timestamp
 462             information shown in <option>short</option> output mode this mode includes weekday, year and
 463             timezone information in the output, and is locale-independent.</para>
 464
 465             <xi:include href="version-info.xml" xpointer="v232"/></listitem>
 466           </varlistentry>
 467
 468           <varlistentry>
 469             <term><option>short-iso</option></term>
 470             <listitem><para>is very similar, but shows timestamps in the
 471             <ulink url="https://tools.ietf.org/html/rfc3339">RFC 3339</ulink> profile of ISO 8601.</para>
 472
 473             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 474           </varlistentry>
 475
 476           <varlistentry>
 477             <term><option>short-iso-precise</option></term>
 478             <listitem><para>as for <option>short-iso</option> but includes full microsecond
 479             precision.</para>
 480
 481             <xi:include href="version-info.xml" xpointer="v234"/></listitem>
 482           </varlistentry>
 483
 484           <varlistentry>
 485             <term><option>short-precise</option></term>
 486             <listitem><para>is very similar, but shows classic syslog timestamps with full microsecond
 487             precision.</para>
 488
 489             <xi:include href="version-info.xml" xpointer="v207"/></listitem>
 490           </varlistentry>
 491
 492           <varlistentry>
 493             <term><option>short-monotonic</option></term>
 494             <listitem><para>is very similar, but shows monotonic timestamps instead of wallclock
 495             timestamps.</para>
 496
 497             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 498           </varlistentry>
 499
 500           <varlistentry>
 501             <term><option>short-delta</option></term>
 502             <listitem><para>as for <option>short-monotonic</option> but includes the time difference
 503             to the previous entry.
 504             Maybe unreliable time differences are marked by a <literal>*</literal>.</para>
 505
 506             <xi:include href="version-info.xml" xpointer="v252"/></listitem>
 507           </varlistentry>
 508
 509           <varlistentry>
 510             <term><option>short-unix</option></term>
 511             <listitem><para>is very similar, but shows seconds passed since January 1st 1970 UTC instead of
 512             wallclock timestamps ("UNIX time"). The time is shown with microsecond accuracy.</para>
 513
 514             <xi:include href="version-info.xml" xpointer="v230"/></listitem>
 515           </varlistentry>
 516
 517           <varlistentry>
 518             <term><option>verbose</option></term>
 519             <listitem><para>shows the full-structured entry items with all fields.</para>
 520
 521             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 522           </varlistentry>
 523
 524           <varlistentry>
 525             <term><option>export</option></term>
 526             <listitem><para>serializes the journal into a binary (but mostly text-based) stream suitable
 527             for backups and network transfer (see <ulink
 528             url="https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-export-format">Journal Export
 529             Format</ulink> for more information). To import the binary stream back into native journald
 530             format use
 531             <citerefentry><refentrytitle>systemd-journal-remote</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
 532
 533             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 534           </varlistentry>
 535
 536           <varlistentry>
 537             <term><option>json</option></term>
 538             <listitem><para>formats entries as JSON objects, separated by newline characters (see <ulink
 539             url="https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-json-format">Journal JSON Format</ulink>
 540             for more information). Field values are generally encoded as JSON strings, with three exceptions:
 541             <orderedlist>
 542               <listitem><para>Fields larger than 4096 bytes are encoded as <constant>null</constant>
 543               values. (This may be turned off by passing <option>--all</option>, but be aware that this may
 544               allocate overly long JSON objects.)</para></listitem>
 545
 546               <listitem><para>Journal entries permit non-unique fields within the same log entry. JSON does
 547               not allow non-unique fields within objects. Due to this, if a non-unique field is encountered a
 548               JSON array is used as field value, listing all field values as elements.</para></listitem>
 549
 550               <listitem><para>Fields containing non-printable or non-UTF8 bytes are encoded as arrays
 551               containing the raw bytes individually formatted as unsigned numbers.</para></listitem>
 552             </orderedlist>
 553
 554             Note that this encoding is reversible (with the exception of the size limit).</para>
 555
 556             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 557           </varlistentry>
 558
 559           <varlistentry>
 560             <term><option>json-pretty</option></term>
 561             <listitem><para>formats entries as JSON data structures, but formats them in multiple lines in
 562             order to make them more readable by humans.</para>
 563
 564             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 565           </varlistentry>
 566
 567           <varlistentry>
 568             <term><option>json-sse</option></term>
 569             <listitem><para>formats entries as JSON data structures, but wraps them in a format suitable for
 570             <ulink
 571             url="https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events">Server-Sent
 572             Events</ulink>.</para>
 573
 574             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 575           </varlistentry>
 576
 577           <varlistentry>
 578             <term><option>json-seq</option></term>
 579             <listitem><para>formats entries as JSON data structures, but prefixes them with an ASCII Record
 580             Separator character (0x1E) and suffixes them with an ASCII Line Feed character (0x0A), in
 581             accordance with <ulink url="https://tools.ietf.org/html/rfc7464">JavaScript Object Notation
 582             (JSON) Text Sequences </ulink> (<literal>application/json-seq</literal>).</para>
 583
 584             <xi:include href="version-info.xml" xpointer="v240"/></listitem>
 585           </varlistentry>
 586
 587           <varlistentry>
 588             <term><option>cat</option></term>
 589             <listitem><para>generates a very terse output, only showing the actual message of each journal
 590             entry with no metadata, not even a timestamp. If combined with the
 591             <option>--output-fields=</option> option will output the listed fields for each log record,
 592             instead of the message.</para>
 593
 594             <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 595           </varlistentry>
 596
 597           <varlistentry>
 598             <term><option>with-unit</option></term>
 599             <listitem><para>similar to <option>short-full</option>, but prefixes the unit and user unit names
 600             instead of the traditional syslog identifier. Useful when using templated instances, as it will
 601             include the arguments in the unit names.</para>
 602
 603             <xi:include href="version-info.xml" xpointer="v239"/></listitem>
 604           </varlistentry>
 605         </variablelist></listitem>
 606       </varlistentry>
 607
 608       <varlistentry>
 609         <term><option>--truncate-newline</option></term>
 610
 611         <listitem><para>Truncate each log message at the first newline character on output, so that only the
 612         first line of each message is displayed.</para>
 613
 614         <xi:include href="version-info.xml" xpointer="v254"/></listitem>
 615       </varlistentry>
 616
 617       <varlistentry>
 618         <term><option>--output-fields=</option></term>
 619
 620         <listitem><para>A comma separated list of the fields which should be included in the output. This
 621         has an effect only for the output modes which would normally show all fields
 622         (<option>verbose</option>, <option>export</option>, <option>json</option>,
 623         <option>json-pretty</option>, <option>json-sse</option> and <option>json-seq</option>), as well as
 624         on <option>cat</option>. For the former, the <literal>__CURSOR</literal>,
 625         <literal>__REALTIME_TIMESTAMP</literal>, <literal>__MONOTONIC_TIMESTAMP</literal>, and
 626         <literal>_BOOT_ID</literal> fields are always printed.</para>
 627
 628         <xi:include href="version-info.xml" xpointer="v236"/></listitem>
 629       </varlistentry>
 630
 631       <varlistentry>
 632         <term><option>-n</option></term>
 633         <term><option>--lines=</option></term>
 634
 635         <listitem><para>Show the most recent journal events and limit the number of events shown. The argument
 636         is a positive integer or <literal>all</literal> to disable the limit. Additionally, if the number is
 637         prefixed with <literal>+</literal>, the oldest journal events are used instead. The default value is
 638         10 if no argument is given.</para>
 639
 640         <para>If <option>--follow</option> is used, this option is implied. When not prefixed with <literal>+</literal>
 641         and used with <option>--grep=</option>, <option>--reverse</option> is implied.</para></listitem>
 642       </varlistentry>
 643
 644       <varlistentry>
 645         <term><option>-r</option></term>
 646         <term><option>--reverse</option></term>
 647
 648         <listitem><para>Reverse output so that the newest entries are displayed first.</para>
 649
 650         <xi:include href="version-info.xml" xpointer="v198"/></listitem>
 651       </varlistentry>
 652
 653       <varlistentry>
 654         <term><option>--show-cursor</option></term>
 655
 656         <listitem><para>The cursor is shown after the last entry after two dashes:</para>
 657         <programlisting>-- cursor: s=0639…</programlisting>
 658         <para>The format of the cursor is private and subject to change.</para>
 659
 660         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 661       </varlistentry>
 662
 663       <varlistentry>
 664         <term><option>--utc</option></term>
 665
 666         <listitem><para>Express time in Coordinated Universal Time (UTC).</para>
 667
 668         <xi:include href="version-info.xml" xpointer="v217"/></listitem>
 669       </varlistentry>
 670
 671       <varlistentry>
 672         <term><option>-x</option></term>
 673         <term><option>--catalog</option></term>
 674
 675         <listitem><para>Augment log lines with explanation texts from the message catalog. This will add
 676         explanatory help texts to log messages in the output where this is available. These short help texts
 677         will explain the context of an error or log event, possible solutions, as well as pointers to support
 678         forums, developer documentation, and any other relevant manuals. Note that help texts are not
 679         available for all messages, but only for selected ones. For more information on the message catalog,
 680         please refer to the <ulink url="https://www.freedesktop.org/wiki/Software/systemd/catalog">Message
 681         Catalog Developer Documentation</ulink>.</para>
 682
 683         <para>Note: when attaching <command>journalctl</command> output to bug reports, please do
 684         <emphasis>not</emphasis> use <option>-x</option>.</para>
 685
 686         <xi:include href="version-info.xml" xpointer="v196"/></listitem>
 687       </varlistentry>
 688
 689       <varlistentry>
 690         <term><option>--no-hostname</option></term>
 691
 692         <listitem><para>Don't show the hostname field of log messages originating from the local host. This
 693         switch has an effect only on the <option>short</option> family of output modes (see above).</para>
 694
 695         <para>Note: this option does not remove occurrences of the hostname from log entries themselves, so
 696         it does not prevent the hostname from being visible in the logs.</para>
 697
 698         <xi:include href="version-info.xml" xpointer="v230"/></listitem>
 699       </varlistentry>
 700
 701       <varlistentry>
 702         <term><option>--no-full</option></term>
 703         <term><option>--full</option></term>
 704         <term><option>-l</option></term>
 705
 706         <listitem><para>Ellipsize fields when they do not fit in available columns.  The default is to show
 707         full fields, allowing them to wrap or be truncated by the pager, if one is used.</para>
 708
 709         <para>The old options <option>-l</option>/<option>--full</option> are not useful anymore, except to
 710         undo <option>--no-full</option>.</para>
 711
 712         <xi:include href="version-info.xml" xpointer="v196"/></listitem>
 713       </varlistentry>
 714
 715       <varlistentry>
 716         <term><option>-a</option></term>
 717         <term><option>--all</option></term>
 718
 719         <listitem><para>Show all fields in full, even if they include unprintable characters or are very
 720         long. By default, fields with unprintable characters are abbreviated as "blob data". (Note that the
 721         pager may escape unprintable characters again.)</para></listitem>
 722       </varlistentry>
 723
 724       <varlistentry>
 725         <term><option>-f</option></term>
 726         <term><option>--follow</option></term>
 727
 728         <listitem><para>Show only the most recent journal entries, and continuously print new entries as
 729         they are appended to the journal.</para></listitem>
 730       </varlistentry>
 731
 732       <varlistentry>
 733         <term><option>--no-tail</option></term>
 734
 735         <listitem><para>Show all stored output lines, even in follow mode. Undoes the effect of
 736         <option>--lines=</option>.</para></listitem>
 737       </varlistentry>
 738
 739       <varlistentry>
 740         <term><option>-q</option></term>
 741         <term><option>--quiet</option></term>
 742
 743         <listitem><para>Suppresses all informational messages (i.e. "-- Journal begins at …", "-- Reboot
 744         --"), any warning messages regarding inaccessible system journals when run as a normal
 745         user.</para></listitem>
 746       </varlistentry>
 747     </variablelist>
 748   </refsect1>
 749
 750   <refsect1>
 751     <title>Pager Control Options</title>
 752
 753     <para>The following options control page support:</para>
 754
 755     <variablelist>
 756
 757       <xi:include href="standard-options.xml" xpointer="no-pager" />
 758
 759       <varlistentry>
 760         <term><option>-e</option></term>
 761         <term><option>--pager-end</option></term>
 762
 763         <listitem><para>Immediately jump to the end of the journal inside the implied pager tool. This
 764         implies <option>-n1000</option> to guarantee that the pager will not buffer logs of unbounded
 765         size. This may be overridden with an explicit <option>-n</option> with some other numeric value,
 766         while <option>-nall</option> will disable this cap.  Note that this option is only supported for
 767         the <citerefentry
 768         project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
 769         pager.</para>
 770
 771         <xi:include href="version-info.xml" xpointer="v198"/></listitem>
 772       </varlistentry>
 773     </variablelist>
 774   </refsect1>
 775
 776   <refsect1>
 777     <title>Forward Secure Sealing (FSS) Options</title>
 778
 779     <para>The following options may be used together with the <option>--setup-keys</option> command described
 780     below:</para>
 781
 782     <variablelist>
 783       <varlistentry>
 784         <term><option>--interval=</option></term>
 785
 786         <listitem><para>Specifies the change interval for the sealing key when generating an FSS key pair
 787         with <option>--setup-keys</option>. Shorter intervals increase CPU consumption but shorten the time
 788         range of undetectable journal alterations. Defaults to 15min.</para>
 789
 790         <xi:include href="version-info.xml" xpointer="v189"/></listitem>
 791       </varlistentry>
 792
 793       <varlistentry>
 794         <term><option>--verify-key=</option></term>
 795
 796         <listitem><para>Specifies the FSS verification key to use for the <option>--verify</option>
 797         operation.</para>
 798
 799         <xi:include href="version-info.xml" xpointer="v189"/></listitem>
 800       </varlistentry>
 801
 802       <varlistentry>
 803         <term><option>--force</option></term>
 804
 805         <listitem><para>When <option>--setup-keys</option> is passed and Forward Secure Sealing (FSS) has
 806         already been configured, recreate FSS keys.</para>
 807
 808         <xi:include href="version-info.xml" xpointer="v206"/></listitem>
 809       </varlistentry>
 810     </variablelist>
 811   </refsect1>
 812
 813   <refsect1>
 814     <title>Commands</title>
 815
 816     <para>The following commands are understood. If none is specified the default is to display journal records.</para>
 817
 818     <variablelist>
 819       <varlistentry>
 820         <term><option>-N</option></term>
 821         <term><option>--fields</option></term>
 822
 823         <listitem><para>Print all field names currently used in all entries of the journal.</para>
 824
 825         <xi:include href="version-info.xml" xpointer="v229"/></listitem>
 826       </varlistentry>
 827
 828       <varlistentry>
 829         <term><option>-F</option></term>
 830         <term><option>--field=</option></term>
 831
 832         <listitem><para>Print all possible data values the specified field can take in all entries of the
 833         journal.</para>
 834
 835         <xi:include href="version-info.xml" xpointer="v195"/></listitem>
 836       </varlistentry>
 837
 838       <varlistentry>
 839         <term><option>--list-boots</option></term>
 840
 841         <listitem><para>Show a tabular list of boot numbers (relative to the current boot), their IDs, and
 842         the timestamps of the first and last message pertaining to the boot.</para>
 843
 844         <xi:include href="version-info.xml" xpointer="v209"/></listitem>
 845       </varlistentry>
 846
 847       <varlistentry>
 848         <term><option>--disk-usage</option></term>
 849
 850         <listitem><para>Shows the current disk usage of all journal files. This shows the sum of the disk
 851         usage of all archived and active journal files.</para>
 852
 853         <xi:include href="version-info.xml" xpointer="v190"/></listitem>
 854       </varlistentry>
 855
 856       <varlistentry>
 857         <term><option>--vacuum-size=</option></term>
 858         <term><option>--vacuum-time=</option></term>
 859         <term><option>--vacuum-files=</option></term>
 860
 861         <listitem><para><option>--vacuum-size=</option> removes the oldest archived journal files until the
 862         disk space they use falls below the specified size. Accepts the usual <literal>K</literal>,
 863         <literal>M</literal>, <literal>G</literal> and <literal>T</literal> suffixes (to the base of
 864         1024).</para>
 865
 866         <para><option>--vacuum-time=</option> removes archived journal files older than the specified
 867         timespan. Accepts the usual <literal>s</literal> (default), <literal>m</literal>,
 868         <literal>h</literal>, <literal>days</literal>, <literal>months</literal>, <literal>weeks</literal>
 869         and <literal>years</literal> suffixes, see
 870         <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
 871         details.</para>
 872
 873         <para><option>--vacuum-files=</option> leaves only the specified number of separate journal
 874         files.</para>
 875
 876         <para>Note that running <option>--vacuum-size=</option> has only an indirect effect on the output
 877         shown by <option>--disk-usage</option>, as the latter includes active journal files, while the
 878         vacuuming operation only operates on archived journal files. Similarly,
 879         <option>--vacuum-files=</option> might not actually reduce the number of journal files to below the
 880         specified number, as it will not remove active journal files.</para>
 881
 882         <para><option>--vacuum-size=</option>, <option>--vacuum-time=</option> and
 883         <option>--vacuum-files=</option> may be combined in a single invocation to enforce any combination of
 884         a size, a time and a number of files limit on the archived journal files. Specifying any of these
 885         three parameters as zero is equivalent to not enforcing the specific limit, and is thus
 886         redundant.</para>
 887
 888         <para>These three switches may also be combined with <option>--rotate</option> into one command. If
 889         so, all active files are rotated first, and the requested vacuuming operation is executed right
 890         after. The rotation has the effect that all currently active files are archived (and potentially new,
 891         empty journal files opened as replacement), and hence the vacuuming operation has the greatest effect
 892         as it can take all log data written so far into account.</para>
 893
 894         <xi:include href="version-info.xml" xpointer="v218"/></listitem>
 895       </varlistentry>
 896
 897       <varlistentry>
 898         <term><option>--verify</option></term>
 899
 900         <listitem><para>Check the journal file for internal consistency. If the file has been generated
 901         with FSS enabled and the FSS verification key has been specified with
 902         <option>--verify-key=</option>, authenticity of the journal file is verified.</para>
 903
 904         <xi:include href="version-info.xml" xpointer="v189"/></listitem>
 905       </varlistentry>
 906
 907       <varlistentry>
 908         <term><option>--sync</option></term>
 909
 910         <listitem><para>Asks the journal daemon to write all yet unwritten journal data to the backing file
 911         system and synchronize all journals. This call does not return until the synchronization operation
 912         is complete. This command guarantees that any log messages written before its invocation are safely
 913         stored on disk at the time it returns.</para>
 914
 915         <xi:include href="version-info.xml" xpointer="v228"/></listitem>
 916       </varlistentry>
 917
 918       <varlistentry>
 919         <term><option>--relinquish-var</option></term>
 920
 921         <listitem><para>Asks the journal daemon for the reverse operation to <option>--flush</option>: if
 922         requested the daemon will write further log data to <filename>/run/log/journal/</filename> and
 923         stops writing to <filename>/var/log/journal/</filename>. A subsequent call to
 924         <option>--flush</option> causes the log output to switch back to
 925         <filename>/var/log/journal/</filename>, see above.</para>
 926
 927         <xi:include href="version-info.xml" xpointer="v243"/></listitem>
 928       </varlistentry>
 929
 930       <varlistentry>
 931         <term><option>--smart-relinquish-var</option></term>
 932
 933         <listitem><para>Similar to <option>--relinquish-var</option>, but executes no operation if the root
 934         file system and <filename>/var/log/journal/</filename> reside on the same mount point. This operation
 935         is used during system shutdown in order to make the journal daemon stop writing data to
 936         <filename>/var/log/journal/</filename> in case that directory is located on a mount point that needs
 937         to be unmounted.</para>
 938
 939         <xi:include href="version-info.xml" xpointer="v243"/></listitem>
 940       </varlistentry>
 941
 942       <varlistentry>
 943         <term><option>--flush</option></term>
 944
 945         <listitem><para>Asks the journal daemon to flush any log data stored in
 946         <filename>/run/log/journal/</filename> into <filename>/var/log/journal/</filename>, if persistent
 947         storage is enabled. This call does not return until the operation is complete. Note that this call is
 948         idempotent: the data is only flushed from <filename>/run/log/journal/</filename> into
 949         <filename>/var/log/journal/</filename> once during system runtime (but see
 950         <option>--relinquish-var</option> below), and this command exits cleanly without executing any
 951         operation if this has already happened. This command effectively guarantees that all data is flushed
 952         to <filename>/var/log/journal/</filename> at the time it returns.</para>
 953
 954         <xi:include href="version-info.xml" xpointer="v217"/></listitem>
 955       </varlistentry>
 956
 957       <varlistentry>
 958         <term><option>--rotate</option></term>
 959
 960         <listitem><para>Asks the journal daemon to rotate journal files. This call does not return until
 961         the rotation operation is complete. Journal file rotation has the effect that all currently active
 962         journal files are marked as archived and renamed, so that they are never written to in future. New
 963         (empty) journal files are then created in their place. This operation may be combined with
 964         <option>--vacuum-size=</option>, <option>--vacuum-time=</option> and
 965         <option>--vacuum-file=</option> into a single command, see above.</para>
 966
 967         <xi:include href="version-info.xml" xpointer="v227"/></listitem>
 968       </varlistentry>
 969
 970       <varlistentry>
 971         <term><option>--header</option></term>
 972
 973         <listitem><para>Instead of showing journal contents, show internal header information of the
 974         journal fields accessed.</para>
 975
 976         <para>This option is particularly useful when trying to identify out-of-order journal entries, as
 977         happens for example when the machine is booted with the wrong system time.</para>
 978
 979         <xi:include href="version-info.xml" xpointer="v187"/></listitem>
 980       </varlistentry>
 981
 982       <varlistentry>
 983         <term><option>--list-catalog <optional><replaceable>128-bit-ID…</replaceable></optional></option></term>
 984
 985         <listitem><para>List the contents of the message catalog as a table of message IDs, plus their
 986         short description strings.</para>
 987
 988         <para>If any <replaceable>128-bit-ID</replaceable>s are specified, only those entries are
 989         shown.</para>
 990
 991         <xi:include href="version-info.xml" xpointer="v196"/></listitem>
 992       </varlistentry>
 993
 994       <varlistentry>
 995         <term><option>--dump-catalog <optional><replaceable>128-bit-ID…</replaceable></optional></option></term>
 996
 997         <listitem><para>Show the contents of the message catalog, with entries separated by a line
 998         consisting of two dashes and the ID (the format is the same as <filename>.catalog</filename>
 999         files).</para>
1000
1001         <para>If any <replaceable>128-bit-ID</replaceable>s are specified, only those entries are
1002         shown.</para>
1003
1004         <xi:include href="version-info.xml" xpointer="v199"/></listitem>
1005       </varlistentry>
1006
1007       <varlistentry>
1008         <term><option>--update-catalog</option></term>
1009
1010         <listitem><para>Update the message catalog index. This command needs to be executed each time new
1011         catalog files are installed, removed, or updated to rebuild the binary catalog
1012         index.</para>
1013
1014         <xi:include href="version-info.xml" xpointer="v196"/></listitem>
1015       </varlistentry>
1016
1017       <varlistentry>
1018         <term><option>--setup-keys</option></term>
1019
1020         <listitem><para>Instead of showing journal contents, generate a new key pair for Forward Secure
1021         Sealing (FSS). This will generate a sealing key and a verification key. The sealing key is stored in
1022         the journal data directory and shall remain on the host. The verification key should be stored
1023         externally. Refer to the <option>Seal=</option> option in
1024         <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry> for
1025         information on Forward Secure Sealing and for a link to a refereed scholarly paper detailing the
1026         cryptographic theory it is based on.</para>
1027
1028         <xi:include href="version-info.xml" xpointer="v189"/></listitem>
1029       </varlistentry>
1030
1031       <xi:include href="standard-options.xml" xpointer="help" />
1032       <xi:include href="standard-options.xml" xpointer="version" />
1033     </variablelist>
1034   </refsect1>
1035
1036   <refsect1>
1037     <title>Exit status</title>
1038
1039     <para>On success, 0 is returned; otherwise, a non-zero failure code is returned.</para>
1040   </refsect1>
1041
1042   <xi:include href="common-variables.xml" />
1043
1044   <refsect1>
1045     <title>Examples</title>
1046
1047     <para>Without arguments, all collected logs are shown unfiltered:</para>
1048
1049     <programlisting>journalctl</programlisting>
1050
1051     <para>With one match specified, all entries with a field matching the expression are shown:</para>
1052
1053     <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service
1054 journalctl _SYSTEMD_CGROUP=/user.slice/user-42.slice/session-c1.scope</programlisting>
1055
1056     <para>If two different fields are matched, only entries matching both expressions at the same time are
1057     shown:</para>
1058
1059     <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097</programlisting>
1060
1061     <para>If two matches refer to the same field, all entries matching either expression are shown:</para>
1062
1063     <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service</programlisting>
1064
1065     <para>If the separator <literal>+</literal> is used, two expressions may be combined in a logical OR. The
1066     following will show all messages from the Avahi service process with the PID 28097 plus all messages from
1067     the D-Bus service (from any of its processes):</para>
1068
1069     <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097 + _SYSTEMD_UNIT=dbus.service</programlisting>
1070
1071     <para>To show all fields emitted <emphasis>by</emphasis> a unit and <emphasis>about</emphasis> the unit,
1072     option <option>-u</option>/<option>--unit=</option> should be used. <command>journalctl -u
1073     <replaceable>name</replaceable></command> expands to a complex filter similar to
1074
1075     <programlisting>_SYSTEMD_UNIT=<replaceable>name</replaceable>.service
1076   + UNIT=<replaceable>name</replaceable>.service _PID=1
1077   + OBJECT_SYSTEMD_UNIT=<replaceable>name</replaceable>.service _UID=0
1078   + COREDUMP_UNIT=<replaceable>name</replaceable>.service _UID=0 MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1</programlisting>
1079
1080     (see
1081     <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
1082     for an explanation of those patterns).</para>
1083
1084     <para>Show all logs generated by the D-Bus executable:</para>
1085
1086     <programlisting>journalctl /usr/bin/dbus-daemon</programlisting>
1087
1088     <para>Show all kernel logs from previous boot:</para>
1089
1090     <programlisting>journalctl -k -b -1</programlisting>
1091
1092     <para>Show a live log display from a system service <filename>apache.service</filename>:</para>
1093
1094     <programlisting>journalctl -f -u apache</programlisting>
1095   </refsect1>
1096
1097   <refsect1>
1098     <title>See Also</title>
1099     <para>
1100       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1101       <citerefentry><refentrytitle>systemd-cat</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1102       <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1103       <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1104       <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
1105       <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1106       <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
1107       <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
1108       <citerefentry><refentrytitle>systemd-journal-remote.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
1109       <citerefentry><refentrytitle>systemd-journal-upload.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
1110     </para>
1111   </refsect1>
1112 </refentry>