[thirdparty/systemd.git] / man / journalctl.xml

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  <refentry id="journalctl"
            xmlns:xi="http://www.w3.org/2001/XInclude">

    <refentryinfo>
      <title>journalctl</title>
      <productname>systemd</productname>
    </refentryinfo>

    <refmeta>
      <refentrytitle>journalctl</refentrytitle>
      <manvolnum>1</manvolnum>
    </refmeta>

    <refnamediv>
      <refname>journalctl</refname>
      <refpurpose>Query the systemd journal</refpurpose>
    </refnamediv>

    <refsynopsisdiv>
      <cmdsynopsis>
        <command>journalctl</command>
        <arg choice="opt" rep="repeat">OPTIONS</arg>
        <arg choice="opt" rep="repeat">MATCHES</arg>
      </cmdsynopsis>
    </refsynopsisdiv>

    <refsect1>
      <title>Description</title>

      <para><command>journalctl</command> may be used to query the
      contents of the
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
      journal as written by
      <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>

      <para>If called without parameters, it will show the full
      contents of the journal, starting with the oldest entry
      collected.</para>

      <para>If one or more match arguments are passed, the output is
      filtered accordingly. A match is in the format
      <literal>FIELD=VALUE</literal>,
      e.g. <literal>_SYSTEMD_UNIT=httpd.service</literal>, referring
      to the components of a structured journal entry. See
      <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>
      for a list of well-known fields. If multiple matches are
      specified matching different fields, the log entries are
      filtered by both, i.e. the resulting output will show only
      entries matching all the specified matches of this kind. If two
      matches apply to the same field, then they are automatically
      matched as alternatives, i.e. the resulting output will show
      entries matching any of the specified matches for the same
      field. Finally, the character <literal>+</literal> may appear
      as a separate word between other terms on the command line. This
      causes all matches before and after to be combined in a
      disjunction (i.e. logical OR).</para>

      <para>It is also possible to filter the entries by specifying an
      absolute file path as an argument. The file path may be a file or
      a symbolic link and the file must exist at the time of the query. If a
      file path refers to an executable binary, an <literal>_EXE=</literal>
      match for the canonicalized binary path is added to the query. If a
      file path refers to an executable script, a <literal>_COMM=</literal>
      match for the script name is added to the query. If a file path
      refers to a device node, <literal>_KERNEL_DEVICE=</literal> matches for
      the kernel name of the device and for each of its ancestor devices is
      added to the query. Symbolic links are dereferenced, kernel names are
      synthesized, and parent devices are identified from the environment at
      the time of the query. In general, a device node is the best proxy for
      an actual device, as log entries do not usually contain fields that
      identify an actual device. For the resulting log entries to be correct
      for the actual device, the relevant parts of the environment at the time
      the entry was logged, in particular the actual device corresponding to
      the device node, must have been the same as those at the time of the
      query. Because device nodes generally change their corresponding devices
      across reboots, specifying a device node path causes the resulting
      entries to be restricted to those from the current boot.</para>

      <para>Additional constraints may be added using options
      <option>--boot</option>, <option>--unit=</option>, etc., to
      further limit what entries will be shown (logical AND).</para>

      <para>Output is interleaved from all accessible journal files,
      whether they are rotated or currently being written, and
      regardless of whether they belong to the system itself or are
      accessible user journals.</para>

      <para>The set of journal files which will be used can be
      modified using the <option>--user</option>,
      <option>--system</option>, <option>--directory</option>, and
      <option>--file</option> options, see below.</para>

      <para>All users are granted access to their private per-user
      journals. However, by default, only root and users who are
      members of a few special groups are granted access to the system
      journal and the journals of other users. Members of the groups
      <literal>systemd-journal</literal>, <literal>adm</literal>, and
      <literal>wheel</literal> can read all journal files. Note
      that the two latter groups traditionally have additional
      privileges specified by the distribution. Members of the
      <literal>wheel</literal> group can often perform administrative
      tasks.</para>

      <para>The output is paged through <command>less</command> by
      default, and long lines are "truncated" to screen width. The
      hidden part can be viewed by using the left-arrow and
      right-arrow keys. Paging can be disabled; see the
      <option>--no-pager</option> option and the "Environment" section
      below.</para>

      <para>When outputting to a tty, lines are colored according to
      priority: lines of level ERROR and higher are colored red; lines
      of level NOTICE and higher are highlighted; other lines are
      displayed normally.</para>
    </refsect1>

    <refsect1>
      <title>Options</title>

      <para>The following options are understood:</para>

      <variablelist>
        <varlistentry>
          <term><option>--no-full</option></term>
          <term><option>--full</option></term>
          <term><option>-l</option></term>

          <listitem><para>Ellipsize fields when they do not fit in
          available columns.  The default is to show full fields,
          allowing them to wrap or be truncated by the pager, if one
          is used.</para>

          <para>The old options
          <option>-l</option>/<option>--full</option> are not useful
          anymore, except to undo <option>--no-full</option>.</para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-a</option></term>
          <term><option>--all</option></term>

          <listitem><para>Show all fields in full, even if they include unprintable characters or are very long. By
          default, fields with unprintable characters are abbreviated as "blob data". (Note that the pager may escape
          unprintable characters again.)</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-f</option></term>
          <term><option>--follow</option></term>

          <listitem><para>Show only the most recent journal entries,
          and continuously print new entries as they are appended to
          the journal.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-e</option></term>
          <term><option>--pager-end</option></term>

          <listitem><para>Immediately jump to the end of the journal
          inside the implied pager tool. This implies
          <option>-n1000</option> to guarantee that the pager will not
          buffer logs of unbounded size. This may be overridden with
          an explicit <option>-n</option> with some other numeric
          value, while <option>-nall</option> will disable this cap.
          Note that this option is only supported for the
          <citerefentry project='man-pages'><refentrytitle>less</refentrytitle><manvolnum>1</manvolnum></citerefentry>
          pager.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-n</option></term>
          <term><option>--lines=</option></term>

          <listitem><para>Show the most recent journal events and
          limit the number of events shown. If
          <option>--follow</option> is used, this option is
          implied. The argument is a positive integer or
          <literal>all</literal> to disable line limiting. The default
          value is 10 if no argument is given.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>--no-tail</option></term>

          <listitem><para>Show all stored output lines, even in follow
          mode. Undoes the effect of <option>--lines=</option>.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-r</option></term>
          <term><option>--reverse</option></term>

          <listitem><para>Reverse output so that the newest entries
          are displayed first.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><option>-o</option></term>
          <term><option>--output=</option></term>

          <listitem><para>Controls the formatting of the journal
          entries that are shown. Takes one of the following
          options:</para>
          <variablelist>
            <varlistentry>
              <term>
                <option>short</option>
              </term>
              <listitem>
                <para>is the default and generates an output that is
                mostly identical to the formatting of classic syslog
                files, showing one line per journal entry.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-full</option>
              </term>
              <listitem>
                <para>is very similar, but shows timestamps in the format the <option>--since=</option> and
                <option>--until=</option> options accept. Unlike the timestamp information shown in
                <option>short</option> output mode this mode includes weekday, year and timezone information in the
                output, and is locale-independent.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-iso</option>
              </term>
              <listitem>
                <para>is very similar, but shows ISO 8601 wallclock
                timestamps.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-iso-precise</option>
              </term>
              <listitem>
                <para>as for <option>short-iso</option> but includes full
                microsecond precision.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-precise</option>
              </term>
              <listitem>
                <para>is very similar, but shows classic syslog timestamps
                with full microsecond precision.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-monotonic</option>
              </term>
              <listitem>
                <para>is very similar, but shows monotonic timestamps
                instead of wallclock timestamps.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>short-unix</option>
              </term>
              <listitem>
                <para>is very similar, but shows seconds passed since January 1st 1970 UTC instead of wallclock
                timestamps ("UNIX time"). The time is shown with microsecond accuracy.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>verbose</option>
              </term>
              <listitem>
                <para>shows the full-structured entry items with all
                fields.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>export</option>
              </term>
              <listitem>
                <para>serializes the journal into a binary (but mostly
                text-based) stream suitable for backups and network
                transfer (see
                <ulink url="https://www.freedesktop.org/wiki/Software/systemd/export">Journal Export Format</ulink>
                for more information). To import the binary stream back
                into native journald format use
                <citerefentry><refentrytitle>systemd-journal-remote</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>json</option>
              </term>
              <listitem>
                <para>formats entries as JSON objects, separated by newline characters (see <ulink
                url="https://www.freedesktop.org/wiki/Software/systemd/json">Journal JSON Format</ulink> for more
                information). Field values are generally encoded as JSON strings, with three exceptions:
                <orderedlist>
                  <listitem><para>Fields larger than 4096 bytes are encoded as <constant>null</constant> values. (This
                  may be turned off by passing <option>--all</option>, but be aware that this may allocate overly long
                  JSON objects.) </para></listitem>

                  <listitem><para>Journal entries permit non-unique fields within the same log entry. JSON does not allow
                  non-unique fields within objects. Due to this, if a non-unique field is encountered a JSON array is
                  used as field value, listing all field values as elements.</para></listitem>

                  <listitem><para>Fields containing non-printable or non-UTF8 bytes are encoded as arrays containing
                  the raw bytes individually formatted as unsigned numbers.</para></listitem>
                </orderedlist>

                Note that this encoding is reversible (with the exception of the size limit).</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>json-pretty</option>
              </term>
              <listitem>
                <para>formats entries as JSON data structures, but
                formats them in multiple lines in order to make them
                more readable by humans.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>json-sse</option>
              </term>
              <listitem>
                <para>formats entries as JSON data structures, but wraps
                them in a format suitable for
                <ulink url="https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events">Server-Sent Events</ulink>.
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>json-seq</option>
              </term>
              <listitem>
                <para>formats entries as JSON data structures, but prefixes them with an ASCII Record Separator
                character (0x1E) and suffixes them with an ASCII Line Feed character (0x0A), in accordance with <ulink
                url="https://tools.ietf.org/html/rfc7464">JavaScript Object Notation (JSON) Text Sequences </ulink>
                (<literal>application/json-seq</literal>).
                </para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>cat</option>
              </term>
              <listitem>
                <para>generates a very terse output, only showing the
                actual message of each journal entry with no metadata,
                not even a timestamp.</para>
              </listitem>
            </varlistentry>

            <varlistentry>
              <term>
                <option>with-unit</option>
              </term>
              <listitem>
                <para>similar to short-full, but prefixes the unit and
                user unit names instead of the traditional syslog
                identifier. Useful when using templated instances, as it
                will include the arguments in the unit names.</para>
              </listitem>
            </varlistentry>
          </variablelist>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--output-fields=</option></term>

        <listitem><para>A comma separated list of the fields which should be included in the output. This only has an
        effect for the output modes which would normally show all fields (<option>verbose</option>,
        <option>export</option>, <option>json</option>, <option>json-pretty</option>, <option>json-sse</option> and
        <option>json-seq</option>). The <literal>__CURSOR</literal>, <literal>__REALTIME_TIMESTAMP</literal>,
        <literal>__MONOTONIC_TIMESTAMP</literal>, and <literal>_BOOT_ID</literal> fields are always
        printed.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--utc</option></term>

        <listitem><para>Express time in Coordinated Universal Time
        (UTC).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--no-hostname</option></term>

        <listitem><para>Don't show the hostname field of log messages originating from the local host. This switch only
        has an effect on the <option>short</option> family of output modes (see above).</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-x</option></term>
        <term><option>--catalog</option></term>

        <listitem><para>Augment log lines with explanation texts from
        the message catalog. This will add explanatory help texts to
        log messages in the output where this is available. These
        short help texts will explain the context of an error or log
        event, possible solutions, as well as pointers to support
        forums, developer documentation, and any other relevant
        manuals. Note that help texts are not available for all
        messages, but only for selected ones. For more information on
        the message catalog, please refer to the
        <ulink url="https://www.freedesktop.org/wiki/Software/systemd/catalog">Message Catalog Developer Documentation</ulink>.</para>

        <para>Note: when attaching <command>journalctl</command>
        output to bug reports, please do <emphasis>not</emphasis> use
        <option>-x</option>.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-q</option></term>
        <term><option>--quiet</option></term>

        <listitem><para>Suppresses all informational messages
        (i.e. "-- Logs begin at …", "-- Reboot --"),
        any warning messages regarding
        inaccessible system journals when run as a normal
        user.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-m</option></term>
        <term><option>--merge</option></term>

        <listitem><para>Show entries interleaved from all available
        journals, including remote ones.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-b <optional><replaceable>ID</replaceable></optional><optional><replaceable>±offset</replaceable></optional></option></term>
        <term><option>--boot=<optional><replaceable>ID</replaceable></optional><optional><replaceable>±offset</replaceable></optional></option></term>

        <listitem><para>Show messages from a specific boot. This will
        add a match for <literal>_BOOT_ID=</literal>.</para>

        <para>The argument may be empty, in which case logs for the
        current boot will be shown.</para>

        <para>If the boot ID is omitted, a positive
        <replaceable>offset</replaceable> will look up the boots
        starting from the beginning of the journal, and an
        equal-or-less-than zero <replaceable>offset</replaceable> will
        look up boots starting from the end of the journal. Thus,
        <constant>1</constant> means the first boot found in the
        journal in chronological order, <constant>2</constant> the
        second and so on; while <constant>-0</constant> is the last
        boot, <constant>-1</constant> the boot before last, and so
        on. An empty <replaceable>offset</replaceable> is equivalent
        to specifying <constant>-0</constant>, except when the current
        boot is not the last boot (e.g. because
        <option>--directory</option> was specified to look at logs
        from a different machine).</para>

        <para>If the 32-character <replaceable>ID</replaceable> is
        specified, it may optionally be followed by
        <replaceable>offset</replaceable> which identifies the boot
        relative to the one given by boot
        <replaceable>ID</replaceable>. Negative values mean earlier
        boots and positive values mean later boots. If
        <replaceable>offset</replaceable> is not specified, a value of
        zero is assumed, and the logs for the boot given by
        <replaceable>ID</replaceable> are shown.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--list-boots</option></term>

        <listitem><para>Show a tabular list of boot numbers (relative to
        the current boot), their IDs, and the timestamps of the first
        and last message pertaining to the boot.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-k</option></term>
        <term><option>--dmesg</option></term>

        <listitem><para>Show only kernel messages. This implies
        <option>-b</option> and adds the match
        <literal>_TRANSPORT=kernel</literal>.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-t</option></term>
        <term><option>--identifier=<replaceable>SYSLOG_IDENTIFIER</replaceable></option></term>

        <listitem><para>Show messages for the specified syslog
        identifier
        <replaceable>SYSLOG_IDENTIFIER</replaceable>.</para>

        <para>This parameter can be specified multiple
        times.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-u</option></term>
        <term><option>--unit=<replaceable>UNIT</replaceable>|<replaceable>PATTERN</replaceable></option></term>

        <listitem><para>Show messages for the specified systemd unit
        <replaceable>UNIT</replaceable> (such as a service unit), or
        for any of the units matched by
        <replaceable>PATTERN</replaceable>.  If a pattern is
        specified, a list of unit names found in the journal is
        compared with the specified pattern and all that match are
        used. For each unit name, a match is added for messages from
        the unit
        (<literal>_SYSTEMD_UNIT=<replaceable>UNIT</replaceable></literal>),
        along with additional matches for messages from systemd and
        messages about coredumps for the specified unit.</para>

        <para>This parameter can be specified multiple times.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--user-unit=</option></term>

        <listitem><para>Show messages for the specified user session
        unit. This will add a match for messages from the unit
        (<literal>_SYSTEMD_USER_UNIT=</literal> and
        <literal>_UID=</literal>) and additional matches for messages
        from session systemd and messages about coredumps for the
        specified unit.</para>

        <para>This parameter can be specified multiple times.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-p</option></term>
        <term><option>--priority=</option></term>

        <listitem><para>Filter output by message priorities or
        priority ranges. Takes either a single numeric or textual log
        level (i.e. between 0/<literal>emerg</literal> and
        7/<literal>debug</literal>), or a range of numeric/text log
        levels in the form FROM..TO. The log levels are the usual
        syslog log levels as documented in
        <citerefentry project='man-pages'><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
        i.e. <literal>emerg</literal> (0),
        <literal>alert</literal> (1), <literal>crit</literal> (2),
        <literal>err</literal> (3), <literal>warning</literal> (4),
        <literal>notice</literal> (5), <literal>info</literal> (6),
        <literal>debug</literal> (7). If a single log level is
        specified, all messages with this log level or a lower (hence
        more important) log level are shown. If a range is specified,
        all messages within the range are shown, including both the
        start and the end value of the range. This will add
        <literal>PRIORITY=</literal> matches for the specified
        priorities.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-g</option></term>
        <term><option>--grep=</option></term>

        <listitem><para>Filter output to entries where the <varname>MESSAGE=</varname>
        field matches the specified regular expression. PERL-compatible regular expressions
        are used, see
        <citerefentry><refentrytitle>pcre2pattern</refentrytitle><manvolnum>3</manvolnum></citerefentry>
        for a detailed description of the syntax.</para>

        <para>If the pattern is all lowercase, matching is case insensitive.
        Otherwise, matching is case sensitive. This can be overridden with the
        <option>--case-sensitive</option> option, see below.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--case-sensitive<optional>=BOOLEAN</optional></option></term>

        <listitem><para>Make pattern matching case sensitive or case insenstive.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-c</option></term>
        <term><option>--cursor=</option></term>

        <listitem><para>Start showing entries from the location in the
        journal specified by the passed cursor.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--after-cursor=</option></term>

        <listitem><para>Start showing entries from the location in the
        journal <emphasis>after</emphasis> the location specified by
        the passed cursor.  The cursor is shown when the
        <option>--show-cursor</option> option is used.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--show-cursor</option></term>

        <listitem><para>The cursor is shown after the last entry after
        two dashes:</para>
        <programlisting>-- cursor: s=0639…</programlisting>
        <para>The format of the cursor is private
        and subject to change.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-S</option></term>
        <term><option>--since=</option></term>
        <term><option>-U</option></term>
        <term><option>--until=</option></term>

        <listitem><para>Start showing entries on or newer than the specified date, or on or older than the specified
        date, respectively. Date specifications should be of the format <literal>2012-10-30 18:17:16</literal>.  If the
        time part is omitted, <literal>00:00:00</literal> is assumed.  If only the seconds component is omitted,
        <literal>:00</literal> is assumed. If the date component is omitted, the current day is assumed. Alternatively
        the strings <literal>yesterday</literal>, <literal>today</literal>, <literal>tomorrow</literal> are understood,
        which refer to 00:00:00 of the day before the current day, the current day, or the day after the current day,
        respectively. <literal>now</literal> refers to the current time. Finally, relative times may be specified,
        prefixed with <literal>-</literal> or <literal>+</literal>, referring to times before or after the current
        time, respectively. For complete time and date specification, see
        <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Note that
        <option>--output=short-full</option> prints timestamps that follow precisely this format.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-F</option></term>
        <term><option>--field=</option></term>

        <listitem><para>Print all possible data values the specified
        field can take in all entries of the journal.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-N</option></term>
        <term><option>--fields</option></term>

        <listitem><para>Print all field names currently used in all entries of the journal.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--system</option></term>
        <term><option>--user</option></term>

        <listitem><para>Show messages from system services and the
        kernel (with <option>--system</option>). Show messages from
        service of current user (with <option>--user</option>).  If
        neither is specified, show all messages that the user can see.
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-M</option></term>
        <term><option>--machine=</option></term>

        <listitem><para>Show messages from a running, local
        container. Specify a container name to connect to.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>-D <replaceable>DIR</replaceable></option></term>
        <term><option>--directory=<replaceable>DIR</replaceable></option></term>

        <listitem><para>Takes a directory path as argument. If
        specified, journalctl will operate on the specified journal
        directory <replaceable>DIR</replaceable> instead of the
        default runtime and system journal paths.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--file=<replaceable>GLOB</replaceable></option></term>

        <listitem><para>Takes a file glob as an argument. If
        specified, journalctl will operate on the specified journal
        files matching <replaceable>GLOB</replaceable> instead of the
        default runtime and system journal paths. May be specified
        multiple times, in which case files will be suitably
        interleaved.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--root=<replaceable>ROOT</replaceable></option></term>

        <listitem><para>Takes a directory path as an argument. If
        specified, journalctl will operate on journal directories and catalog file hierarchy
        underneath the specified directory instead of the root
        directory (e.g. <option>--update-catalog</option> will create
        <filename><replaceable>ROOT</replaceable>/var/lib/systemd/catalog/database</filename>,
        and journal files under <filename><replaceable>ROOT</replaceable>/run/journal</filename>
        or <filename><replaceable>ROOT</replaceable>/var/log/journal</filename> will be displayed).
        </para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--header</option></term>

        <listitem><para>Instead of showing journal contents, show
        internal header information of the journal fields
        accessed.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--disk-usage</option></term>

        <listitem><para>Shows the current disk usage of all journal
        files. This shows the sum of the disk usage of all archived
        and active journal files.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--vacuum-size=</option></term>
        <term><option>--vacuum-time=</option></term>
        <term><option>--vacuum-files=</option></term>

        <listitem><para>Removes the oldest archived journal files until the disk space they use falls below the
        specified size (specified with the usual <literal>K</literal>, <literal>M</literal>, <literal>G</literal> and
        <literal>T</literal> suffixes), or all archived journal files contain no data older than the specified timespan
        (specified with the usual <literal>s</literal>, <literal>m</literal>, <literal>h</literal>,
        <literal>days</literal>, <literal>months</literal>, <literal>weeks</literal> and <literal>years</literal>
        suffixes), or no more than the specified number of separate journal files remain. Note that running
        <option>--vacuum-size=</option> has only an indirect effect on the output shown by
        <option>--disk-usage</option>, as the latter includes active journal files, while the vacuuming operation only
        operates on archived journal files. Similarly, <option>--vacuum-files=</option> might not actually reduce the
        number of journal files to below the specified number, as it will not remove active journal
        files.</para>

        <para><option>--vacuum-size=</option>, <option>--vacuum-time=</option> and <option>--vacuum-files=</option>
        may be combined in a single invocation to enforce any combination of a size, a time and a number of files limit
        on the archived journal files. Specifying any of these three parameters as zero is equivalent to not enforcing
        the specific limit, and is thus redundant.</para>

        <para>These three switches may also be combined with <option>--rotate</option> into one command. If so, all
        active files are rotated first, and the requested vacuuming operation is executed right after. The rotation has
        the effect that all currently active files are archived (and potentially new, empty journal files opened as
        replacement), and hence the vacuuming operation has the greatest effect as it can take all log data written so
        far into account.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--list-catalog
        <optional><replaceable>128-bit-ID…</replaceable></optional>
        </option></term>

        <listitem><para>List the contents of the message catalog as a
        table of message IDs, plus their short description strings.
        </para>

        <para>If any <replaceable>128-bit-ID</replaceable>s are
        specified, only those entries are shown.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--dump-catalog
        <optional><replaceable>128-bit-ID…</replaceable></optional>
        </option></term>

        <listitem><para>Show the contents of the message catalog, with
        entries separated by a line consisting of two dashes and the
        ID (the format is the same as <filename>.catalog</filename>
        files).</para>

        <para>If any <replaceable>128-bit-ID</replaceable>s are
        specified, only those entries are shown.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--update-catalog</option></term>

        <listitem><para>Update the message catalog index. This command
        needs to be executed each time new catalog files are
        installed, removed, or updated to rebuild the binary catalog
        index.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--setup-keys</option></term>

        <listitem><para>Instead of showing journal contents, generate
        a new key pair for Forward Secure Sealing (FSS). This will
        generate a sealing key and a verification key. The sealing key
        is stored in the journal data directory and shall remain on
        the host. The verification key should be stored
        externally. Refer to the <option>Seal=</option> option in
        <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
        for information on Forward Secure Sealing and for a link to a
        refereed scholarly paper detailing the cryptographic theory it
        is based on.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--force</option></term>

        <listitem><para>When <option>--setup-keys</option> is passed
        and Forward Secure Sealing (FSS) has already been configured,
        recreate FSS keys.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--interval=</option></term>

        <listitem><para>Specifies the change interval for the sealing
        key when generating an FSS key pair with
        <option>--setup-keys</option>. Shorter intervals increase CPU
        consumption but shorten the time range of undetectable journal
        alterations. Defaults to 15min.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--verify</option></term>

        <listitem><para>Check the journal file for internal
        consistency. If the file has been generated with FSS enabled and
        the FSS verification key has been specified with
        <option>--verify-key=</option>, authenticity of the journal file
        is verified.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--verify-key=</option></term>

        <listitem><para>Specifies the FSS verification key to use for
        the <option>--verify</option> operation.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--sync</option></term>

        <listitem><para>Asks the journal daemon to write all yet
        unwritten journal data to the backing file system and
        synchronize all journals. This call does not return until the
        synchronization operation is complete. This command guarantees
        that any log messages written before its invocation are safely
        stored on disk at the time it returns.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--flush</option></term>

        <listitem><para>Asks the journal daemon to flush any log data
        stored in <filename>/run/log/journal</filename> into
        <filename>/var/log/journal</filename>, if persistent storage
        is enabled. This call does not return until the operation is
        complete. Note that this call is idempotent: the data is only
        flushed from <filename>/run/log/journal</filename> into
        <filename>/var/log/journal</filename> once during system
        runtime, and this command exits cleanly without executing any
        operation if this has already happened. This command
        effectively guarantees that all data is flushed to
        <filename>/var/log/journal</filename> at the time it
        returns.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><option>--rotate</option></term>

        <listitem><para>Asks the journal daemon to rotate journal files. This call does not return until the rotation
        operation is complete. Journal file rotation has the effect that all currently active journal files are marked
        as archived and renamed, so that they are never written to in future. New (empty) journal files are then
        created in their place. This operation may be combined with <option>--vacuum-size=</option>,
        <option>--vacuum-time=</option> and <option>--vacuum-file=</option> into a single command, see
        above.</para></listitem>
      </varlistentry>

      <xi:include href="standard-options.xml" xpointer="help" />
      <xi:include href="standard-options.xml" xpointer="version" />
      <xi:include href="standard-options.xml" xpointer="no-pager" />
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Exit status</title>

    <para>On success, 0 is returned; otherwise, a non-zero failure
    code is returned.</para>
  </refsect1>

  <xi:include href="less-variables.xml" />

  <refsect1>
    <title>Examples</title>

    <para>Without arguments, all collected logs are shown
    unfiltered:</para>

    <programlisting>journalctl</programlisting>

    <para>With one match specified, all entries with a field matching
    the expression are shown:</para>

    <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service
journalctl _SYSTEMD_CGROUP=/user.slice/user-42.slice/session-c1.scope</programlisting>

    <para>If two different fields are matched, only entries matching
    both expressions at the same time are shown:</para>

    <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097</programlisting>

    <para>If two matches refer to the same field, all entries matching
    either expression are shown:</para>

    <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service</programlisting>

    <para>If the separator <literal>+</literal> is used, two
    expressions may be combined in a logical OR. The following will
    show all messages from the Avahi service process with the PID
    28097 plus all messages from the D-Bus service (from any of its
    processes):</para>

    <programlisting>journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097 + _SYSTEMD_UNIT=dbus.service</programlisting>

    <para>To show all fields emitted <emphasis>by</emphasis> a unit and <emphasis>about</emphasis>
    the unit, option <option>-u</option>/<option>--unit=</option> should be used.
    <command>journalctl -u <replaceable>name</replaceable></command>
    expands to a complex filter similar to
    <programlisting>_SYSTEMD_UNIT=<replaceable>name</replaceable>.service
  + UNIT=<replaceable>name</replaceable>.service _PID=1
  + OBJECT_SYSTEMD_UNIT=<replaceable>name</replaceable>.service _UID=0
  + COREDUMP_UNIT=<replaceable>name</replaceable>.service _UID=0 MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1
    </programlisting>
    (see <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>5</manvolnum></citerefentry>
    for an explanation of those patterns).
    </para>

    <para>Show all logs generated by the D-Bus executable:</para>

    <programlisting>journalctl /usr/bin/dbus-daemon</programlisting>

    <para>Show all kernel logs from previous boot:</para>

    <programlisting>journalctl -k -b -1</programlisting>

    <para>Show a live log display from a system service
    <filename>apache.service</filename>:</para>

    <programlisting>journalctl -f -u apache</programlisting>

  </refsect1>

  <refsect1>
    <title>See Also</title>
    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>coredumpctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-journal-remote.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>systemd-journal-upload.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
    </para>
  </refsect1>
</refentry>