path: root/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>

                <authorgroup>
                        <author>
                                <contrib>Developer</contrib>
                                <firstname>Lennart</firstname>
                                <surname>Poettering</surname>
                                <email>lennart@poettering.net</email>
                        </author>
                </authorgroup>
        </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, if the character
                <literal>+</literal> appears as a separate word on the
                command line, all matches before and after are combined
                in a disjunction (i.e. logical OR).</para>

                <para>As shortcuts for a few types of field/value
                matches, file paths may be specified. If a file path
                refers to an executable file, this is equivalent to an
                <literal>_EXE=</literal> match for the canonicalized
                binary path. Similarly, if a path refers to a device
                node, this is equivalent to a
                <literal>_KERNEL_DEVICE=</literal> match for the
                device.</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>All users are granted access to their private
                per-user journals. However, by default, only root and
                users who are members of the <literal>systemd-journal</literal>
                group get access to the system journal and the
                journals of other users.</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 outputing 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.</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 on the
                                command line. 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,
                                a positive integer, is optional, and
                                defaults to 10. </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-iso</option>
                                                </term>
                                                <listitem>
                                                        <para>is very similar,
                                                        but shows ISO 8601
                                                        wallclock timestamps.
                                                        </para>
                                                </listitem>
                                        </varlistentry>

                                        <varlistentry>
                                                <term>
                                                        <option>short-precise</option>
                                                </term>
                                                <listitem>
                                                        <para>is very similar,
                                                        but shows 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>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="http://www.freedesktop.org/wiki/Software/systemd/export">Journal
                                                        Export Format</ulink>
                                                        for more
                                                        information).</para>
                                                </listitem>
                                        </varlistentry>

                                        <varlistentry>
                                                <term>
                                                        <option>json</option>
                                                </term>
                                                <listitem>
                                                        <para>formats entries
                                                        as JSON data structures,
                                                        one per line (see <ulink
                                                        url="http://www.freedesktop.org/wiki/Software/systemd/json">Journal
                                                        JSON Format</ulink> for
                                                        more information).</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>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>
                                </variablelist>
                                </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="http://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 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 a 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 a 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>-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>, 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>-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 this 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>--since=</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.</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>--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 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>).
                                </para></listitem>
                        </varlistentry>

                        <varlistentry>
                                <term><option>--new-id128</option></term>

                                <listitem><para>Instead of showing
                                journal contents, generate a new 128-bit
                                ID suitable for identifying
                                messages. This is intended for usage
                                by developers who need a new
                                identifier for a new message they
                                introduce and want to make
                                recognizable. This will print the new ID in
                                three different formats which can be
                                copied into source code or
                                similar.</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.</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>

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

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

                <para>Show all logs of the kernel device node <filename noindex='true'>/dev/sda</filename>:</para>

                <programlisting>journalctl /dev/sda</programlisting>

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

                <programlisting>journalctl -k -b -1</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>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>journald.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>