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systemd/man/journalctl.xml
Jörg Sommer d9e15cbd18 journalctl: New option --cursor-file 
The option cursor-file takes a filename as argument. If the file exists and
contains a valid cursor, this is used to start the output after this position.
At the end, the last cursor gets written to the file.

This allows for an easy implementation of a timer that regularly looks in the
journal for some messages.

    journalctl --cursor-file err-cursor -b -p err
    journalctl --cursor-file audit-cursor -t audit --grep DENIED

Or you might want to walk the journal in steps of 10 messages:

    journalctl --cursor-file ./curs -n10 --since=today -t systemd
2019-02-27 18:43:31 +01:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
-->
<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; lines of level DEBUG
are colored lighter grey; 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>--cursor-file=<replaceable>FILE</replaceable></option></term>
<listitem><para>If <replaceable>FILE</replaceable> exists and contains a
cursor, start showing entries <emphasis>after</emphasis> this location.
Otherwise the show entries according the other given options. At the end,
write the cursor of the last entry to <replaceable>FILE</replaceable>. Use
this option to continually read the journal by sequentially calling
<command>journalctl</command>.</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>
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