journalctl — Query the systemd journal
journalctl
[OPTIONS...] [MATCHES...]
journalctl may be used to query the contents of the systemd(1) journal as written by systemd-journald.service(8).
If called without parameters, it will show the full contents of the journal, starting with the oldest entry collected.
If one or more match arguments are passed, the output is
filtered accordingly. A match is in the format
"FIELD=VALUE
",
e.g. "_SYSTEMD_UNIT=httpd.service
", referring
to the components of a structured journal entry. See
systemd.journal-fields(7)
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 "+
" 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).
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 "_EXE=
"
match for the canonicalized binary path is added to the query. If a
file path refers to an executable script, a "_COMM=
"
match for the script name is added to the query. If a file path
refers to a device node, "_KERNEL_DEVICE=
" 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.
Additional constraints may be added using options
--boot
, --unit=
, etc., to
further limit what entries will be shown (logical AND).
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.
The set of journal files which will be used can be
modified using the --user
,
--system
, --directory
, and
--file
options, see below.
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
"systemd-journal
", "adm
", and
"wheel
" can read all journal files. Note
that the two latter groups traditionally have additional
privileges specified by the distribution. Members of the
"wheel
" group can often perform administrative
tasks.
The output is paged through less 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
--no-pager
option and the "Environment" section
below.
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.
The following options are understood:
--no-full
, --full
, -l
¶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.
The old options
-l
/--full
are not useful
anymore, except to undo --no-full
.
-a
, --all
¶Show all fields in full, even if they include unprintable characters or are very long.
-f
, --follow
¶Show only the most recent journal entries, and continuously print new entries as they are appended to the journal.
-e
, --pager-end
¶Immediately jump to the end of the journal
inside the implied pager tool. This implies
-n1000
to guarantee that the pager will not
buffer logs of unbounded size. This may be overridden with
an explicit -n
with some other numeric
value, while -nall
will disable this cap.
Note that this option is only supported for the
less(1)
pager.
-n
, --lines=
¶Show the most recent journal events and
limit the number of events shown. If
--follow
is used, this option is
implied. The argument is a positive integer or
"all
" to disable line limiting. The default
value is 10 if no argument is given.
--no-tail
¶Show all stored output lines, even in follow
mode. Undoes the effect of --lines=
.
-r
, --reverse
¶Reverse output so that the newest entries are displayed first.
-o
, --output=
¶Controls the formatting of the journal entries that are shown. Takes one of the following options:
short
¶is the default and generates an output that is mostly identical to the formatting of classic syslog files, showing one line per journal entry.
short-full
¶is very similar, but shows timestamps in the format the --since=
and
--until=
options accept. Unlike the timestamp information shown in
short
output mode this mode includes weekday, year and timezone information in the
output, and is locale-independent.
short-iso
¶is very similar, but shows ISO 8601 wallclock timestamps.
short-iso-precise
¶as for short-iso
but includes full
microsecond precision.
short-precise
¶is very similar, but shows classic syslog timestamps with full microsecond precision.
short-monotonic
¶is very similar, but shows monotonic timestamps instead of wallclock timestamps.
short-unix
¶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.
verbose
¶shows the full-structured entry items with all fields.
export
¶serializes the journal into a binary (but mostly text-based) stream suitable for backups and network transfer (see Journal Export Format for more information). To import the binary stream back into native journald format use systemd-journal-remote(8).
json
¶formats entries as JSON data structures, one per line (see Journal JSON Format for more information).
json-pretty
¶formats entries as JSON data structures, but formats them in multiple lines in order to make them more readable by humans.
json-sse
¶formats entries as JSON data structures, but wraps them in a format suitable for Server-Sent Events.
cat
¶generates a very terse output, only showing the actual message of each journal entry with no metadata, not even a timestamp.
with-unit
¶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.
--output-fields=
¶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 (verbose
,
export
, json
,
json-pretty
, and json-sse
). The
"__CURSOR
", "__REALTIME_TIMESTAMP
",
"__MONOTONIC_TIMESTAMP
", and
"_BOOT_ID
" fields are always
printed.
--utc
¶Express time in Coordinated Universal Time (UTC).
--no-hostname
¶Don't show the hostname field of log messages originating from the local host. This switch only
has an effect on the short
family of output modes (see above).
-x
, --catalog
¶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 Message Catalog Developer Documentation.
Note: when attaching journalctl
output to bug reports, please do not use
-x
.
-q
, --quiet
¶Suppresses all informational messages (i.e. "-- Logs begin at …", "-- Reboot --"), any warning messages regarding inaccessible system journals when run as a normal user.
-m
, --merge
¶Show entries interleaved from all available journals, including remote ones.
-b [ID
][±offset
]
, --boot=[ID
][±offset
]
¶Show messages from a specific boot. This will
add a match for "_BOOT_ID=
".
The argument may be empty, in which case logs for the current boot will be shown.
If the boot ID is omitted, a positive
offset
will look up the boots
starting from the beginning of the journal, and an
equal-or-less-than zero offset
will
look up boots starting from the end of the journal. Thus,
1
means the first boot found in the
journal in chronological order, 2
the
second and so on; while -0
is the last
boot, -1
the boot before last, and so
on. An empty offset
is equivalent
to specifying -0
, except when the current
boot is not the last boot (e.g. because
--directory
was specified to look at logs
from a different machine).
If the 32-character ID
is
specified, it may optionally be followed by
offset
which identifies the boot
relative to the one given by boot
ID
. Negative values mean earlier
boots and positive values mean later boots. If
offset
is not specified, a value of
zero is assumed, and the logs for the boot given by
ID
are shown.
--list-boots
¶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.
-k
, --dmesg
¶Show only kernel messages. This implies
-b
and adds the match
"_TRANSPORT=kernel
".
-t
, --identifier=SYSLOG_IDENTIFIER
¶Show messages for the specified syslog
identifier
SYSLOG_IDENTIFIER
.
This parameter can be specified multiple times.
-u
, --unit=UNIT
|PATTERN
¶Show messages for the specified systemd unit
UNIT
(such as a service unit), or
for any of the units matched by
PATTERN
. 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
("_SYSTEMD_UNIT=
"),
along with additional matches for messages from systemd and
messages about coredumps for the specified unit.UNIT
This parameter can be specified multiple times.
--user-unit=
¶Show messages for the specified user session
unit. This will add a match for messages from the unit
("_SYSTEMD_USER_UNIT=
" and
"_UID=
") and additional matches for messages
from session systemd and messages about coredumps for the
specified unit.
This parameter can be specified multiple times.
-p
, --priority=
¶Filter output by message priorities or
priority ranges. Takes either a single numeric or textual log
level (i.e. between 0/"emerg
" and
7/"debug
"), 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
syslog(3),
i.e. "emerg
" (0),
"alert
" (1), "crit
" (2),
"err
" (3), "warning
" (4),
"notice
" (5), "info
" (6),
"debug
" (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
"PRIORITY=
" matches for the specified
priorities.
-g
, --grep=
¶Filter output to entries where the MESSAGE=
field matches the specified regular expression. PERL-compatible regular expressions
are used, see
pcre2pattern(3)
for a detailed description of the syntax.
If the pattern is all lowercase, matching is case insensitive.
Otherwise, matching is case sensitive. This can be overridden with the
--case-sensitive
option, see below.
--case-sensitive[=BOOLEAN]
¶Make pattern matching case sensitive or case insenstive.
-c
, --cursor=
¶Start showing entries from the location in the journal specified by the passed cursor.
--after-cursor=
¶Start showing entries from the location in the
journal after the location specified by
the passed cursor. The cursor is shown when the
--show-cursor
option is used.
--show-cursor
¶The cursor is shown after the last entry after two dashes:
-- cursor: s=0639…
The format of the cursor is private and subject to change.
-S
, --since=
, -U
, --until=
¶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 "2012-10-30 18:17:16
". If the
time part is omitted, "00:00:00
" is assumed. If only the seconds component is omitted,
":00
" is assumed. If the date component is omitted, the current day is assumed. Alternatively
the strings "yesterday
", "today
", "tomorrow
" 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. "now
" refers to the current time. Finally, relative times may be specified,
prefixed with "-
" or "+
", referring to times before or after the current
time, respectively. For complete time and date specification, see
systemd.time(7). Note that
--output=short-full
prints timestamps that follow precisely this format.
-F
, --field=
¶Print all possible data values the specified field can take in all entries of the journal.
-N
, --fields
¶Print all field names currently used in all entries of the journal.
--system
, --user
¶Show messages from system services and the
kernel (with --system
). Show messages from
service of current user (with --user
). If
neither is specified, show all messages that the user can see.
-M
, --machine=
¶Show messages from a running, local container. Specify a container name to connect to.
-D DIR
, --directory=DIR
¶Takes a directory path as argument. If
specified, journalctl will operate on the specified journal
directory DIR
instead of the
default runtime and system journal paths.
--file=GLOB
¶Takes a file glob as an argument. If
specified, journalctl will operate on the specified journal
files matching GLOB
instead of the
default runtime and system journal paths. May be specified
multiple times, in which case files will be suitably
interleaved.
--root=ROOT
¶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. --update-catalog
will create
,
and journal files under ROOT
/var/lib/systemd/catalog/database
or ROOT
/run/journal
will be displayed).
ROOT
/var/log/journal
--new-id128
¶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 four different formats which can be copied into source code or similar.
--header
¶Instead of showing journal contents, show internal header information of the journal fields accessed.
--disk-usage
¶Shows the current disk usage of all journal files. This shows the sum of the disk usage of all archived and active journal files.
--vacuum-size=
, --vacuum-time=
, --vacuum-files=
¶Removes the oldest archived journal files until the disk
space they use falls below the specified size (specified with
the usual "K
", "M
",
"G
" and "T
" suffixes), or all
archived journal files contain no data older than the specified
timespan (specified with the usual "s
",
"m
", "h
",
"days
", "months
",
"weeks
" and "years
" suffixes),
or no more than the specified number of separate journal files
remain. Note that running --vacuum-size=
has
only an indirect effect on the output shown by
--disk-usage
, as the latter includes active
journal files, while the vacuuming operation only operates
on archived journal files. Similarly,
--vacuum-files=
might not actually reduce the
number of journal files to below the specified number, as it
will not remove active journal
files. --vacuum-size=
,
--vacuum-time=
and
--vacuum-files=
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.
--list-catalog
[128-bit-ID…
]
¶List the contents of the message catalog as a table of message IDs, plus their short description strings.
If any 128-bit-ID
s are
specified, only those entries are shown.
--dump-catalog
[128-bit-ID…
]
¶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 .catalog
files).
If any 128-bit-ID
s are
specified, only those entries are shown.
--update-catalog
¶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.
--setup-keys
¶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 Seal=
option in
journald.conf(5)
for information on Forward Secure Sealing and for a link to a
refereed scholarly paper detailing the cryptographic theory it
is based on.
--force
¶When --setup-keys
is passed
and Forward Secure Sealing (FSS) has already been configured,
recreate FSS keys.
--interval=
¶Specifies the change interval for the sealing
key when generating an FSS key pair with
--setup-keys
. Shorter intervals increase CPU
consumption but shorten the time range of undetectable journal
alterations. Defaults to 15min.
--verify
¶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
--verify-key=
, authenticity of the journal file
is verified.
--verify-key=
¶Specifies the FSS verification key to use for
the --verify
operation.
--sync
¶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.
--flush
¶Asks the journal daemon to flush any log data
stored in /run/log/journal
into
/var/log/journal
, 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 /run/log/journal
into
/var/log/journal
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
/var/log/journal
at the time it
returns.
--rotate
¶Asks the journal daemon to rotate journal files. This call does not return until the rotation operation is complete.
-h
, --help
¶--version
¶--no-pager
¶Do not pipe output into a pager.
$SYSTEMD_PAGER
¶Pager to use when --no-pager
is not given; overrides
$PAGER
. If neither $SYSTEMD_PAGER
nor $PAGER
are set, a
set of well-known pager implementations are tried in turn, including
less(1) and
more(1), until one is found. If
no pager implementation is discovered no pager is invoked. Setting this environment variable to an empty string
or the value "cat
" is equivalent to passing --no-pager
.
$SYSTEMD_LESS
¶Override the options passed to less (by default
"FRSXMK
").
$SYSTEMD_LESSCHARSET
¶Override the charset passed to less (by default "utf-8
", if
the invoking terminal is determined to be UTF-8 compatible).
$SYSTEMD_PAGERSECURE
¶Takes a boolean argument. When true, the "secure" mode of the pager is enabled; if
false, disabled. If $SYSTEMD_PAGERSECURE
is not set at all, secure mode is enabled
if the effective UID is not the same as the owner of the login session, see geteuid(2) and
sd_pid_get_owner_uid(3).
In secure mode, LESSSECURE=1
will be set when invoking the pager, and the pager shall
disable commands that open or create new files or start new subprocesses. When
$SYSTEMD_PAGERSECURE
is not set at all, pagers which are not known to implement
secure mode will not be used. (Currently only
less(1) implements
secure mode.)
Note: when commands are invoked with elevated privileges, for example under sudo(8) or
pkexec(1), care
must be taken to ensure that unintended interactive features are not enabled. "Secure" mode for the
pager may be enabled automatically as describe above. Setting SYSTEMD_PAGERSECURE=0
or not removing it from the inherited environment allows the user to invoke arbitrary commands. Note
that if the $SYSTEMD_PAGER
or $PAGER
variables are to be
honoured, $SYSTEMD_PAGERSECURE
must be set too. It might be reasonable to completly
disable the pager using --no-pager
instead.
Without arguments, all collected logs are shown unfiltered:
journalctl
With one match specified, all entries with a field matching the expression are shown:
journalctl _SYSTEMD_UNIT=avahi-daemon.service journalctl _SYSTEMD_CGROUP=/user.slice/user-42.slice/session-c1.scope
If two different fields are matched, only entries matching both expressions at the same time are shown:
journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097
If two matches refer to the same field, all entries matching either expression are shown:
journalctl _SYSTEMD_UNIT=avahi-daemon.service _SYSTEMD_UNIT=dbus.service
If the separator "+
" 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):
journalctl _SYSTEMD_UNIT=avahi-daemon.service _PID=28097 + _SYSTEMD_UNIT=dbus.service
To show all fields emitted by a unit and about
the unit, option -u
/--unit=
should be used.
journalctl -u name
expands to a complex filter similar to
_SYSTEMD_UNIT=name
.service + UNIT=name
.service _PID=1 + OBJECT_SYSTEMD_UNIT=name
.service _UID=0 + COREDUMP_UNIT=name
.service _UID=0 MESSAGE_ID=fc2e22bc6ee647b6b90729ab34a250b1
(see systemd.journal-fields(5) for an explanation of those patterns).
Show all logs generated by the D-Bus executable:
journalctl /usr/bin/dbus-daemon
Show all kernel logs from previous boot:
journalctl -k -b -1
Show a live log display from a system service
apache.service
:
journalctl -f -u apache