|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
JOURNALCTL(1) journalctl JOURNALCTL(1)
journalctl - Print log entries from the systemd journal
journalctl [OPTIONS...] [MATCHES...]
journalctl is used to print the log entries stored in the journal
by systemd-journald.service(8) and
systemd-journal-remote.service(8).
If called without parameters, it will show the contents of the
journal accessible to the calling user, 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 --header option can be used to identify which files
are being shown.
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
WARNING are colored yellow; lines of level NOTICE are highlighted;
lines of level INFO are displayed normally; lines of level DEBUG
are colored grey.
To write entries to the journal, a few methods may be used. In
general, output from systemd units is automatically connected to
the journal, see systemd-journald.service(8). In addition,
systemd-cat(1) may be used to send messages to the journal
directly.
The following options control where to read journal records from:
--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.
The --user option affects how --unit= arguments are treated.
See --unit=.
Note that --user only works if persistent logging is enabled,
via the Storage= setting in journald.conf(5).
Added in version 205.
-M, --machine=
Show messages from a running, local container. Specify a
container name to connect to.
Added in version 209.
-m, --merge
Show entries interleaved from all available journals,
including remote ones.
Added in version 190.
-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.
Added in version 187.
-i GLOB, --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.
Added in version 205.
--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
ROOT/var/lib/systemd/catalog/database, and journal files under
ROOT/run/journal/ or ROOT/var/log/journal/ will be displayed).
Added in version 201.
--image=IMAGE
Takes a path to a disk image file or block device node. If
specified, journalctl will operate on the file system in the
indicated disk image. This option is similar to --root=, but
operates on file systems stored in disk images or block
devices, thus providing an easy way to extract log data from
disk images. The disk image should either contain just a file
system or a set of file systems within a GPT partition table,
following the Discoverable Partitions Specification[1]. For
further information on supported disk images, see
systemd-nspawn(1)'s switch of the same name.
Added in version 247.
--image-policy=policy
Takes an image policy string as argument, as per
systemd.image-policy(7). The policy is enforced when operating
on the disk image specified via --image=, see above. If not
specified, defaults to the "*" policy, i.e. all recognized
file systems in the image are used.
--namespace=NAMESPACE
Takes a journal namespace identifier string as argument. If
not specified, the data collected by the default namespace is
shown. If specified, shows the log data of the specified
namespace instead. If the namespace is specified as "*" data
from all namespaces is shown, interleaved. If the namespace
identifier is prefixed with "+" data from the specified
namespace and the default namespace is shown, interleaved, but
no other. For details about journal namespaces see
systemd-journald.service(8).
Added in version 245.
The following options control how to filter journal records:
-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.
Added in version 195.
-c, --cursor=
Start showing entries from the location in the journal
specified by the passed cursor.
Added in version 193.
--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.
Added in version 206.
--cursor-file=FILE
If FILE exists and contains a cursor, start showing entries
after this location. Otherwise, show entries according to the
other given options. At the end, write the cursor of the last
entry to FILE. Use this option to continually read the journal
by sequentially calling journalctl.
Added in version 242.
-b [[ID][±offset]|all], --boot[=[ID][±offset]|all]
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.
The special argument all can be used to negate the effect of
an earlier use of -b.
Added in version 186.
-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=UNIT"), along with
additional matches for messages from systemd and messages
about coredumps for the specified unit. A match is also added
for "_SYSTEMD_SLICE=UNIT", such that if the provided UNIT is a
systemd.slice(5) unit, all logs of children of the slice will
be shown.
With --user, all --unit= arguments will be converted to match
user messages as if specified with --user-unit=.
This parameter can be specified multiple times.
Added in version 195.
--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. A
match is also added for "_SYSTEMD_USER_SLICE=UNIT", such that
if the provided UNIT is a systemd.slice(5) unit, all logs of
children of the unit will be shown.
This parameter can be specified multiple times.
Added in version 198.
-I, --invocation=ID[±offset]|offset
Show messages from a specific invocation of unit. This will
add a match for "_SYSTEMD_INVOCATION_ID=",
"OBJECT_SYSTEMD_INVOCATION_ID=", "INVOCATION_ID=",
"USER_INVOCATION_ID=".
A positive offset will look up the invocations of a systemd
unit from the beginning of the journal, and zero or a negative
offset will look up invocations starting from the end of the
journal. Thus, 1 means the first invocation found in the
journal in chronological order, 2 the second and so on; while
0 is the latest invocation, -1 the invocation before the
latest, and so on.
If the 32-character ID is specified, it may optionally be
followed by ±offset which identifies the invocation relative
to the one given by invocation ID. Negative values mean
earlier invocations and positive values mean later
invocations. If ±offset is not specified, a value of zero is
assumed, and the logs for the invocation given by ID will be
shown.
-I is equivalent to --invocation=0, and logs for the latest
invocation will be shown.
When an offset is specified, a unit name must be specified
with -u/--unit= or --user-unit= option.
When specified with -b/--boot=, then invocations are searched
within the specified boot.
Added in version 257.
-t, --identifier=SYSLOG_IDENTIFIER
Show messages for the specified syslog identifier
SYSLOG_IDENTIFIER.
This parameter can be specified multiple times.
Added in version 217.
-T, --exclude-identifier=SYSLOG_IDENTIFIER
Exclude messages for the specified syslog identifier
SYSLOG_IDENTIFIER.
This parameter can be specified multiple times.
Added in version 256.
-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.
Added in version 188.
--facility=
Filter output by syslog facility. Takes a comma-separated list
of numbers or facility names. The names are the usual syslog
facilities as documented in syslog(3). --facility=help may be
used to display a list of known facility names and exit.
Added in version 245.
-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.
When used with --lines= (not prefixed with "+"), --reverse is
implied.
Added in version 237.
--case-sensitive[=BOOLEAN]
Make pattern matching case sensitive or case insensitive.
Added in version 237.
-k, --dmesg
Show only kernel messages. This adds the match
"_TRANSPORT=kernel". This implies --boot=0 unless explicitly
specified otherwise.
Added in version 205.
The following options control how journal records are printed:
-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.
Added in version 206.
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.
Added in version 232.
short-iso
is very similar, but shows timestamps in the RFC 3339[2]
profile of ISO 8601.
Added in version 206.
short-iso-precise
as for short-iso but includes full microsecond precision.
Added in version 234.
short-precise
is very similar, but shows classic syslog timestamps with
full microsecond precision.
Added in version 207.
short-monotonic
is very similar, but shows monotonic timestamps instead of
wallclock timestamps.
Added in version 206.
short-delta
as for short-monotonic but includes the time difference to
the previous entry. Maybe unreliable time differences are
marked by a "*".
Added in version 252.
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.
Added in version 230.
verbose
shows the full-structured entry items with all fields.
Added in version 206.
export
serializes the journal into a binary (but mostly
text-based) stream suitable for backups and network
transfer (see Journal Export Format[3] for more
information). To import the binary stream back into native
journald format use systemd-journal-remote(8).
Added in version 206.
json
formats entries as JSON objects, separated by newline
characters (see Journal JSON Format[4] for more
information). Field values are generally encoded as JSON
strings, with three exceptions:
1. Fields larger than 4096 bytes are encoded as null
values. (This may be turned off by passing --all, but
be aware that this may allocate overly long JSON
objects.)
2. 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.
3. Fields containing non-printable or non-UTF8 bytes are
encoded as arrays containing the raw bytes
individually formatted as unsigned numbers.
Note that this encoding is reversible (with the exception
of the size limit).
Added in version 206.
json-pretty
formats entries as JSON data structures, but formats them
in multiple lines in order to make them more readable by
humans.
Added in version 206.
json-sse
formats entries as JSON data structures, but wraps them in
a format suitable for Server-Sent Events[5].
Added in version 206.
json-seq
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 JavaScript Object Notation (JSON) Text
Sequences[6] ("application/json-seq").
Added in version 240.
cat
generates a very terse output, only showing the actual
message of each journal entry with no metadata, not even a
timestamp. If combined with the --output-fields= option
will output the listed fields for each log record, instead
of the message.
Added in version 206.
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.
Added in version 239.
--truncate-newline
Truncate each log message at the first newline character on
output, so that only the first line of each message is
displayed.
Added in version 254.
--output-fields=
A comma separated list of the fields which should be included
in the output. This has an effect only for the output modes
which would normally show all fields (verbose, export, json,
json-pretty, json-sse and json-seq), as well as on cat. For
the former, the "__CURSOR", "__REALTIME_TIMESTAMP",
"__MONOTONIC_TIMESTAMP", and "_BOOT_ID" fields are always
printed.
Added in version 236.
-n, --lines=
Show the most recent journal events and limit the number of
events shown. The argument is a positive integer or "all" to
disable the limit. Additionally, if the number is prefixed
with "+", the oldest journal events are used instead. The
default value is 10 if no argument is given.
If --follow is used, this option is implied. When not prefixed
with "+" and used with --grep=, --reverse is implied.
-r, --reverse
Reverse output so that the newest entries are displayed first.
Added in version 198.
--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.
Added in version 209.
--utc
Express time in Coordinated Universal Time (UTC).
Added in version 217.
-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,
see Journal Message Catalogs[7].
Note: when attaching journalctl output to bug reports, please
do not use -x.
Added in version 196.
--no-hostname
Do not show the hostname field of log messages originating
from the local host. This switch has an effect only on the
short family of output modes (see above).
Note: this option does not remove occurrences of the hostname
from log entries themselves, so it does not prevent the
hostname from being visible in the logs.
Added in version 230.
--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.
Added in version 196.
-a, --all
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.)
-f, --follow
Show only the most recent journal entries, and continuously
print new entries as they are appended to the journal, until
Ctrl-C is hit (or the tool is otherwise terminated).
journalctl will send an sd_notify(3) "READY=1" message once it
initialized and successfully established its watch on the
journal.
--no-tail
Show all stored output lines, even in follow mode. Undoes the
effect of --lines=.
-q, --quiet
Suppresses all informational messages (i.e. "-- Journal begins
at ...", "-- Reboot --"), any warning messages regarding
inaccessible system journals when run as a normal user.
--synchronize-on-exit=
Takes a boolean argument. If true and operating in --follow
mode, a journal synchronization request (equivalent to
journalctl --sync) is issued when SIGTERM/SIGINT is received,
and log output continues until this request completes. This is
useful for synchronizing journal log output to the runtime of
services or external events, ensuring that any log data
enqueued to the logging subsystem by the time SIGTERM/SIGINT
is issued is guaranteed to be processed and displayed by the
time log output ends. Defaults to false.
Added in version 258.
The following options control page support:
--no-pager
Do not pipe output into a pager.
-e, --pager-end
Immediately jump to the end of the journal inside the implied
pager tool. This implies --lines=1000 and --boot=0 unless
explicitly specified otherwise, to guarantee that the pager
will not buffer logs of unbounded size. Note that this option
is only supported for the less(1) pager.
Added in version 198.
The following options may be used together with the --setup-keys
command described below:
--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.
Note, --output=json-sse and --output=json-seq are silently
migrated to --output=json.
Added in version 189.
--verify-key=
Specifies the FSS verification key to use for the --verify
operation.
Added in version 189.
--force
When --setup-keys is passed and Forward Secure Sealing (FSS)
has already been configured, recreate FSS keys.
Added in version 206.
The following commands are understood. If none is specified the
default is to display journal records:
-N, --fields
Print all field names currently used in all entries of the
journal.
Added in version 229.
-F, --field=
Print all possible data values the specified field can take in
all entries of the journal.
Added in version 195.
--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. When specified with
-n/--lines=[+]N option, only the first (when the number
prefixed with "+") or the last (without prefix) N entries will
be shown. When specified with -r/--reverse, the list will be
shown in the reverse order.
Added in version 209.
--list-invocations
List invocation IDs of a unit. Requires a unit name with
-u/--unit= or --user-unit=. Show a tabular list of invocation
numbers (relative to the current or latest invocation), their
IDs, and the timestamps of the first and last message
pertaining to the invocation. When -b/-boot is specified,
invocations in the boot will be shown. When specified with
-n/--lines=[+]N option, only the first (when the number
prefixed with "+") or the last (without prefix) N entries will
be shown. When specified with -r/--reverse, the list will be
shown in the reverse order.
Added in version 257.
--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.
Added in version 190.
--vacuum-size=, --vacuum-time=, --vacuum-files=
--vacuum-size= removes the oldest archived journal files until
the disk space they use falls below the specified size.
Accepts the usual "K", "M", "G" and "T" suffixes (to the base
of 1024).
--vacuum-time= removes archived journal files older than the
specified timespan. Accepts the usual "s" (default), "m", "h",
"days", "weeks", "months", and "years" suffixes, see
systemd.time(7) for details.
--vacuum-files= leaves only the specified number of separate
journal files.
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.
These three switches may also be combined with --rotate 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.
Added in version 218.
--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.
Added in version 189.
--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.
Added in version 228.
--relinquish-var
Asks the journal daemon for the reverse operation to --flush:
if requested the daemon will write further log data to
/run/log/journal/ and stops writing to /var/log/journal/. A
subsequent call to --flush causes the log output to switch
back to /var/log/journal/, see above.
Added in version 243.
--smart-relinquish-var
Similar to --relinquish-var, but executes no operation if the
root file system and /var/log/journal/ reside on the same
mount point. This operation is used during system shutdown in
order to make the journal daemon stop writing data to
/var/log/journal/ in case that directory is located on a mount
point that needs to be unmounted.
Added in version 243.
--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 (but see
--relinquish-var below), 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.
Added in version 217.
--rotate
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 --vacuum-size=, --vacuum-time= and --vacuum-file= into a
single command, see above.
Added in version 227.
--header
Instead of showing journal contents, show internal header
information of the journal fields accessed.
This option is particularly useful when trying to identify
out-of-order journal entries, as happens for example when the
machine is booted with the wrong system time.
Added in version 187.
--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-IDs are specified, only those entries are
shown.
Added in version 196.
--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-IDs are specified, only those entries are
shown.
Added in version 199.
--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.
Added in version 196.
--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.
Added in version 189.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
On success, 0 is returned; otherwise, a non-zero failure code is
returned.
$SYSTEMD_LOG_LEVEL
The maximum log level of emitted messages (messages with a
higher log level, i.e. less important ones, will be
suppressed). Takes a comma-separated list of values. A value
may be either one of (in order of decreasing importance)
emerg, alert, crit, err, warning, notice, info, debug, or an
integer in the range 0...7. See syslog(3) for more
information. Each value may optionally be prefixed with one of
console, syslog, kmsg or journal followed by a colon to set
the maximum log level for that specific log target (e.g.
SYSTEMD_LOG_LEVEL=debug,console:info specifies to log at debug
level except when logging to the console which should be at
info level). Note that the global maximum log level takes
priority over any per target maximum log levels.
$SYSTEMD_LOG_COLOR
A boolean. If true, messages written to the tty will be
colored according to priority.
This setting is only useful when messages are written directly
to the terminal, because journalctl(1) and other tools that
display logs will color messages based on the log level on
their own.
$SYSTEMD_LOG_TIME
A boolean. If true, console log messages will be prefixed with
a timestamp.
This setting is only useful when messages are written directly
to the terminal or a file, because journalctl(1) and other
tools that display logs will attach timestamps based on the
entry metadata on their own.
$SYSTEMD_LOG_LOCATION
A boolean. If true, messages will be prefixed with a filename
and line number in the source code where the message
originates.
Note that the log location is often attached as metadata to
journal entries anyway. Including it directly in the message
text can nevertheless be convenient when debugging programs.
$SYSTEMD_LOG_TID
A boolean. If true, messages will be prefixed with the current
numerical thread ID (TID).
Note that the this information is attached as metadata to
journal entries anyway. Including it directly in the message
text can nevertheless be convenient when debugging programs.
$SYSTEMD_LOG_TARGET
The destination for log messages. One of console (log to the
attached tty), console-prefixed (log to the attached tty but
with prefixes encoding the log level and "facility", see
syslog(3), kmsg (log to the kernel circular log buffer),
journal (log to the journal), journal-or-kmsg (log to the
journal if available, and to kmsg otherwise), auto (determine
the appropriate log target automatically, the default), null
(disable log output).
$SYSTEMD_LOG_RATELIMIT_KMSG
Whether to ratelimit kmsg or not. Takes a boolean. Defaults to
"true". If disabled, systemd will not ratelimit messages
written to kmsg.
$SYSTEMD_PAGER, $PAGER
Pager to use when --no-pager is not given. $SYSTEMD_PAGER is
used if set; otherwise $PAGER is used. If neither
$SYSTEMD_PAGER nor $PAGER are set, a set of well-known pager
implementations is tried in turn, including less(1) and
more(1), until one is found. If no pager implementation is
discovered, no pager is invoked. Setting those environment
variables to an empty string or the value "cat" is equivalent
to passing --no-pager.
Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER and
$PAGER can only be used to disable the pager (with "cat" or
""), and are otherwise ignored.
$SYSTEMD_LESS
Override the options passed to less (by default "FRSXMK").
Users might want to change two options in particular:
K
This option instructs the pager to exit immediately when
Ctrl+C is pressed. To allow less to handle Ctrl+C itself
to switch back to the pager command prompt, unset this
option.
If the value of $SYSTEMD_LESS does not include "K", and
the pager that is invoked is less, Ctrl+C will be ignored
by the executable, and needs to be handled by the pager.
X
This option instructs the pager to not send termcap
initialization and deinitialization strings to the
terminal. It is set by default to allow command output to
remain visible in the terminal even after the pager exits.
Nevertheless, this prevents some pager functionality from
working, in particular paged output cannot be scrolled
with the mouse.
Note that setting the regular $LESS environment variable has
no effect for less invocations by systemd tools.
See less(1) for more discussion.
$SYSTEMD_LESSCHARSET
Override the charset passed to less (by default "utf-8", if
the invoking terminal is determined to be UTF-8 compatible).
Note that setting the regular $LESSCHARSET environment
variable has no effect for less invocations by systemd tools.
$SYSTEMD_PAGERSECURE
Common pager commands like less(1), in addition to "paging",
i.e. scrolling through the output, support opening of or
writing to other files and running arbitrary shell commands.
When commands are invoked with elevated privileges, for
example under sudo(8) or pkexec(1), the pager becomes a
security boundary. Care must be taken that only programs with
strictly limited functionality are used as pagers, and
unintended interactive features like opening or creation of
new files or starting of subprocesses are not allowed. "Secure
mode" for the pager may be enabled as described below, if the
pager supports that (most pagers are not written in a way that
takes this into consideration). It is recommended to either
explicitly enable "secure mode" or to completely disable the
pager using --no-pager or PAGER=cat when allowing untrusted
users to execute commands with elevated privileges.
This option takes a boolean argument. When set to true, the
"secure mode" of the pager is enabled. In "secure mode",
LESSSECURE=1 will be set when invoking the pager, which
instructs the pager to disable commands that open or create
new files or start new subprocesses. Currently only less(1) is
known to understand this variable and implement "secure mode".
When set to false, no limitation is placed on the pager.
Setting SYSTEMD_PAGERSECURE=0 or not removing it from the
inherited environment may allow the user to invoke arbitrary
commands.
When $SYSTEMD_PAGERSECURE is not set, systemd tools attempt to
automatically figure out if "secure mode" should be enabled
and whether the pager supports it. "Secure mode" is enabled if
the effective UID is not the same as the owner of the login
session, see geteuid(2) and sd_pid_get_owner_uid(3), or when
running under sudo(8) or similar tools ($SUDO_UID is set [8]).
In those cases, SYSTEMD_PAGERSECURE=1 will be set and pagers
which are not known to implement "secure mode" will not be
used at all. Note that this autodetection only covers the most
common mechanisms to elevate privileges and is intended as
convenience. It is recommended to explicitly set
$SYSTEMD_PAGERSECURE or disable the pager.
Note that if the $SYSTEMD_PAGER or $PAGER variables are to be
honoured, other than to disable the pager,
$SYSTEMD_PAGERSECURE must be set too.
$SYSTEMD_COLORS
Takes a boolean argument. When true, systemd and related
utilities will use colors in their output, otherwise the
output will be monochrome. Additionally, the variable can take
one of the following special values: "16", "256" to restrict
the use of colors to the base 16 or 256 ANSI colors,
respectively. This can be specified to override the automatic
decision based on $TERM and what the console is connected to.
$SYSTEMD_URLIFY
The value must be a boolean. Controls whether clickable links
should be generated in the output for terminal emulators
supporting this. This can be specified to override the
decision that systemd makes based on $TERM and other
conditions.
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(7) 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
systemd(1), systemd-cat(1), systemd-journald.service(8),
systemctl(1), coredumpctl(1), systemd.journal-fields(7),
journald.conf(5), systemd.time(7),
systemd-journal-remote.service(8),
systemd-journal-upload.service(8)
1. Discoverable Partitions Specification
https://uapi-group.org/specifications/specs/discoverable_partitions_specification
2. RFC 3339
https://tools.ietf.org/html/rfc3339
3. Journal Export Format
https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-export-format
4. Journal JSON Format
https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-json-format
5. Server-Sent Events
https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events
6. JavaScript Object Notation (JSON) Text Sequences
https://tools.ietf.org/html/rfc7464
7. Journal Message Catalogs
https://systemd.io/CATALOG
8. It is recommended for other tools to set and check $SUDO_UID
as appropriate, treating it is a common interface.
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have a
bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 258~rc2 JOURNALCTL(1)
Pages that refer to this page: coredumpctl(1), flatpak-history(1), homectl(1), importctl(1), journalctl(1), localectl(1), logger(1), loginctl(1), machinectl(1), pmdasystemd(1), portablectl(1), systemctl(1), systemd(1), systemd-analyze(1), systemd-inhibit(1), systemd-nspawn(1), systemd-vmspawn(1), timedatectl(1), updatectl(1), userdbctl(1), sd-id128(3), sd-journal(3), syslog(3), journald.conf(5), org.freedesktop.LogControl1(5), systemd.exec(5), systemd.kill(5), systemd.directives(7), systemd.index(7), systemd.journal-fields(7), systemd.time(7), systemd-coredump(8), systemd-journald.service(8), systemd-journal-gatewayd.service(8), systemd-journal-remote.service(8), systemd-journal-upload.service(8), systemd-machined.service(8), systemd-pstore.service(8), systemd-tmpfiles(8)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|