JOURNALCTL(1)
Query the systemd journal. Static snapshot from Ubuntu 24.04.5 LTS.
JOURNALCTL(1) journalctl JOURNALCTL(1)
NAME
journalctl - Print log entries from the systemd journal
SYNOPSIS
journalctl [OPTIONS...] [MATCHES...]
DESCRIPTION
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.
SOURCE OPTIONS
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.
--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.
FILTERING OPTIONS
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.
-t, --identifier=SYSLOG_IDENTIFIER
Show messages for the specified syslog identifier SYSLOG_IDENTIFIER.
This parameter can be specified multiple times.
Added in version 217.
-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 implies -b and adds the match
"_TRANSPORT=kernel".
Added in version 205.
OUTPUT OPTIONS
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, please refer to the Message
Catalog Developer Documentation[7].
Note: when attaching journalctl output to bug reports, please do not use
-x.
Added in version 196.
--no-hostname
Don't 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.
--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.
PAGER CONTROL OPTIONS
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 -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.
Added in version 198.
FORWARD SECURE SEALING (FSS) OPTIONS
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.
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.
COMMANDS
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.
Added in version 209.
--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.
EXIT STATUS
On success, 0 is returned; otherwise, a non-zero failure code is returned.
ENVIRONMENT
$SYSTEMD_LOG_LEVEL
The maximum log level of emitted messages (messages with a higher log
level, i.e. less important ones, will be suppressed). 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.
$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 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.
Note: if $SYSTEMD_PAGERSECURE is not set, $SYSTEMD_PAGER (as well as
$PAGER) will be silently 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.
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).
$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 completely disable the pager using --no-pager instead.
$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.
EXAMPLES
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
SEE ALSO
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)
NOTES
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. Message Catalog Developer Documentation
https://www.freedesktop.org/wiki/Software/systemd/catalog
systemd 255 JOURNALCTL(1)
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