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).
-M, --machine=¶Show messages from a running, local container. Specify a container name to connect to.
-m, --merge¶Show entries interleaved from all available journals, including remote ones.
-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.
-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.
--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/databaseROOT/run/journal/ROOT/var/log/journal/
--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. For further information on supported disk images, see
systemd-nspawn(1)'s
switch of the same name.
--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).
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.
-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.
--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.
-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.
-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. A match is also added for
"UNIT_SYSTEMD_SLICE=", such that if the provided
UNITUNIT 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.
--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=", such
that if the provided UNITUNIT is a
systemd.slice(5)
unit, all logs of children of the unit will be shown.
This parameter can be specified multiple times.
-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.
-t, --identifier=SYSLOG_IDENTIFIER¶Show messages for the specified syslog identifier
SYSLOG_IDENTIFIER.
This parameter can be specified multiple times.
-T, --exclude-identifier=SYSLOG_IDENTIFIER¶Exclude messages for the specified syslog identifier
SYSLOG_IDENTIFIER.
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.
--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.
-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.
--case-sensitive[=BOOLEAN]¶Make pattern matching case sensitive or case insensitive.
-k, --dmesg¶Show only kernel messages. This implies -b and adds the match
"_TRANSPORT=kernel".
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.
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 timestamps in the RFC 3339 profile of ISO 8601.
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-delta¶as for short-monotonic but includes the time difference
to the previous entry.
Maybe unreliable time differences are marked by a "*".
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 objects, separated by newline characters (see Journal JSON Format for more information). Field values are generally encoded as JSON strings, with three exceptions:
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.)
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.
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).
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.
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 ("application/json-seq").
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.
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.
--truncate-newline¶Truncate each log message at the first newline character on output, so that only the first line of each message is displayed.
--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.
-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.
--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.
--utc¶Express time in Coordinated Universal Time (UTC).
-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.
Note: when attaching journalctl output to bug reports, please do
not use -x.
--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.
--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. 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.
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.
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.
--verify-key=¶Specifies the FSS verification key to use for the --verify
operation.
--force¶When --setup-keys is passed and Forward Secure Sealing (FSS) has
already been configured, recreate FSS keys.
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.
-F, --field=¶Print all possible data values the specified field can take in all entries of the journal.
--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=[+] option, only the
first (when the number prefixed with "N+") or the last (without prefix)
N entries will be shown. When specified with
-r/--reverse, the list will be shown in the reverse order.
--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=[+]
option, only the first (when the number prefixed with "N+") or the last (without
prefix) N entries will be shown. When specified with
-r/--reverse, the list will be shown in the reverse order.
--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=¶--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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
--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.
-h, --help¶--version¶$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 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.
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¶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.
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