journalctl

JOURNALCTL(1) journalctl JOURNALCTL(1)

NAME
journalctl - Query the systemd journal

SYNOPSIS
journalctl [OPTIONS...] [MATCHES...]

DESCRIPTION
journalctl may be used to query the contents of the systemd(1) journal
as written by systemd-journald.service(8).

If called without parameters, it will show the full contents of the
journal, starting with the oldest entry collected.

If one or more match arguments are passed, the output is filtered
accordingly. A match is in the format "FIELD=VALUE", e.g.
"_SYSTEMD_UNIT=httpd.service", referring to the components of a
structured journal entry. See systemd.journal-fields(7) for a list of
well-known fields. If multiple matches are specified matching different
fields, the log entries are filtered by both, i.e. the resulting output
will show only entries matching all the specified matches of this kind.
If two matches apply to the same field, then they are automatically
matched as alternatives, i.e. the resulting output will show entries
matching any of the specified matches for the same field. Finally, the
character "+" may appear as a separate word between other terms on the
command line. This causes all matches before and after to be combined
in a disjunction (i.e. logical OR).

It is also possible to filter the entries by specifying an absolute
file path as an argument. The file path may be a file or a symbolic
link and the file must exist at the time of the query. If a file path
refers to an executable binary, an "_EXE=" match for the canonicalized
binary path is added to the query. If a file path refers to an
executable script, a "_COMM=" match for the script name is added to the
query. If a file path refers to a device node, "_KERNEL_DEVICE="
matches for the kernel name of the device and for each of its ancestor
devices is added to the query. Symbolic links are dereferenced, kernel
names are synthesized, and parent devices are identified from the
environment at the time of the query. In general, a device node is the
best proxy for an actual device, as log entries do not usually contain
fields that identify an actual device. For the resulting log entries to
be correct for the actual device, the relevant parts of the environment
at the time the entry was logged, in particular the actual device
corresponding to the device node, must have been the same as those at
the time of the query. Because device nodes generally change their
corresponding devices across reboots, specifying a device node path
causes the resulting entries to be restricted to those from the current
boot.

Additional constraints may be added using options --boot, --unit=,
etc., to further limit what entries will be shown (logical AND).

Output is interleaved from all accessible journal files, whether they
are rotated or currently being written, and regardless of whether they
belong to the system itself or are accessible user journals.

The set of journal files which will be used can be modified using the
--user, --system, --directory, and --file options, see below.

All users are granted access to their private per-user journals.
However, by default, only root and users who are members of a few
special groups are granted access to the system journal and the
journals of other users. Members of the groups "systemd-journal",
"adm", and "wheel" can read all journal files. Note that the two latter
groups traditionally have additional privileges specified by the
distribution. Members of the "wheel" group can often perform
administrative tasks.

The output is paged through less by default, and long lines are
"truncated" to screen width. The hidden part can be viewed by using the
left-arrow and right-arrow keys. Paging can be disabled; see the
--no-pager option and the "Environment" section below.

When outputting to a tty, lines are colored according to priority:
lines of level ERROR and higher are colored red; lines of level NOTICE
and higher are highlighted; lines of level DEBUG are colored lighter
grey; other lines are displayed normally.

OPTIONS
The following options are understood:

--no-full, --full, -l
Ellipsize fields when they do not fit in available columns. The
default is to show full fields, allowing them to wrap or be
truncated by the pager, if one is used.

The old options -l/--full are not useful anymore, except to undo
--no-full.

-a, --all
Show all fields in full, even if they include unprintable
characters or are very long. 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.

-e, --pager-end
Immediately jump to the end of the journal inside the implied pager
tool. This implies -n1000 to guarantee that the pager will not
buffer logs of unbounded size. This may be overridden with an
explicit -n with some other numeric value, while -nall will disable
this cap. Note that this option is only supported for the less(1)
pager.

-n, --lines=
Show the most recent journal events and limit the number of events
shown. If --follow is used, this option is implied. The argument is
a positive integer or "all" to disable line limiting. The default
value is 10 if no argument is given.

--no-tail
Show all stored output lines, even in follow mode. Undoes the
effect of --lines=.

-r, --reverse
Reverse output so that the newest entries are displayed first.

-o, --output=
Controls the formatting of the journal entries that are shown.
Takes one of the following options:

short
is the default and generates an output that is mostly identical
to the formatting of classic syslog files, showing one line per
journal entry.

short-full
is very similar, but shows timestamps in the format the
--since= and --until= options accept. Unlike the timestamp
information shown in short output mode this mode includes
weekday, year and timezone information in the output, and is
locale-independent.

short-iso
is very similar, but shows ISO 8601 wallclock timestamps.

short-iso-precise
as for short-iso but includes full microsecond precision.

short-precise
is very similar, but shows classic syslog timestamps with full
microsecond precision.

short-monotonic
is very similar, but shows monotonic timestamps instead of
wallclock timestamps.

short-unix
is very similar, but shows seconds passed since January 1st
1970 UTC instead of wallclock timestamps ("UNIX time"). The
time is shown with microsecond accuracy.

verbose
shows the full-structured entry items with all fields.

export
serializes the journal into a binary (but mostly text-based)
stream suitable for backups and network transfer (see Journal
Export Format[1] 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[2] 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).

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[3].

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[4]
("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.

with-unit
similar to short-full, but prefixes the unit and user unit
names instead of the traditional syslog identifier. Useful when
using templated instances, as it will include the arguments in
the unit names.

--output-fields=
A comma separated list of the fields which should be included in
the output. This only has an effect for the output modes which
would normally show all fields (verbose, export, json, json-pretty,
json-sse and json-seq). The "__CURSOR", "__REALTIME_TIMESTAMP",
"__MONOTONIC_TIMESTAMP", and "_BOOT_ID" fields are always printed.

--utc
Express time in Coordinated Universal Time (UTC).

--no-hostname
Don't show the hostname field of log messages originating from the
local host. This switch only has an effect on the short family of
output modes (see above).

-x, --catalog
Augment log lines with explanation texts from the message catalog.
This will add explanatory help texts to log messages in the output
where this is available. These short help texts will explain the
context of an error or log event, possible solutions, as well as
pointers to support forums, developer documentation, and any other
relevant manuals. Note that help texts are not available for all
messages, but only for selected ones. For more information on the
message catalog, please refer to the Message Catalog Developer
Documentation[5].

Note: when attaching journalctl output to bug reports, please do
not use -x.

-q, --quiet
Suppresses all informational messages (i.e. "-- Logs begin at ...",
"-- Reboot --"), any warning messages regarding inaccessible system
journals when run as a normal user.

-m, --merge
Show entries interleaved from all available journals, including
remote ones.

-b [[ID][+-offset]|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.

--list-boots
Show a tabular list of boot numbers (relative to the current boot),
their IDs, and the timestamps of the first and last message
pertaining to the boot.

-k, --dmesg
Show only kernel messages. This implies -b and adds the match
"_TRANSPORT=kernel".

-t, --identifier=SYSLOG_IDENTIFIER
Show messages for the specified syslog identifier
SYSLOG_IDENTIFIER.

This parameter can be specified multiple times.

-u, --unit=UNIT|PATTERN
Show messages for the specified systemd unit UNIT (such as a
service unit), or for any of the units matched by PATTERN. If a
pattern is specified, a list of unit names found in the journal is
compared with the specified pattern and all that match are used.
For each unit name, a match is added for messages from the unit
("_SYSTEMD_UNIT=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 the children
of the slice will be logged.

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=UNIT", such that if the
provided UNIT is a systemd.slice(5) unit, all logs of the children
of the unit will be logged.

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.

--case-sensitive[=BOOLEAN]
Make pattern matching case sensitive or case insenstive.

-c, --cursor=
Start showing entries from the location in the journal specified by
the passed cursor.

--cursor-file=FILE
If FILE exists and contains a cursor, start showing entries after
this location. Otherwise the show entries according 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.

--after-cursor=
Start showing entries from the location in the journal after the
location specified by the passed cursor. The cursor is shown when
the --show-cursor option is used.

--show-cursor
The cursor is shown after the last entry after two dashes:

-- cursor: s=0639...

The format of the cursor is private and subject to change.

-S, --since=, -U, --until=
Start showing entries on or newer than the specified date, or on or
older than the specified date, respectively. Date specifications
should be of the format "2012-10-30 18:17:16". If the time part is
omitted, "00:00:00" is assumed. If only the seconds component is
omitted, ":00" is assumed. If the date component is omitted, the
current day is assumed. Alternatively the strings "yesterday",
"today", "tomorrow" are understood, which refer to 00:00:00 of the
day before the current day, the current day, or the day after the
current day, respectively. "now" refers to the current time.
Finally, relative times may be specified, prefixed with "-" or "+",
referring to times before or after the current time, respectively.
For complete time and date specification, see systemd.time(7). Note
that --output=short-full prints timestamps that follow precisely
this format.

-F, --field=
Print all possible data values the specified field can take in all
entries of the journal.

-N, --fields
Print all field names currently used in all entries of the journal.

--system, --user
Show messages from system services and the kernel (with --system).
Show messages from service of current user (with --user). If
neither is specified, show all messages that the user can see.

-M, --machine=
Show messages from a running, local container. Specify a container
name to connect to.

-D DIR, --directory=DIR
Takes a directory path as argument. If specified, journalctl will
operate on the specified journal directory DIR instead of the
default runtime and system journal paths.

--file=GLOB
Takes a file glob as an argument. If specified, journalctl will
operate on the specified journal files matching GLOB instead of the
default runtime and system journal paths. May be specified multiple
times, in which case files will be suitably interleaved.

--root=ROOT
Takes a directory path as an argument. If specified, journalctl
will operate on journal directories and catalog file hierarchy
underneath the specified directory instead of the root directory
(e.g. --update-catalog will create
ROOT/var/lib/systemd/catalog/database, and journal files under
ROOT/run/journal or ROOT/var/log/journal will be displayed).

--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).

--header
Instead of showing journal contents, show internal header
information of the journal fields accessed.

--disk-usage
Shows the current disk usage of all journal files. This shows the
sum of the disk usage of all archived and active journal files.

--vacuum-size=, --vacuum-time=, --vacuum-files=
Removes the oldest archived journal files until the disk space they
use falls below the specified size (specified with the usual "K",
"M", "G" and "T" suffixes), or all archived journal files contain
no data older than the specified timespan (specified with the usual
"s", "m", "h", "days", "months", "weeks" and "years" suffixes), or
no more than the specified number of separate journal files remain.
Note that running --vacuum-size= has only an indirect effect on the
output shown by --disk-usage, as the latter includes active journal
files, while the vacuuming operation only operates on archived
journal files. Similarly, --vacuum-files= might not actually reduce
the number of journal files to below the specified number, as it
will not remove active journal files.

--vacuum-size=, --vacuum-time= and --vacuum-files= may be combined
in a single invocation to enforce any combination of a size, a time
and a number of files limit on the archived journal files.
Specifying any of these three parameters as zero is equivalent to
not enforcing the specific limit, and is thus redundant.

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.

--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.

--force
When --setup-keys is passed and Forward Secure Sealing (FSS) has
already been configured, recreate FSS keys.

--interval=
Specifies the change interval for the sealing key when generating
an FSS key pair with --setup-keys. Shorter intervals increase CPU
consumption but shorten the time range of undetectable journal
alterations. Defaults to 15min.

--verify
Check the journal file for internal consistency. If the file has
been generated with FSS enabled and the FSS verification key has
been specified with --verify-key=, authenticity of the journal file
is verified.

--verify-key=
Specifies the FSS verification key to use for the --verify
operation.

--sync
Asks the journal daemon to write all yet unwritten journal data to
the backing file system and synchronize all journals. This call
does not return until the synchronization operation is complete.
This command guarantees that any log messages written before its
invocation are safely stored on disk at the time it returns.

--flush
Asks the journal daemon to flush any log data stored in
/run/log/journal/ into /var/log/journal/, if persistent storage is
enabled. This call does not return until the operation is complete.
Note that this call is idempotent: the data is only flushed from
/run/log/journal/ into /var/log/journal once during system runtime
(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.

--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/lib/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.

--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.

-h, --help
Print a short help text and exit.

--version
Print a short version string and exit.

--no-pager
Do not pipe output into a pager.

EXIT STATUS
On success, 0 is returned; otherwise, a non-zero failure code is
returned.

ENVIRONMENT
$SYSTEMD_PAGER
Pager to use when --no-pager is not given; overrides $PAGER. If
neither $SYSTEMD_PAGER nor $PAGER are set, a set of well-known
pager implementations are tried in turn, including less(1) and
more(1), until one is found. If no pager implementation is
discovered no pager is invoked. Setting this environment variable
to an empty string or the value "cat" is equivalent to passing
--no-pager.

$SYSTEMD_LESS
Override the options passed to less (by default "FRSXMK").

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_COLORS
The value must be a boolean. Controls whether colorized output
should be generated. This can be specified to override the decision
that systemd makes 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-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. Journal Export Format
https://www.freedesktop.org/wiki/Software/systemd/export

2. Journal JSON Format
https://www.freedesktop.org/wiki/Software/systemd/json

3. Server-Sent Events
https://developer.mozilla.org/en-US/docs/Server-sent_events/Using_server-sent_events

4. JavaScript Object Notation (JSON) Text Sequences
https://tools.ietf.org/html/rfc7464

5. Message Catalog Developer Documentation
https://www.freedesktop.org/wiki/Software/systemd/catalog

systemd 245 JOURNALCTL(1)

journalctl

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