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TLDR: journalctl (tldr-pages)

Query the systemd journal.

  • Show the latest `n` lines and follow new messages (like `tail --follow` for traditional syslog)
    journalctl {{-n|--lines}} {{n}} {{-f|--follow}}
  • Show all messages with priority level 3 (errors) from the boot before last shutdown
    journalctl {{-b|--boot}} -1 {{-p|--priority}} 3
  • Show all messages by a specific unit
    journalctl {{-u|--unit}} {{unit}}
  • Show logs for a given unit since the last time it started
    journalctl _SYSTEMD_INVOCATION_ID=$(systemctl show --value --property=InvocationID {{unit}})
  • Filter messages within a time range (either timestamp or placeholders like "yesterday")
    journalctl {{-S|--since}} {{now|today|yesterday|tomorrow|...}} {{-U|--until}} "{{YYYY-MM-DD HH:MM:SS}}"
  • Show all messages by a specific process
    journalctl _PID={{pid}}
  • Show all messages by a specific executable
    journalctl {{path/to/executable}}
  • Delete journal logs which are older than 2 days
    journalctl --vacuum-time 2d
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 --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 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. 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.

       --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.

       --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 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.

       -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. "-- Journal begins 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 children of the slice will be
           shown.

           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 children of the unit will be shown.

           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 insensitive.

       -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).

       --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 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[6]. For further information on supported disk
           images, see systemd-nspawn(1)'s switch of the same name.

       --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.

           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.

       --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_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_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_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-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://systemd.io/JOURNAL_EXPORT_FORMATS#journal-export-format

        2. Journal JSON Format
           https://systemd.io/JOURNAL_EXPORT_FORMATS#journal-json-format

        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

        6. Discoverable Partitions Specification
           https://systemd.io/DISCOVERABLE_PARTITIONS



systemd 249                                                                            JOURNALCTL(1)
journalctl(1)
NAME SYNOPSIS DESCRIPTION OPTIONS
-a, --all -f, --follow -e, --pager-end -n, --lines= --no-tail -r, --reverse -o, --output= --output-fields= --utc --no-hostname -x, --catalog -q, --quiet -m, --merge -b [[ID][±offset]|all], --boot[=[ID][±offset]|all] --list-boots -k, --dmesg -t, --identifier=SYSLOG_IDENTIFIER -u, --unit=UNIT|PATTERN --user-unit= -p, --priority= --facility= -g, --grep= --case-sensitive[=BOOLEAN] -c, --cursor= --after-cursor= --show-cursor -S, --since=, -U, --until= -F, --field= -N, --fields -M, --machine= -D DIR, --directory=DIR --header --disk-usage --update-catalog --setup-keys --force --interval= --verify --verify-key= --sync --flush --relinquish-var --smart-relinquish-var --rotate -h, --help --version --no-pager
EXIT STATUS ENVIRONMENT EXAMPLES SEE ALSO NOTES

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