timedatectl — Control the system time and date
timedatectl  [OPTIONS...] {COMMAND}
timedatectl may be used to query and change the system clock and its settings, and enable or disable time synchronization services.
Use systemd-firstboot(1) to initialize the system time zone for mounted (but not booted) system images.
timedatectl may be used to show the current status of time synchronization services, for example systemd-timesyncd.service(8).
The following commands are understood:
Show current settings of the system clock and RTC, including whether network time synchronization is active. If no command is specified, this is the implied default.
Show the same information as status, but in machine readable form.
        This command is intended to be used whenever computer-parsable output is required.
        Use status if you are looking for formatted human-readable output.
By default, empty properties are suppressed. Use --all to show those too.
        To select specific properties to show, use --property=.
Set the system clock to the specified time. This will also update the RTC time accordingly. The time may be specified in the format "2012-10-30 18:17:16".
Set the system time zone to the specified
        value. Available timezones can be listed with
        list-timezones. If the RTC is configured to
        be in the local time, this will also update the RTC time. This
        call will alter the /etc/localtime
        symlink. See
        localtime(5)
        for more information.
List available time zones, one per line. Entries from the list can be set as the system timezone with set-timezone.
Takes a boolean argument. If
        "0", the system is configured to maintain the
        RTC in universal time. If "1", it will
        maintain the RTC in local time instead. Note that maintaining
        the RTC in the local timezone is not fully supported and will
        create various problems with time zone changes and daylight
        saving adjustments. If at all possible, keep the RTC in UTC
        mode. Note that invoking this will also synchronize the RTC
        from the system clock, unless
        --adjust-system-clock is passed (see above).
        This command will change the 3rd line of
        /etc/adjtime, as documented in
        hwclock(8).
        
Takes a boolean argument. Controls whether network time synchronization is active and enabled (if available). If the argument is true, this enables and starts the first existing network synchronization service. If the argument is false, then this disables and stops the known network synchronization services. The way that the list of services is built is described in systemd-timedated.service(8).
The following commands are specific to systemd-timesyncd.service(8).
Show current status of
          systemd-timesyncd.service(8).
          If --monitor is specified, then this will monitor the status updates.
Show the same information as timesync-status, but in machine readable form.
          This command is intended to be used whenever computer-parsable output is required.
          Use timesync-status if you are looking for formatted human-readable output.
By default, empty properties are suppressed. Use --all to show those too.
          To select specific properties to show, use --property=.
INTERFACE SERVER…¶Set the interface specific NTP servers. This command can be used only when the interface is managed by systemd-networkd.
INTERFACE¶Revert the interface specific NTP servers. This command can be used only when the interface is managed by systemd-networkd.
The following options are understood:
--adjust-system-clock¶If set-local-rtc is invoked and this option is passed, the system clock is synchronized from the RTC again, taking the new setting into account. Otherwise, the RTC is synchronized from the system clock.
--monitor¶If timesync-status is invoked and this option is passed, then timedatectl monitors the status of systemd-timesyncd.service(8) and updates the outputs. Use Ctrl+C to terminate the monitoring.
-a, --all¶When showing properties of systemd-timesyncd.service(8), show all properties regardless of whether they are set or not.
-p, --property=¶When showing properties of
        systemd-timesyncd.service(8),
        limit display to certain properties as specified as argument. If not specified, all set properties are shown.
        The argument should be a property name, such as "ServerName". If specified more than once,
        all properties with the specified names are shown.
--value¶When printing properties with show-timesync, only print the value, and skip the
          property name and "=".
-P¶Equivalent to --value --property=, i.e. shows the value of the
      property without the property name or "=". Note that using -P once
      will also affect all properties listed with -p/--property=.
-H, --host=¶Execute the operation remotely. Specify a hostname, or a
      username and hostname separated by "@", to
      connect to. The hostname may optionally be suffixed by a
      port ssh is listening on, separated by ":", and then a
      container name, separated by "/", which
      connects directly to a specific container on the specified
      host. This will use SSH to talk to the remote machine manager
      instance. Container names may be enumerated with
      machinectl -H
      HOST. Put IPv6 addresses in brackets.
-M, --machine=¶Execute operation on a local container. Specify a container name to connect to, optionally
      prefixed by a user name to connect as and a separating "@" character. If the special
      string ".host" is used in place of the container name, a connection to the local
      system is made (which is useful to connect to a specific user's user bus: "--user
      --machine=lennart@.host"). If the "@" syntax is not used, the connection is
      made as root user. If the "@" syntax is used either the left hand side or the right hand
      side may be omitted (but not both) in which case the local user name and ".host" are
      implied.
--no-ask-password¶Do not query the user for authentication for privileged operations.
-h, --help¶--version¶--no-pager¶Do not pipe output into a pager.
$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.
Show current settings:
$ timedatectl
               Local time: Thu 2017-09-21 16:08:56 CEST
           Universal time: Thu 2017-09-21 14:08:56 UTC
                 RTC time: Thu 2017-09-21 14:08:56
                Time zone: Europe/Warsaw (CEST, +0200)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no
Enable network time synchronization:
$ timedatectl set-ntp true ==== AUTHENTICATING FOR org.freedesktop.timedate1.set-ntp === Authentication is required to control whether network time synchronization shall be enabled. Authenticating as: user Password: ******** ==== AUTHENTICATION COMPLETE ===
$ systemctl status systemd-timesyncd.service
● systemd-timesyncd.service - Network Time Synchronization
   Loaded: loaded (/usr/lib/systemd/system/systemd-timesyncd.service; enabled)
   Active: active (running) since Mo 2015-03-30 14:20:38 CEST; 5s ago
     Docs: man:systemd-timesyncd.service(8)
 Main PID: 595 (systemd-timesyn)
   Status: "Using Time Server 216.239.38.15:123 (time4.google.com)."
   CGroup: /system.slice/systemd-timesyncd.service
           └─595 /usr/lib/systemd/systemd-timesyncd
…
Show current status of systemd-timesyncd.service(8):
$ timedatectl timesync-status
       Server: 216.239.38.15 (time4.google.com)
Poll interval: 1min 4s (min: 32s; max 34min 8s)
         Leap: normal
      Version: 4
      Stratum: 1
    Reference: GPS
    Precision: 1us (-20)
Root distance: 335us (max: 5s)
       Offset: +316us
        Delay: 349us
       Jitter: 0
 Packet count: 1
    Frequency: -8.802ppm