systemd-timesyncd.service(8) — Linux manual page

SYSTEMD-T....SERVICE(8) systemd-timesyncd.serviceSYSTEMD-T....SERVICE(8)

NAME

       systemd-timesyncd.service, systemd-timesyncd - Network Time
       Synchronization

SYNOPSIS

       systemd-timesyncd.service

       /usr/lib/systemd/systemd-timesyncd

DESCRIPTION

       systemd-timesyncd is a system service that may be used to
       synchronize the local system clock with a remote Network Time
       Protocol (NTP) server. It also saves the local time to disk every
       time the clock has been synchronized and uses this to possibly
       advance the system realtime clock on subsequent reboots to ensure
       it (roughly) monotonically advances even if the system lacks a
       battery-buffered RTC chip.

       The systemd-timesyncd service implements SNTP only. This
       minimalistic service will step the system clock for large offsets
       or slowly adjust it for smaller deltas. Complex use cases that
       require full NTP support (and where SNTP is not sufficient) are
       not covered by systemd-timesyncd.

       The NTP servers contacted are determined from the global settings
       in timesyncd.conf(5), the per-link static settings in .network
       files, and the per-link dynamic settings received over DHCP. See
       systemd.network(5) for further details.

       timedatectl(1)'s set-ntp command may be used to enable and start,
       or disable and stop this service.

       timedatectl(1)'s timesync-status or show-timesync command can be
       used to show the current status of this service.

       systemd-timesyncd initialization delays the start of units that
       are ordered after time-set.target (see systemd.special(7) for
       details) until the local time has been updated from
       /var/lib/systemd/timesync/clock (see below) in order to make it
       roughly monotonic. It does not delay other units until
       synchronization with an accurate reference time sources has been
       reached. Use systemd-time-wait-sync.service(8) to achieve that,
       which will delay start of units that are ordered after
       time-sync.target until synchronization to an accurate reference
       clock is reached.

FILES

       /var/lib/systemd/timesync/clock
           The modification time ("mtime") of this file is updated on
           each successful NTP synchronization or after each
           SaveIntervalSec= time interval, as specified in
           timesyncd.conf(5).

           When initializing, the local clock is advanced to the
           modification time of this file (if the file timestamp is in
           the past this adjustment is not made). If the file does not
           exist yet, the clock is instead advanced to the modification
           time of /usr/lib/clock-epoch – if it exists – or to a time
           derived from the source tree at build time. This mechanism is
           used to ensure that the system clock remains somewhat
           reasonably initialized and roughly monotonic across reboots,
           in case no battery-buffered local RTC is available.

           Added in version 219.

       /usr/lib/clock-epoch
           The modification time ("mtime") of this file is used for
           advancing the system clock in case
           /var/lib/systemd/timesync/clock does not exist yet, see
           above.

           Added in version 254.

       /run/systemd/timesync/synchronized
           A file that is touched on each successful synchronization, to
           assist systemd-time-wait-sync and other applications to
           detecting synchronization with accurate reference clocks.

           Added in version 239.

SEE ALSO

       systemd(1), timesyncd.conf(5), systemd.network(5),
       systemd-networkd.service(8), systemd-time-wait-sync.service(8),
       systemd.special(7), timedatectl(1), localtime(5), hwclock(8)

COLOPHON

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have
       a bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2024-06-13.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 257~devel                                SYSTEMD-T....SERVICE(8)

Pages that refer to this page: timedatectl(1), systemd.network(5), timesyncd.conf(5), systemd.directives(7), systemd.index(7), systemd.special(7), systemd-timedated.service(8), systemd-time-wait-sync.service(8)

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