systemd-timesyncd.service(8)

1SYSTEMD-TIMESYNCD.SERVICE(8)systemd-timesyncd.servicSeYSTEMD-TIMESYNCD.SERVICE(8)
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NAME

6       systemd-timesyncd.service, systemd-timesyncd - Network Time
7       Synchronization
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SYNOPSIS

10       systemd-timesyncd.service
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12       /usr/lib/systemd/systemd-timesyncd
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DESCRIPTION

15       systemd-timesyncd is a system service that may be used to synchronize
16       the local system clock with a remote Network Time Protocol (NTP)
17       server. It also saves the local time to disk every time the clock has
18       been synchronized and uses this to possibly advance the system realtime
19       clock on subsequent reboots to ensure it (roughly) monotonically
20       advances even if the system lacks a battery-buffered RTC chip.
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22       The systemd-timesyncd service implements SNTP only. This minimalistic
23       service will step the system clock for large offsets or slowly adjust
24       it for smaller deltas. Complex use cases that require full NTP support
25       (and where SNTP is not sufficient) are not covered by
26       systemd-timesyncd.
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28       The NTP servers contacted are determined from the global settings in
29       timesyncd.conf(5), the per-link static settings in .network files, and
30       the per-link dynamic settings received over DHCP. See
31       systemd.network(5) for further details.
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33       timedatectl(1)'s set-ntp command may be used to enable and start, or
34       disable and stop this service.
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36       timedatectl(1)'s timesync-status or show-timesync command can be used
37       to show the current status of this service.
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39       systemd-timesyncd initialization delays the start of units that are
40       ordered after time-set.target (see systemd.special(7) for details)
41       until the local time has been updated from
42       /var/lib/systemd/timesync/clock (see below) in order to make it roughly
43       monotonic. It does not delay other units until synchronization with an
44       accurate reference time sources has been reached. Use systemd-time-
45       wait-sync.service(8) to achieve that, which will delay start of units
46       that are ordered after time-sync.target until synchronization to an
47       accurate reference clock is reached.
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FILES

50       /var/lib/systemd/timesync/clock
51           The modification time ("mtime") of this file is updated on each
52           successful NTP synchronization or after each SaveIntervalSec= time
53           interval, as specified in timesyncd.conf(5).
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55           When initializing, the local clock is advanced to the modification
56           time of this file (if the file timestamp is in the past this
57           adjustment is not made). If the file does not exist yet, the clock
58           is instead advanced to the modification time of
59           /usr/lib/clock-epoch – if it exists – or to a time derived from the
60           source tree at build time. This mechanism is used to ensure that
61           the system clock remains somewhat reasonably initialized and
62           roughly monotonic across reboots, in case no battery-buffered local
63           RTC is available.
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65       /usr/lib/clock-epoch
66           The modification time ("mtime") of this file is used for advancing
67           the system clock in case /var/lib/systemd/timesync/clock does not
68           exist yet, see above.
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70       /run/systemd/timesync/synchronized
71           A file that is touched on each successful synchronization, to
72           assist systemd-time-wait-sync and other applications to detecting
73           synchronization with accurate reference clocks.
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SYNOPSIS

DESCRIPTION

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SEE ALSO