# systemd-timesyncd.service

## NAME



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


## SYNOPSIS



           systemd-timesyncd.service
    
           /usr/lib/systemd/systemd-timesyncd
    


## DESCRIPTION



           systemd-timesyncd.service 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 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.service.
    
           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.
    
           Initialization of systemd-timesyncd.service 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.
    
           **systemd** and **systemd-timesyncd** advance the system clock to the
           "epoch" (the lowest date above which the system clock time is
           assumed to be set correctly). See "System clock epoch" section in
           systemd(1) for details.  **systemd** will set the clock when
           initializing, but /var/lib/systemd/timesync/clock might not yet be
           available at that point.  **systemd-timesyncd** will advance the clock
           when it is started and notices that the system clock is before the
           modification time of /var/lib/systemd/timesync/clock.
    


## 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).
    
               If present, the modification time of this file is used for the
               epoch by systemd(1) and systemd-timesyncd.service.
    
               Added in version 219.
    
           /run/systemd/timesync/synchronized
               A file that is touched on each successful synchronization to
               assist systemd-time-wait-sync.service(8) service and other
               applications in detecting synchronization to an accurate
               reference clock.
    
               Added in version 239.
    


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