'\" t
.TH "SYSTEMD\-TIMESYNCD\&.SERVICE" "8" "" "systemd 257.5" "systemd-timesyncd.service"
.\" -----------------------------------------------------------------
.\" * Define some portability stuff
.\" -----------------------------------------------------------------
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.\" http://bugs.debian.org/507673
.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.SH "NAME"
systemd-timesyncd.service, systemd-timesyncd \- Network Time Synchronization
.SH "SYNOPSIS"
.PP
systemd\-timesyncd\&.service
.PP
/usr/lib/systemd/systemd\-timesyncd
.SH "DESCRIPTION"
.PP
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\&.
.PP
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\&.
.PP
The NTP servers contacted are determined from the global settings in
\fBtimesyncd.conf\fR(5), the per\-link static settings in
\&.network
files, and the per\-link dynamic settings received over DHCP\&. See
\fBsystemd.network\fR(5)
for further details\&.
.PP
\fBtimedatectl\fR(1)\*(Aqs
\fBset\-ntp\fR
command may be used to enable and start, or disable and stop this service\&.
.PP
\fBtimedatectl\fR(1)\*(Aqs
\fBtimesync\-status\fR
or
\fBshow\-timesync\fR
command can be used to show the current status of this service\&.
.PP
systemd\-timesyncd
initialization delays the start of units that are ordered after
time\-set\&.target
(see
\fBsystemd.special\fR(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
\fBsystemd-time-wait-sync.service\fR(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\&.
.PP
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
\fBsystemd\fR(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\&.
.SH "FILES"
.PP
/var/lib/systemd/timesync/clock
.RS 4
The modification time ("mtime") of this file is updated on each successful NTP synchronization or after each
\fISaveIntervalSec=\fR
time interval, as specified in
\fBtimesyncd.conf\fR(5)\&.
.sp
If present, the modification time of this file is used for the epoch by
\fBsystemd\fR(1)
and
systemd\-timesyncd\&.service\&.
.sp
Added in version 219\&.
.RE
.PP
/run/systemd/timesync/synchronized
.RS 4
A file that is touched on each successful synchronization to assist
systemd\-time\-wait\-sync
and other applications in detecting synchronization to an accurate reference clock\&.
.sp
Added in version 239\&.
.RE
.SH "SEE ALSO"
.PP
\fBsystemd\fR(1), \fBtimesyncd.conf\fR(5), \fBsystemd.network\fR(5), \fBsystemd-networkd.service\fR(8), \fBsystemd-time-wait-sync.service\fR(8), \fBsystemd.special\fR(7), \fBtimedatectl\fR(1), \fBlocaltime\fR(5), \fBhwclock\fR(8)