TIMESYNCD.CONF(5) timesyncd.conf TIMESYNCD.CONF(5)
NAME
timesyncd.conf, timesyncd.conf.d - Network Time Synchronization
configuration files
SYNOPSIS
/etc/systemd/timesyncd.conf
/etc/systemd/timesyncd.conf.d/*.conf
/run/systemd/timesyncd.conf.d/*.conf
/usr/lib/systemd/timesyncd.conf.d/*.conf
DESCRIPTION
These configuration files control NTP network time synchronization. See
systemd.syntax(7) for a general description of the syntax.
CONFIGURATION DIRECTORIES AND PRECEDENCE
The default configuration is set during compilation, so configuration
is only needed when it is necessary to deviate from those defaults.
Initially, the main configuration file in /etc/systemd/ contains
commented out entries showing the defaults as a guide to the
administrator. Local overrides can be created by editing this file or
by creating drop-ins, as described below. Using drop-ins for local
configuration is recommended over modifications to the main
configuration file.
In addition to the "main" configuration file, drop-in configuration
snippets are read from /usr/lib/systemd/*.conf.d/,
/usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/. Those
drop-ins have higher precedence and override the main configuration
file. Files in the *.conf.d/ configuration subdirectories are sorted by
their filename in lexicographic order, regardless of in which of the
subdirectories they reside. When multiple files specify the same
option, for options which accept just a single value, the entry in the
file sorted last takes precedence, and for options which accept a list
of values, entries are collected as they occur in the sorted files.
When packages need to customize the configuration, they can install
drop-ins under /usr/. Files in /etc/ are reserved for the local
administrator, who may use this logic to override the configuration
files installed by vendor packages. Drop-ins have to be used to
override package drop-ins, since the main configuration file has lower
precedence. It is recommended to prefix all filenames in those
subdirectories with a two-digit number and a dash, to simplify the
ordering of the files.
To disable a configuration file supplied by the vendor, the recommended
way is to place a symlink to /dev/null in the configuration directory
in /etc/, with the same filename as the vendor configuration file.
OPTIONS
The following settings are configured in the [Time] section:
NTP=
A space-separated list of NTP server host names or IP addresses.
During runtime this list is combined with any per-interface NTP
servers acquired from systemd-networkd.service(8).
systemd-timesyncd will contact all configured system or
per-interface servers in turn, until one responds. When the empty
string is assigned, the list of NTP servers is reset, and all prior
assignments will have no effect. This setting defaults to an empty
list.
FallbackNTP=
A space-separated list of NTP server host names or IP addresses to
be used as the fallback NTP servers. Any per-interface NTP servers
obtained from systemd-networkd.service(8) take precedence over this
setting, as do any servers set via NTP= above. This setting is
hence only relevant if no other NTP server information is known.
When the empty string is assigned, the list of NTP servers is
reset, and all prior assignments will have no effect. If this
option is not given, a compiled-in list of NTP servers is used.
RootDistanceMaxSec=
Maximum acceptable root distance, i.e. the maximum estimated time
required for a packet to travel to the server we are connected to
from the server with the reference clock. If the current server
does not satisfy this limit, systemd-timesyncd will switch to a
different server.
Takes a time span value. The default unit is seconds, but other
units may be specified, see systemd.time(5). Defaults to 5 seconds.
PollIntervalMinSec=, PollIntervalMaxSec=
The minimum and maximum poll intervals for NTP messages. Polling
starts at the minimum poll interval, and is adjusted within the
specified limits in response to received packets.
Each setting takes a time span value. The default unit is seconds,
but other units may be specified, see systemd.time(5).
PollIntervalMinSec= defaults to 32 seconds and must not be smaller
than 16 seconds. PollIntervalMaxSec= defaults to 34 min 8 s
(2048 seconds) and must be larger than PollIntervalMinSec=.
ConnectionRetrySec=
Specifies the minimum delay before subsequent attempts to contact a
new NTP server are made.
Takes a time span value. The default unit is seconds, but other
units may be specified, see systemd.time(5). Defaults to 30 seconds
and must not be smaller than 1 second.
SaveIntervalSec=
The interval at which the current time is periodically saved to
disk, in the absence of any recent synchronisation from an NTP
server. This is especially useful for offline systems with no local
RTC, as it will guarantee that the system clock remains roughly
monotonic across reboots.
Takes a time interval value. The default unit is seconds, but other
units may be specified, see systemd.time(5). Defaults to 60
seconds.
SEE ALSO
systemd(1), systemd-timesyncd.service(8), systemd-networkd.service(8)
systemd 252 TIMESYNCD.CONF(5)
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