TIMESYNCD.CONF(5) timesyncd.conf TIMESYNCD.CONF(5)
NAME
timesyncd.conf, timesyncd.conf.d - Network Time Synchronization
configuration files
SYNOPSIS
/etc/systemd/timesyncd.conf
/run/systemd/timesyncd.conf
/usr/local/lib/systemd/timesyncd.conf
/usr/lib/systemd/timesyncd.conf
/etc/systemd/timesyncd.conf.d/*.conf
/run/systemd/timesyncd.conf.d/*.conf
/usr/local/lib/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. The
main configuration file is loaded from one of the listed directories in
order of priority, only the first file found is used: /etc/systemd/,
/run/systemd/, /usr/local/lib/systemd/ [1], /usr/lib/systemd/. The
vendor version of the file contains commented out entries showing the
defaults as a guide to the administrator. Local overrides can also be
created by creating drop-ins, as described below. The main configuration
file can also be edited for this purpose (or a copy in /etc/ if it is
shipped under /usr/), however 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. This also defines a concept of drop-in priorities to allow OS
vendors to ship drop-ins within a specific range lower than the range
used by users. This should lower the risk of package drop-ins overriding
accidentally drop-ins defined by users. It is recommended to use the
range 10-40 for drop-ins in /usr/ and the range 60-90 for drop-ins in
/etc/ and /run/, to make sure that local and transient drop-ins take
priority over drop-ins shipped by the OS vendor.
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.
Added in version 216.
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.
Added in version 216.
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(7). Defaults to 5 seconds.
Added in version 236.
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(7).
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=.
Added in version 236.
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(7). Defaults to 30 seconds
and must not be smaller than 1 second.
Added in version 248.
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(7). Defaults to 60 seconds.
Added in version 250.
SEE ALSO
systemd(1), systemd-timesyncd.service(8), systemd-networkd.service(8)
NOTES
1. 💣💥🧨💥💥💣 Please note that those configuration files must be available
at all times. If /usr/local/ is a separate partition, it may not be
available during early boot, and must not be used for configuration.
systemd 257.13 TIMESYNCD.CONF(5)
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