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NAME | SYNOPSIS | DESCRIPTION | CONFIGURATION DIRECTORIES AND PRECEDENCE | OPTIONS | SEE ALSO | NOTES | COLOPHON |
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TIMESYNCD.CONF(5) timesyncd.conf TIMESYNCD.CONF(5)
timesyncd.conf, timesyncd.conf.d - Network Time Synchronization
configuration files
/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
These configuration files control NTP network time
synchronization. See systemd.syntax(7) for a general description
of the syntax.
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's 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.
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(5). 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(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=.
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(5). 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(5). Defaults
to 60 seconds.
Added in version 250.
systemd(1), systemd-timesyncd.service(8),
systemd-networkd.service(8)
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.
This page is part of the systemd (systemd system and service
manager) project. Information about the project can be found at
⟨http://www.freedesktop.org/wiki/Software/systemd⟩. If you have
a bug report for this manual page, see
⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
This page was obtained from the project's upstream Git repository
⟨https://github.com/systemd/systemd.git⟩ on 2024-06-14. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
systemd 257~devel TIMESYNCD.CONF(5)
Pages that refer to this page: systemd.directives(7), systemd.index(7), systemd.syntax(7), systemd-timesyncd.service(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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