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OpenNTPD (part of the OpenBSD project) is a daemon that can be used to synchronize the system clock to internet time servers using the Network Time Protocol, and can also act as a time server itself if needed. It implements the Simple Network Time Protocol version 4, as described in RFC 5905, and the Network Time Protocol version 3, as described in RFC 1305.


Install the openntpd package. The default configuration is actually usable if all you want is to sync the time of the local computer.


To configure OpenNTPD, you need to edit /etc/ntpd.conf. See ntpd.conf(5) for all available options.

Tip: After configuring, check the configuration file for validity by executing:
$ ntpd -n
Note: HTTPS constraint feature is not supported by openntpd, it requires OpenNTPD to be built with LibreSSL. openntpd is built with OpenSSL.


To sync to a single particular server, uncomment and edit the "server" directive.


The "servers" directive works the same as the "server" directive, however, if the DNS name resolves to multiple IP address, ALL of them will be synced to. The default, "" is working and should be acceptable in most cases. You can find the server's URL in your area at


Any number of "server" or "servers" directives may be used.


If you want the computer you run OpenNTPD on to also be a time server, simply uncomment and edit the "listen" directive.

For example:

listen on *

will listen on all interfaces, and

listen on
listen on ::1

will only listen on the loopback interface.

Your time server will only begin to serve time after it has synchronized itself to a high resolution. This may take hours, or days, depending on the accuracy of your system.


Start OpenNTPD at boot

Enable openntpd.service.

Making openntpd dependent upon network access

If you have intermittent network access (you roam around on a laptop, you use dial-up, etc), it does not make sense to have openntpd running as a system daemon on start up. Here are a few ways you can control openntpd based on the presence of a network connection.

Using NetworkManager dispatcher

OpenNTPD can be brought up/down along with a network connection through the use of NetworkManager's dispatcher scripts.

Install networkmanager-dispatcher-openntpd.

Using wicd

Create these two scripts and mark them executable using chmod.

systemctl start openntpd.service
systemctl stop openntpd.service

Using dhclient hooks

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: hook example needed (Discuss in Talk:OpenNTPD#)

Another possibility is to use dhclient hooks to start and stop openntpd. When dhclient detects a change in state it will run the following scripts:

  • /etc/dhclient-enter-hooks
  • /etc/dhclient-exit-hooks

See dhclient-script(8)

Using dhcpcd hooks

if $if_up; then
	systemctl start openntpd.service
elif $if_down; then
	systemctl stop openntpd.service

See dhcpcd-run-hooks(8)


Error adjusting time

If you find your time set incorrectly and in log you see:

openntpd adjtime failed: Invalid argument


# ntpd -s -d

This is also how you would manually sync your system.

Increasing time shift

Starting openntpd in the background could lead to synchronization errors between the actual time and the time stored on your computer. If you recognize an increasing time difference between your desktop clock and the actual time, try to start the openntpd daemon normal and not in the background.

See also