Next, define the rules that will allow clients to connect to your service ( localhost is considered a client too) using the restrict command you should already have a line like this in your file: If setting up an NTP server, check that you have orphan mode enabled, so that, in case it loses internet access, it will continue serving time to the network enable orphan mode using the tos configuration parameter (you can set up to stratum 15) so that it will never be used unless internet access is lost: The burst option always does this, even on the first attempt, and should never be used without explicit permission and may result in blacklisting. The iburst option is recommended, and sends a burst of packets only if it cannot obtain a connection with the first attempt. if you want to use your country's servers with an option: Since ntp version 4.2.7.p465-2, Arch Linux uses its own default vendor pool of NTP servers provided by the NTP Pool Project (see FS#41700). Typically, stratum 2 servers are used for general synchronization purposes: if you do not already know the servers you are going to connect to, you should choose a server pool close to your location from the servers ( alternative link). It has to be understood that a server's stratum cannot be taken as an indication of its accuracy or reliability. NTP servers are classified in a hierarchical system with many levels called strata: the devices which are considered independent time sources are classified as stratum 0 sources the servers directly connected to stratum 0 devices are classified as stratum 1 sources servers connected to stratum 1 sources are then classified as stratum 2 sources and so on. The main daemon is ntpd, which is configured in /etc/ntp.conf. For server configuration, see #NTP server mode. You can skip to #Usage if you want to use the Arch Linux default configuration file for it.

By default, ntpd works in client mode without further configuration. See System time#Time synchronization for other NTP implementations. This article further describes how to set up and run the NTP daemon, both as a client and as a server. The NTP Project provides a reference implementation of the protocol called simply NTP. The accuracy on local area networks is even better, up to one millisecond. It is designed to mitigate the effects of variable network latency and can usually maintain time to within tens of milliseconds over the public Internet. Network Time Protocol is the most common method to synchronize the software clock of a GNU/Linux system with internet time servers.

Online time clock server