The keys and key identifiers must match in both the client and server key files.The default is to disable the authentication function.There are multiple tiers of NTP servers, with the tier one NTP servers connected to atomic clocks (often via GPS), and tier two and three servers spreading the load of actually handling requests across the internet.The client software is a lot more complex than you might think as it has to factor communication delays, and adjust the time in a way that does not affect the other processes that run on the system.The tutorial below is applicable to both of them and can be used in any DE, even without an X server. Network Time Protocol (NTP) is a UDP/IP protocol for synchronizing time over a network connection.
The good news is the functionality originally intended for this program is available in the sets the local date and time by polling the Network Time Protocol (NTP) server(s) given as the server arguments to determine the correct time. A number of samples are obtained from each of the servers specified and a subset of the NTP clock filter and selection algorithms are applied to select the best of these.
However, a system's clock is likely to drift considerably between reboots if the time between reboots is long.
In that case it makes sense to correct the time occasionally.
Note that the accuracy and reliability of can be run manually as necessary to set the host clock, or it can be run from the host startup script to set the clock at boot time.
This is useful in some cases to set the clock initially before starting the NTP daemon Enable the authentication function and specify the key identifier to be used for authentication as the argument key.