Configuring the Network Time Protocol (NTP)

The NTP configuration file

The configuration file /etc/ntp.conf contains information that the ntpd daemon uses at startup, including:

What are the possible hosts with which to synchronize.
How to select the host with which to synchronize.
What restrictions exist on other hosts communicating with the local host.
Whether or not to broadcast NTP packets on the local network.
Whether or not to listen for broadcast NTP packets.
What the roundtrip delay is between the local host and the host on this network (if any) that is broadcasting NTP packets.
Where the driftfile is located.
Whether or not to monitor NTP connections.
Whether or not to allow runtime reconfiguration of the local host.

The syntax of the configuration file is fairly free format. Comments begin with a ``#'' character and extend to the end of the line. Comments may be inserted freely and blank lines are ignored. Configuration statements include an initial keyword followed by arguments that are separated by white space (blanks or tabs). These statements may not be split over multiple lines. A list of the configuration statements with their arguments appears below. Optional arguments are delimited by ``['' and ``]'', and alternatives are separated by ``|''.