Chrony is an implementation of the Network Time Protocol (NTP). It can
synchronize the system clock with NTP servers, reference clocks (e.g. a
GPS receiver), and manual input using wristwatch and keyboard. It can
also operate as an NTPv4 (RFC 5905) server and peer to provide a time
service to other computers in the network.
Chrony consists of two programs: chronyd and chronyc.
Chronyd is a daemon which runs in the background on the system. It
obtains measurements of the system clock’s offset relative to time
servers on other systems via the network and adjusts the system time
accordingly. For isolated systems, the user can periodically enter the
correct time by hand (using chronyc). In either case, chronyd
determines the rate at which the computer gains or loses time, and
compensates for this. Chronyd can act as either a client or a server.
Chronyc provides a user interface to chronyd for monitoring its
performance and configuring various settings. It can do so while
running on the same computer as the chronyd instance it is controlling
or a different computer.