ntpd

The ntpd program is an operating system daemon which sets and maintains the system time of day in synchronism with Internet standard time servers. It is a complete implementation of the Network Time Protocol (NTP) version 4, but also retains compatibility with version 3, as defined by RFC 1305, and version 1 and 2, as defined by RFC 1059 and RFC 1119, respectively. ntpd does most computations in 64-bit floating point arithmetic and does relatively clumsy 64-bit fixed point operations only when necessary to preserve the ultimate precision, about 232 picoseconds. While the ultimate precision is not achievable with ordinary workstations and networks of today, it may be required with future gigahertz CPU clocks and gigabit LANs.

Documentation

• man 8 'ntpd' [EN]

Parameters

-4

Force DNS resolution of following host names on the command line to the IPv4 namespace.

-6

Force DNS resolution of following host names on the command line to the IPv6 namespace.

-g

Normally, ntpd exits with a message to the system log if the offset exceeds the panic threshold, which is 1000 s by default. This option allows the time to be set to any value without restriction; however, this can happen only once. If the threshold is exceeded after that, ntpd will exit with a message to the system log.

-n

Don't fork.

-u USER[:GROUP]

Specify a USER, and optionally a GROUP, to switch to.