NTP Time Synchronization in Linux

There are tow pen source software related to the NTP in Linux, the first is ntpdate, the second is ntpd. you can install them as following:
Apt-Get installl NTP; Apt-Get install openntpd;
Or emerge NTP; emerge openntpd.

NtpdateCan 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 daemonNtpd. It is also possible to runNtpdateFromCronScript. However, it is important to note thatNtpdateWith contrivedCronScripts is no substitute for the NTP daemon, which uses sophisticated algorithms to maximize accuracy and reliability while minimizing resource use. Finally, sinceNtpdateDoes not discipline the host clock frequency as doesNtpd, The accuracy usingNtpdateIs limited.

TheNtpdProgram 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.NtpdDoes 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.