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NTP is the network time protocol. It allows you to fetch the current date/time from an internet time server. You can also use it to provide a network time service.


Synchronize time

To sync the time with the time server pool.ntp.org use the command

sntp -s no pool.ntp.org

Keep time synchronized

To keep the time synchronized over reboots,

  • sync it one time:
sntp -s no pool.ntp.org 
  • have a file /etc/ntp.conf with one line:
server pool.ntp.org
  • start the NTP service:
/etc/init.d/ntp start
  • configure the NTP service to start on boot, e.g. for SUSE Linux:
chkconfig ntp start

Show time offset from time server

# sntp timeserver.mycompany.com
2014-02-18 10:09:11.391178 (-0100) +6.45592 +/- 0.000427 secs

Means that timeserver.mycompany.com is 6.5 seconds in the future compared to the local clock.

Query status

# /etc/init.d/ntp status
     remote           refid      st t when poll reach   delay   offset  jitter
*timehost1.local .PPS.            1 u  356 1024  377    1.404    0.049   0.154

Checking for network time protocol daemon (NTPD):                    running

Configure it

Edit /etc/ntp.conf, add your time server like this:

server myserver.domain