Ntp

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