ntp is a time server you can use to synchronize the time across multiple machines connected to it. If you run a bunch of servers and they don’t all sync to the same time server, your logs will be screwy on them, especially if you try to reconstruct a network event using the logs by looking at the time stamp. This howto is done on Debian Wheezy, but will be similar on other distro’s
su apt-get install ntp
Now make sure it’s getting times from the upstream time servers:
ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== y.ns.gin.ntt.ne 22.214.171.124 2 u 1 64 1 22.974 446456. 0.222 x.ns.gin.ntt.ne 126.96.36.199 2 u - 64 1 21.040 446455. 0.536 188.8.131.52 184.108.40.206 2 u 1 64 1 52.064 446456. 1.268 clock1.albyny.i .CDMA. 1 u - 64 1 84.155 446452. 0.168
This means it’s working. Now login to your other machines and use the IP of this NTP server as your time server, and check to see if it worked.