Ubuntu 14.04 Ultimate Server Guide

Part 2: NTP

Your server will automatically request the time from the Ubuntu NTP servers on every boot… but hopefully you’re not going to reboot it very often. It is useful for the server time to be correct when debugging and it is ESSENTIAL for the server and all the clients on the network to have the same time (±5mins by default) for Kerberos to work.

Fortunately, this is a very easy thing to configure on Ubuntu. Simply install ntpd with:

sudo apt-get install ntp

As of Ubuntu 11.04, a default pool of NTP servers will be used.

# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for
# more information.
server 0.ubuntu.pool.ntp.org
server 1.ubuntu.pool.ntp.org
server 2.ubuntu.pool.ntp.org
server 3.ubuntu.pool.ntp.org

However you can change this by editing /etc/ntp.conf

You should also edit /etc/ntp.conf to allow the local network to use your time server:

 # If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
broadcast 192.168.0.255

References

https://help.ubuntu.com/10.04/serverguide/C/NTP.html