Keeping accurate time on Linux
If you want to be sure that your computer clock is accurate you can configure your system to use NTP (Network Time Protocol), one of the oldest Internet protocols and the industry standard for time synchronisation.
NTP on will synchronise your computer’s clock to a pool of time servers around the world that are official ‘timekeepers’. It is best to choose the closest to you so response time is minimized and to use more than one in case one goes down. There are more than 1.500 servers to choose from, but some areas are better served than others. Many servers on the internet are extremely inaccurate and Internet time references should not be used as a replacement for a dedicated time server.
However, for basic time synchronisation purposes, Internet providers will suffice. The first step should be to select three servers close to you – preferably in your country, or if there aren’t enough, in your ‘zone. Go to ntp home and browse through the tree of zones and servers to select which ones are best for you. The follow these commands to configure:
1. Configure /etc/ntp.conf
Edit this file with a text-editor. Replace
server <example-server-name>
with your servers, such as:
server 0.br.pool.ntp.org
server 1.br.pool.ntp.org
server 2.br.pool.ntp.org
2. Synchronise your clock manually
If your clock is drifting too NTP might refuse to synchronise it, but it can be done manually:
ntpdate 0.br.pool.ntp.org (server name that you choose)
3. Make your ntp daemon executable
chmod +x /etc/rc.d/rc.ntpd
4. Start NTP now without rebooting
Again, a simple command:
/etc/rc.d/rc.ntpd start
