There is a wonderful net standard called NTP that can synchronize system clocks. You may already have followed someone's advice and used 'ntpdate' or 'rdate' to set the time on your server. But NTP is really designed to keep a large network of clocks perfectly synchronized. Not just accurate to the second, but to the millisecond! Here's how to set it up.

First, make sure you have some kind of firewall running. This is generic information really, not specific to NTP, but you should always run a firewall if you have a publically available server. In this case, it may protect you from yet-undiscovered flaws in your NTP client.

Now to properly use NTP, you need to have the full set of NTP tools. You may already have them installed; you can check by running the following as root:

rpm -q ntp

If it says it is not installed, then you need to download and install the appropriate RPMs. Head over to http://www.rpmfind.net/linux/rpm2html/search.php?query=ntp and find the right package for your operating system. Download the RPM, and install it as root:

rpm -ivh ntp-*.rpm


Now, you have to configure it. I've done all the hard work and found some reliable servers with open access policies ... all you have to do is copy my files!

You need to edit your /etc/ntp.conf file and REPLACE the contents with the following:


restrict default nomodify notrap noquery
restrict 127.0.0.1
server now.okstate.edu
server clock.nyc.he.net
server clock.via.net
server ntp-2.vt.edu
server 127.127.1.0 # local clock
fudge 127.127.1.0 stratum 10
driftfile /etc/ntp/drift


Also edit your /etc/ntp/step-tickers file and REPLACE the contents with:


now.okstate.edu
clock.nyc.he.net
clock.via.net
ntp-2.vt.edu



Now run the following:

chkconfig --level 345 ntpd on
service ntpd restart


And you're all done! The ntpd program is running in the background, accurately keeping time down to the millisecond, with absolutely no drift. Your clock will always be accurate!

not good enough. I want mine close to one millionth of a second!

only joking but couldnt resist saying it!

thanks for this thread, i know about the time feature, but wanted to learn more info on it.

implemented except for...

chkconfig --level 345 ntpd on
service ntpd restart

commands not found....

suppose it will start on next system startup the same as already preconfigured as remmed...

thanks for the info
c.klemp

if i may ask

what is the purpose of letting your time accurate . what would i loose if its not ???

dead will rise from their graves and sun will disapper for the next 23 years.


:)

Nothing, you will just have non accurate system clock

Thanks Doggy forthis information, I have used it on my server because I use a lot of cron jobs and want to keep the time acurate.

Just a quick notice, you can use pool.ntp.org to fetch random servers instead of pointing to single hosts. Check ntp.org for more informations. I have it working on my network and it works like a charm :)

Originally posted by naguib2000
if i may ask

what is the purpose of letting your time accurate . what would i loose if its not ???

In a single-server enviroment where there is only one clock it's not so important, but when you start sharing files across servers, use more than one server to host a site (i.e. server farm or primary/fallover), or have separate subsystems for mail/database, etc. it becomes quite important.

Originally posted by VisiGod
Just a quick notice, you can use pool.ntp.org to fetch random servers instead of pointing to single hosts. Check ntp.org for more informations. I have it working on my network and it works like a charm :)

Thanks for the tips! I usually use the ntp.nasa.gov server and it's been rock solid.

I looked at the download options for the tools but I couldnt see an option for centos, can it be done for this os?