CentOS Linux install and configure NTP to synchronize the system clock

by nixCraft on May 18, 2007 · 33 comments· last updated at August 20, 2007

Q. How do I install and configure NTP under CentOS Linux 5 server to synchronize the system clock?

A. You can easily install NTP (Network Time Protocol, a means of transmitting time signals over a computer network) using yum command under Redhat or CentOS/Fedora core Linux.

Procedure

Type the following command to install ntp
# yum install ntp
Turn on service
# chkconfig ntpd on
Synchronize the system clock with 0.pool.ntp.org server:
# ntpdate pool.ntp.org
Start the NTP:
# /etc/init.d/ntpd start

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{ 33 comments… read them below or add one }

1 Jose Arellano June 28, 2008 at 5:26 pm

Nice inof, but how do i configure a NTP server? i want to do this with a client and a server… Thanks

2 Vincent February 19, 2009 at 5:39 pm

Thanks, very straight forward.

3 Pentav February 22, 2009 at 9:34 am

This helped me to fix my call of duty world at war server problem.

Thank you.

4 Joe March 5, 2009 at 11:46 pm

Does anyone know how to make it run ntpdate at certain time increments?
Like every hour?
Thanks

5 Vivek Gite March 6, 2009 at 1:07 am: Setup a cronjob.
Reply

6 Spyisra March 10, 2009 at 7:12 am

Good info, very helpful.
Thanks!

7 Muzammil April 23, 2009 at 4:38 am

Thanks, very simple to install and configure. My time is synchronized now.

8 KSK May 28, 2009 at 3:51 am

nice information but please tell me about the client end that how i sync time server with clients

9 Vivek Gite May 28, 2009 at 6:47 am: See: CentOS / Red Hat Configure an NTP Client And Server
Reply

10 Pooyait September 15, 2009 at 4:47 am

thanks man

very nice

11 Kunal January 6, 2010 at 10:19 am

I did ntpdate 0.asia.pool.ntp.org
and now all my servers showing different time. Any idea why
server1 – Wed Jan 6 15:54:10 IST 2010
server2 – Wed Jan 6 15:47:39 IST 2010
server3 – Wed Jan 6 15:58:23 IST 2010

For more infomation – My servers are in India
Thanks in advance

12 JohnFen February 16, 2010 at 9:17 pm

@Kunal,

My guess: You are obtaining your time info from a pool, so each time you synchronize you’re really getting your time form a different server. This shouldn’t matter, but it seems that the different servers in that pool are not synchronized with each other. You could pick a single server out of the pool and synchronize with it directly on each of your servers.

Or, even better, set up your own ntp server, have it synchronize with a quality outside time server, then have the rest of your servers sync up with the time server that you installed. That way, even if there’s an accuracy problem upstream, at least all of your servers will agree with each other.

13 Bahadir February 25, 2010 at 2:44 pm

I have this error:

ntpdate[14060]: step-systime: Operation not permitted

14 Anonymous June 4, 2010 at 11:25 am: This is likely related to the server being a virtual server. It is not possible to sync to ntp in a VPS because the clock is inherited from the hardware that you are hosted on.
I just ran across the same problem.
Reply

15 Matt April 28, 2010 at 6:27 am

Very useful

16 Bajinder May 31, 2010 at 4:17 am

Very Helpful :)

17 Ahmed Jaafar September 1, 2010 at 12:34 am

Replying @Anonymous June 4, 2010

Actually if you mean a Xen VM, you still can have your own independent system clock setting the following sysctl parameter.
sysctl -w xen.independent_wallclock = 1;

And you save it inside /etc/sysctl.conf

18 Jeffrey Roberts October 9, 2011 at 1:10 pm: Thanks for this tip!
Reply

19 Pal Singh October 22, 2010 at 10:06 pm

Thanks you for your instructions.

20 Koviko April 26, 2011 at 1:25 pm

This is exactly what I was looking for. Thank you for this clear post. :)

21 Jimbo May 27, 2011 at 5:58 pm

Thank you this was very helpful!

22 satish July 6, 2011 at 9:44 am

i have configured ntp server on my machine which runs rhel6
but at the client side at the time of ntp setting it giving me error tha
server is note reachable or doesn’t act as a ntp server and also i cant
see the port of ntp is open on my system, will you please help me for this

Thanks

23 zanami July 20, 2011 at 2:09 am

Thanks but setting up / configuriing ntp servers list would be useful also

24 Ruben September 7, 2011 at 6:07 am

Thank you very much, it was exactly as you said.

25 Amin January 4, 2012 at 5:41 pm

Thanks a lot. great howto…

26 seachen March 20, 2012 at 5:45 pm

i am from Malaysia. which server should i use ?

27 ajd May 8, 2012 at 9:26 am

Great post ,, and it works as a charm :) ,, thank you very much

28 Enrique May 30, 2012 at 5:22 pm

Thanks a lot for your concise post.

29 Emil Stoyanov June 11, 2012 at 12:49 pm

The following command will additionally update your hardware clock

hwclock –systohc

30 s.khademi June 12, 2012 at 9:11 pm

Very helpful. Thanks

31 Fred September 3, 2012 at 2:50 pm

You dont need to have an ntp server running in your machine in order to have the time synced, it is as easy as having cron do the syncing with the ‘ntpclient’ command.

32 Ravindra Gohil September 10, 2012 at 5:49 am: Hi Fred,
Could you please share script to sync with ntp server. so that i can run the same as a cron job.
Reply

33 Leon November 25, 2012 at 12:58 am

Thank you much.

CentOS Linux install and configure NTP to synchronize the system clock

Procedure

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