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CentOS Linux Install and Configure NTP to Synchronize The System Clock

How do I install and configure NTP under CentOS Linux version 5.x or 6.x server to synchronize the system clock?

You can easily install NTP (Network Time Protocol, a means of transmitting time signals over a computer network) using the yum command under Red Hat or CentOS/Fedora Linux server or workstation based systems. You need to install the following packages:
Tutorial details
DifficultyEasy (rss)
Root privilegesYes
RequirementsNTPD server
Estimated completion time5m

  1. ntp : ntpd server which continuously adjusts system time and utilities used to query and configure the ntpd daemon.
  2. ntpdate : Utility to set the date and time via NTP.
  3. ntp-doc : NTP documentation

Procedure: Setup NTPD on CentOS Linux

Open the terminal or login over the ssh session. You must login as as the root user. Type the following yum command to install ntp
# yum install ntp ntpdate ntp-doc

Turn on service, enter:
# chkconfig ntpd on

Synchronize the system clock with 0.pool.ntp.org server (use this command only once or as required):
# ntpdate pool.ntp.org

Start the NTP server. The following will continuously adjusts system time from upstream NTP server. No need to run ntpdate:
# /etc/init.d/ntpd start

Configure ntpd (optional)

Edit /etc/ntp.conf, enter:
# vi /etc/ntp.conf
Set public servers from the pool.ntp.org project:

server 0.rhel.pool.ntp.org
server 1.rhel.pool.ntp.org
server 2.rhel.pool.ntp.org

See this tutorial on how to configure NTPD for LAN based client on RHEL / CentOS Linux for more information.

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{ 39 comments… add one }

  • Jose Arellano June 28, 2008, 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

  • Vincent February 19, 2009, 5:39 pm

    Thanks, very straight forward.

  • Pentav February 22, 2009, 9:34 am

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

    Thank you.

  • Joe March 5, 2009, 11:46 pm

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

  • Spyisra March 10, 2009, 7:12 am

    Good info, very helpful.
    Thanks!

  • Muzammil April 23, 2009, 4:38 am

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

  • KSK May 28, 2009, 3:51 am

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

  • Pooyait September 15, 2009, 4:47 am

    thanks man

    very nice

    • Krishna October 14, 2014, 8:37 am

      is there a way where i can use my own server from which clients should sync time?

  • Kunal January 6, 2010, 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

  • JohnFen February 16, 2010, 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.

  • Bahadir February 25, 2010, 2:44 pm

    I have this error:

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

    • Anonymous June 4, 2010, 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.

  • Matt April 28, 2010, 6:27 am

    Very useful

  • Bajinder May 31, 2010, 4:17 am

    Very Helpful :)

  • Ahmed Jaafar September 1, 2010, 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

    • Jeffrey Roberts October 9, 2011, 1:10 pm

      Thanks for this tip!

  • Pal Singh October 22, 2010, 10:06 pm

    Thanks you for your instructions.

  • Koviko April 26, 2011, 1:25 pm

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

  • Jimbo May 27, 2011, 5:58 pm

    Thank you this was very helpful!

  • satish July 6, 2011, 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

  • zanami July 20, 2011, 2:09 am

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

  • Ruben September 7, 2011, 6:07 am

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

  • Amin January 4, 2012, 5:41 pm

    Thanks a lot. great howto…

  • seachen March 20, 2012, 5:45 pm

    i am from Malaysia. which server should i use ?

  • ajd May 8, 2012, 9:26 am

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

  • Enrique May 30, 2012, 5:22 pm

    Thanks a lot for your concise post.

  • Emil Stoyanov June 11, 2012, 12:49 pm

    The following command will additionally update your hardware clock

    hwclock –systohc

  • s.khademi June 12, 2012, 9:11 pm

    Very helpful. Thanks

  • Fred September 3, 2012, 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.

    • Ravindra Gohil September 10, 2012, 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.

  • Leon November 25, 2012, 12:58 am

    Thank you much.

  • Wellington Torrejais da Silva May 19, 2014, 2:37 pm

    Thanks!!!

  • Buddhi August 13, 2014, 5:53 pm

    Thanks! you saved my day!

  • Carlo October 8, 2014, 8:31 am

    Thank you very much ! Very useful guide.

  • Scott February 12, 2015, 1:54 am

    Hi,

    I’m having a small issue on Fedora 21: when my computer goes to sleep, I lose time synchronization and have to manually restart ntpd when I wake it in order to resync. Any idea how to fix this?

  • Ed June 22, 2015, 10:39 am

    Great tutorial! Thanks so much from Brazil.
    Ed

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