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  1. #1
    Join Date
    Oct 2003
    Location
    Portugal
    Posts
    77

    HOW-TO: use NTP to keep your system clock accurate to one thousandth of a second

    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/rpm2htm....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:

    PHP Code:
    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:

    PHP Code:
    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!

  2. #2
    Join Date
    May 2004
    Posts
    119
    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.

  3. #3
    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

  4. #4
    Join Date
    May 2004
    Posts
    66
    if i may ask

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

  5. #5
    Join Date
    Jan 2001
    Location
    Vienna, Austria
    Posts
    2,531
    dead will rise from their graves and sun will disapper for the next 23 years.




    Nothing, you will just have non accurate system clock

  6. #6
    Join Date
    Aug 2004
    Posts
    49
    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.

  7. #7
    Join Date
    Jun 2003
    Location
    Portugal
    Posts
    31
    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

  8. #8
    Join Date
    Mar 2005
    Location
    Cardiff, Wales, UK
    Posts
    46
    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.
    Jonathan Wright (Technical Director, JAB Web Solutions Limited).

    UK Hosting and Reseller Hosting from JAB Web Solutions

  9. #9
    Join Date
    Oct 2004
    Posts
    305
    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.

  10. #10
    Join Date
    Feb 2001
    Location
    UK
    Posts
    461

    Centos?

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

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