Re: Time server...how to set it up on FC1?

From: Rodolfo J. Paiz (rpaiz_at_simpaticus.com)
Date: 04/13/04

  • Next message: Matt Hansen: "Re: ClamAV on Fedora" 
    Date: Mon, 12 Apr 2004 17:27:32 -0600
To: For users of Fedora Core releases <fedora-list@redhat.com>

    At 14:19 4/12/2004, you wrote:
    >Yes and no ntpd is full time and ntpdate only runs until the time is
    >set. They're in essence the same daemon and when ntpdate starts it sees
    >ntpd and shuts itself down.

    Not quite true. "ntpdate" checks the time on an NTP server just once, and
    then forcefully changes the local system time to whatever result it got
    from the server, regardless of what that result was and with no sanity
    checks. If the server is 10 years off from the local system time, the local
    system time *still* gets smacked instantly to match the server. It just
    happens to use the NTP protocol to communicate with an NTP server.

    "ntpd", on the other hand, checks two or more servers initially every 64
    seconds. After several (8 or more, usually) queries, when it feels that it
    has a sufficiently solid idea of what the "correct" time is Out There, it
    begins slowly sliding the local system clock to match that "correct" time
    without making any sudden moves that might confuse local applications
    and/or server processes.

    Also, ntpd provides very high precision, and it will not adjust the system
    clock (it will exit and report an error instead) if the local time if off
    by more than 120 seconds. Given that my server clocks are usually less than
    0.01 seconds away from the "correct" time and that theoretically ntpd is
    capable of maintaining an error of less than 0.0000001 seconds, you can see
    that it considers *two minutes* as an ungodly, horrendous, utterly
    unacceptable misconfiguration.

    If at all possible, one should avoid using ntpdate at all. Simply run ntpd
    on one box, set all others to adjust their time to that server (which also
    uses NTP), and be done with it. After the initial half-hour (approximately)
    startup period, it all "just works" beautifully.

    Cheers, 

    -- 
Rodolfo J. Paiz
rpaiz@simpaticus.com
http://www.simpaticus.com
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