Re: Time server...how to set it up on FC1?
From: Rodolfo J. Paiz (rpaiz_at_simpaticus.com)
Date: Mon, 12 Apr 2004 17:27:32 -0600 To: For users of Fedora Core releases <firstname.lastname@example.org>
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
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.
-- Rodolfo J. Paiz email@example.com http://www.simpaticus.com -- fedora-list mailing list firstname.lastname@example.org To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list