[RndTbl] strange NTP problem on one of 3 peers
Gilles Detillieux
grdetil at scrc.umanitoba.ca
Wed Apr 25 10:53:41 CDT 2012
I have a weird problem with clock drift that just started to happen
today on one of my Linux systems. I was wondering if someone on the
list has some NTP experience and could help me solve this puzzle.
I have a group of 3 systems operating as peers, and they've been keeping
time well for years. Yesterday I upgraded them from Scientific Linux
5.7 to 5.8 (an RHEL 5.8 clone like CentOS 5.8), and rebooted them to the
latest kernel on SL 5.8, 2.6.18-308.4.1.el5. I rebooted 2 of them
yesterday evening, and the last one I set an at job to reboot at 2:30
am. (It's our mail server so I didn't want to reboot it earlier.) This
morning, I noticed this last system's clock was 4-5 minutes behind the
others. I've stopped ntpd, reset the clock to the correct time, and
restarted ntpd. I've done this twice already this morning, and each
time, the clock starts slowly drifting backwards.
The syslog entries from ntpd in /var/log/messages on the 2 other systems
show fairly frequent occurrences of "synchronized to <IP>, stratum <n>",
where n is usually 2 or 3. But for the mail server with the drifting
clock, the only ntp sync logged this week was at 21:03:03 yesterday.
The last ones before that were April 10 & April 4, i.e. very
irregularly. The oldest log entries I have in /var/log/messages.4 show
more regular syncs (at least 1-2 a day) up to March 31. So it's
possible this problem existed for a while and had nothing to do with the
updates yesterday, but this is the first time the drift got so bad it
drew attention to itself (some file modification times got out of sync
between this server and another system).
I'd appreciate any ideas on how to tackle this problem.
Gilles
--
Gilles R. Detillieux E-mail: <grdetil at scrc.umanitoba.ca>
Spinal Cord Research Centre WWW: http://www.scrc.umanitoba.ca/
Dept. Physiology, U. of Manitoba Winnipeg, MB R3E 0J9 (Canada)
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