Re: NTP dumps Linux, film at 11. [Fwd/FYI]

Theodore Y. Ts'o (
Tue, 1 Dec 1998 22:24:53 -0500

Date: Tue, 01 Dec 1998 20:31:10 -0500
From: "Brandon S. Allbery KF8NH" <>

It was very noticeable. I upgraded the entire cluster (14 machines)
in HH1202 one afternoon; half the machines started gaining time like
mad, the other half lost time like mad. All machines identical,
indeed from the same manufacturing batch as far as I can tell (and
all idle, the spring semester having just ended at the time). Within
15 minutes all of them were outside of the time window the AFS
kaservers were willing to grant them (the usual 5 minutes for
Kerberos) and linux-afs had lost the battle to resync their clocks.
(10 minutes later xntpd was a standard part of our Linux install....)

Fascinating... as I said, I haven't seen this at all, and I've been
using RedHat 5.x quite frequently. The one big difference is (1) I
don't use a 2.0 kernel, and (2) I don't run Linux-AFS. [(2) is related
to (1). :-/ ]

Have you seen systems lose time coherency without running Linux-AFS?
The AFS code attempts to do time synchronization, and I'm wondering if
that's buggy somehow. This sounds very much like a kernel issue, but
you seem to have observed it being tied to RH5, which seems hard to
believe, unless there's some certain RedHat package which you're
installing which is mucking with the time somehow.

I can also ask the people who setup Linux-Athena at MIT if they've ever
seen something like that. Linux-Athena is currently RH 5.0 based, using
Linux-AFS. Since I'm on the SIPB lists, I'd imagine I would have heard
something about this, but it's possible that I might have missed it.

- Ted

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