Preventing ntpd from adjusting time (backwards)
mel.flynn+fbsd.questions at mailing.thruhere.net
Tue Apr 21 18:58:02 UTC 2009
On Tuesday 21 April 2009 19:43:30 Chuck Swiger wrote:
> Hi, Mel--
> On Apr 21, 2009, at 2:06 AM, Mel Flynn wrote:
> > Some coarse reading of ntpd(8) and ntp.conf(5) doesn't lead me to
> > believe it's
> > possible to make ntpd *not* adjust the time. With adjust I don't
> > mean the skew
> > operation, but really change the time.
> Perhaps I've missed it elsewhere in this thread, but I don't believe
> anyone actually answered the original question, which would be to use:
> -x, --slew
> Slew up to 600 seconds.
> Normally, the time is slewed if the offset is less than the
> threshold, which is 128 ms by default, and stepped if
> above the
> threshold. This option sets the threshold to 600 s,
> which is
> well within the accuracy window to set the clock
Hmm, that might work. Thanks!
> It should be surprising that your clock would jump by 6 seconds. Do
> you have adequate upstream timesources (ie, at least 4) configured, is
> your local HW clock busted somehow, or are you doing something odd
> with power-savings mode or running in a VM or something...?
One timesource, shared on local network, this machine is a client of the
gateway, which uses only one source (ntp.alaska.edu, which is geographically
10 minutes by car but thanks to Alaska bad peering, we go through Seattle
anyway). I checked the logs, that machine didn't step at all that day (or any
other day, as far as my logs go). It always happens after reboot, as Matthew
indicated. No VM, no power-savings. The only odd things are Hyperthreading and
Well, I abuse the machine quite heavily from time to time, but then I'd expect
the clock to be slow, not 6 seconds faster.
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