On Fri, Apr 23, 2004 at 01:13:11PM +0100, Jez Hancock wrote: > On Fri, Apr 23, 2004 at 09:04:56AM +0300, hugle wrote: > > > SOmetimes I see such messages in dmesg. > > > > perl# dmesg > > uptime() went backwards (1574174.333073 -> 1573478.944788) > > > > what they mean? and what causes them to appear ? > > is it good or bad?? :) > > I'd always presumed these messages occured on my machine because the > ntpd (network time protocol daemon) had adjusted the system clock. I > can't actually tell you for sure since the messages aren't logged by > syslog here so there's no easy way of comparing the times to see if they > correspond to the ntpd adjustments. > > Check to see if you have ntpd running - if so that's probably the reason > for the messages.
Actually, that shouldn't happen because of ntpd(8). If ntpd detects that your system clock is fast, it will make it run slightly slower until it gradually comes back into synch. It shouldn't ever jump the system clock to the right time during normal operation, neither should it ever cause the system clock to run backwards. Of course, there is an exception: right after boot, it's usual to run ntpdate(8), and fairly common to run that with the '-b' flag so that the time gets stepped straight to the correct value. The ntpd developers have marked ntpdate for eventual retirement and have rolled its functionality into the main ntpd(8) -- so 'ntpq -q' is meant to be functionally equivalent to ntpdate. Even so, it's not clear to me that the 'step the clock' mode of operation is available from 'ntpd -q'. The OP's original query about 'microuptime went backwards' is something that has come up fairly frequently on various mailing lists. Googling for that message returns a few hundred hits. There has been quite a lot of effort to eradicate it, but apparently not with complete success yet. Most of the time it was apparently due to problems with apm on certain hardware, but it could be caused by other factors. With the switch to APCI in 5.x there have been far fewer reports of these errors appearing. Usually this is pretty innocuous. If you're only getting these messages occasionally, then you can probably just ignore them. On the other hand, if you've suddenly started to get floods of these messages for no apparent reason, it may possibly indicate that you have hardware which is starting to get a bit marginal. Keep the system under observation, backup religiously and check the log messages for clues regularly. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way PGP: http://www.infracaninophile.co.uk/pgpkey Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK
Description: PGP signature