On 3 Jul 2012, at 12:07, myron wrote:
On Jul 3, 2012, at 11:52 AM, Ralf Hildebrandt wrote:
* myron <kowal...@cs.moravian.edu>:
This morning I came in to find no new mail in my inbox. I ended up
reboot the server. These were the log entries that seem to indicate
when and the
problem was. I checked the time on the server and it was not off at
all. Can someone suggest from these entries what the problem was?
Jul 2 20:52:11 errol dovecot: dovecot: Fatal: Time just moved
backwards by 9 seconds. This might cause a lot of problems, so I'll
just kill myself now. http://wiki.dovecot.org/TimeMovedBackwards
Dovevot killed itself because the time moved backwards by 9 seconds.
BTW: why? Use NTP!
FWIW, using NTP (badly) can be the proximate cause of such a backwards
jump. It's probably the most common one behind a human manually changing
the system time. An unregulated clock chip jumping backwards is
definitionally defective.
I am (was) using ntp. I don't know why the time moved backwards. It
wasn't when I checked the time before rebooting.
root@errol:/var/log# ps -ef | grep ntpd
ntp 1049 1 0 08:25 ? 00:00:00 /usr/sbin/ntpd -p
/var/run/ntpd.pid -g -u 107:116
root 4457 1996 0 12:03 pts/0 00:00:00 grep --color=auto ntpd
running ntpd != functional ntpd.
It used to be that firewalls and trivial configurations were the most
common causes of NTP running without actually keeping the system clock
stable and accurate. These days it is more common for virtualization to
be the cause of trouble which can be highly opaque. Subjectively, I have
also been convinced that server RTC chips have had a huge drop in
accuracy and stability in the past decade, causing the drift assumptions
in traditionally good-enough ntpd configurations to break down. It also
doesn't help that apparently a lot of software can't handle leap
seconds, and that caused lots of trouble at 00:00 GMT 7/1.
A deep discussion of solid time synch would be off-topic, but as you can
see it is absolutely critical when using Dovecot SASL to either solve
the time synch problem or catch the well-documented failure mode of
Dovecot shooting itself in the head to avoid doing bad things.
