[ntp:questions] ntpd -g option : does it do what it claims?
mjlee at mindless.com
Tue May 12 01:15:02 UTC 2009
The ntpd man page says:
-g Normally, ntpd exits if the offset exceeds the sanity limit,
which is 1000 s by default. If the sanity limit is set to
zero, no sanity checking is performed and any offset is
acceptable. This option overrides the limit and allows the
time to be set to any value without restriction; however, this
can happen only once. After that, ntpd will exit if the
limit is exceeded. This option can be used with the -q
So, I was running "ntpd -g" on a system using gpsd/shm. It was booting up with the clock set to 1980.
After many hours trying to find out why ntpd was never sychronising my clock to the gpsd time, I found a check in the ntpd source code that ignores any reference timestamps that are more than 4 hours different to the current system clock.
Is the explanation of "-g" option given above incorrect? Based on what it says above, ntpd -g should have been able to correct my clock that was off by 29 years.
Maybe I've misunderstood the purpose of -g ??
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