[ntp:questions] how to force NTP to use GPS
david at ex.djwhome.demon.invalid
Mon Feb 13 22:36:53 UTC 2012
Uwe Klein wrote:
> semi OT ( either OnTopic or OffTopic ;-):
> What happens if I kill ntpd during clock slewing ?
> What happens if I SIGTERM ntpd during clock slewing ?
I don't think you have fully constrained the problem. In some
environments the slew will stop, although I'm not sure whether it will
stop in about a second or when the whole slew finishes.
Without actually reading the code, I'm not sure what will happen when
using the kernel time discipline on a system that supports it.
According to my Linux man pages, kill(2) is Posix, but adjtime(2) is
not, so there can exist Posix compliant systems in which an ntpd
implementation would continue to slew indefinitely if the kill was
sufficiently hard. (adjtimex(2) is Linux only and ntp_adjtime(2) has no
man page and no alias in adjtimex.)
Linux implementations, at least, will retain frequency corrections in
kernel discipline mode and lose them in user space discipline mode.
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