ntpd configutration -- a small suggestion from the peanut gallery
matthew at FreeBSD.org
Thu Jun 6 16:35:40 UTC 2019
On 05/06/2019 20:42, Ronald F. Guilmette wrote:
>> Anyway, even if it seems to work now, I'd check if your time is based on localtime or
>> GMT. It's recommended to use GMT, I never use localtime personally.
> For me, I prefer local time. When I type "date" I don't really give a
> flying fig what time it is in London. I'm in California.
That's not actually the effect removing /etc/wall_cmos_clock has.
Without /etc/wall_cmos_clock, the internal system clock is simply
synchronized to the cmos clock at boot, and the cmos clock is synched
back from the system clock at intervals when the system is running and
on shutdown. The cmos clock is the small, fairly cheap but not
astonishingly accurate clock that runs off the battery on your
motherboard, even when your machine is completely unplugged from the
power, while the system clock is the kernel's idea of the current time
based on a rather more accurate reference frequency generated from a
quartz crystal resonator -- and that depends on the system being up and
running to function.
Now, Unix-oid systems generally run their system clock in UTC. They
then calculate the time-of-day you see displayed in your shell by
applying the appropriate offset calculated from the timezone setting --
either derived from /etc/localtime or from setting TZ in your
environment. Windows runs the system clock as the local wall clock time
-- or at least, it used to. No idea if that's still the case or not.
The advantage of the Unix way is that each different user, or even each
different process, can easily run with a different timezone setting.
The effect of /etc/wall_cmos_clock is to tell the kernel to apply the
timezone offset when it either updates the cmos clock, or updates the
system clock from it. Basically it's a hack to support dual-booting
between Windows and FreeBSD, and if you never want to do that then your
best choice is simply to keep cmos and system clocks synchronized on UTC
so that there's no offset to calculate.
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