[Linux-aus] Ubuntu 20.04 resume time problem

[Norberto Meijome]

> With systemd-timesyncd it takes some time to get back to the right time,
> sometimes more than 10 minutes.

Hi,
seeing the obvious/expected fixes have failed, I feel less squeamish to
suggest an exec of ntpdate on wake and after network service is up. I hoped
you could also tweak how aggressively systemd.timesyncd drifts the clock
but its config seems quite minimal (only man page checked though).

good luck,
B

On Wed, 6 Jul 2022 at 17:45, Russell Coker via linux-aus <
linux-aus at lists.linux.org.au> wrote:

> On Tuesday, 28 June 2022 13:30:57 AEST NeilBrown via linux-aus wrote:
> > On Tue, 28 Jun 2022, Russell Coker wrote:
> > > I have a laptop that is dual boot Ubuntu 20.04 and Windows. I've
> > > configured it for "RTC in local TZ" with timedatectl so it can have the
> > > same time as Windows (I'm aware that I could change Windows via regedit
> > > to use UTC for the hwclock but I'm trying to work out the best option
> for
> > > a corporate rollout).  The problem is that I resume from suspend and
> the
> > > system immediately treats the RTC as if it was in UTC thus being out by
> > > 10 hours (time zone +1000).
> > >
> > > How does Ubuntu get the time from the RTC on resume? Any clues as to
> where
> > > to look would be really appreciated. I've done Google searches and
> found
> > > nothing helpful. Even if you just know which program does it that would
> > > help a lot, I could read the source.
> >
> > It isn't up to Ubuntu - the Linux kernel does (or should do) everything
> > needed.
> > Providing the kernel is built with CONFIG_PM_SLEEP and
> > CONFIG_RTC_HCTOSYS_DEVICE, and providing you have RTC hardware with a
> > suitable driver, then on suspend rtc_suspend() in drivers/rtc/class.c
> > will take note of the value stored in the rtc, and on resume
> > rtc_resume() will check what the difference was and update the clock.
> >
> > cat /sys/class/rtc/rtc0/hctosys
> >
> > should show "1" if everythings is configured properly.  In that case it
> > should "just work".
>
> It does show "1" and the kernel build options include those ones you
> specify,
> but unfortunately it doesn't "just work".
>
> NTP the protocol allows fixing this with the systemd-timesyncd
> implementation,
> the ntpd implementation gets unhappy when the time is more than 20 minutes
> out.  With systemd-timesyncd it takes some time to get back to the right
> time,
> sometimes more than 10 minutes.
>
> I have not seen this cause a SSL problem.  When this happens Kerberos is
> no
> more broken than usual (that's another issue I have to solve).
>
> Yes I know that using the local time for the RTC has some downsides, but
> every
> option for dual boot has some downsides.
>
> Thanks for the suggestions.
>
> --
> My Main Blog         http://etbe.coker.com.au/
> My Documents Blog    http://doc.coker.com.au/
>
>
>
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