On May 16, 2015, at 12:58 PM, Rick Thomas <rbtho...@pobox.com> wrote:
>
> On May 16, 2015, at 6:02 AM, Ben Hutchings <b...@decadent.org.uk> wrote:
>
>> This is not implemented directly by the init system. util-linux
>> installs the script/lib/udev/hwclock-set and a udev rule that runs it
>> for each RTC device. However, the hwclock-set script does nothing if
>> systemd is running.
>
> curiouser and curiouser…
>
> Looking at the code in /lib/udev/hwclock-set, I can’t see that it would would
> ever do anything useful (except by chance) in the case like mine where there
> are two rtc devices, only one of which should actually be used to set system
> time at boot.
>
> In particular, it goes to some effort to source /etc/default/rcS and
> /etc/default/hwclock, but it pays no attention to the HCTOSYS_DEVICE
> parameter.
>
> It appears to set the system time from each RTC device in turn as it
> discovers them. So system time ends up set by the last RTC to be discovered.
> If the right one happens to be last, that’s good. But that’s not guaranteed.
Looking further, I find that what I said is not quite true. hwclock-set only
gets called for /dev/rtc0, i.e. the *first* one to be discovered. This happens
in /lib/udev/rules.d/85-hwclock.rules. There is provision in
/lib/udev/rules.d/50-udev-default.rules to swing the /dev/rtc symlink to the
device that has ATTR{hctosys}==“1”, but that doesn’t fix the problem at hand,
because the symlink is not used anywhere in hwclock-set.
Fascinating!
Rick
--
To UNSUBSCRIBE, email to debian-kernel-requ...@lists.debian.org
with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
Archive: https://lists.debian.org/c4618e4b-58a9-4f5d-8cbd-7967f1a9c...@pobox.com
