Comment 8 for bug 1410604

The only place known to me that does that is /etc/init.d/hwclock.sh, which is from util-linux. Something similar is also done under upstart from /etc/init/hwclock.conf where hwclock is called with --systz. This quite plausibly opens rtc as well.

However, these two scripts aren't being run at all any more under systemd -- there it would be timedated which accesses /dev/rtc, but I don't see how this is being activated that early (it usually doesn't run at boot at all).

Can you please confirm whether this happens under upstart or systemd? In the latter case, can you please do

   sudo journalctl -b > /tmp/journal.txt

and attach /tmp/journal.txt here? Thanks!