hwclock

[Bruce Dubbs]

I believe there was some discussion of setting the system clock via udev a while 
back, but I can't find the thread right now.

I had a short email conversation with the util-linux-ng maintainer about putting 
/etc/adjtime in /var/lib like is done in LFS.  He asked about the timing of 
mounting partitions (S40mountfs for us) and running hwclock (S25setclock for us).

We moved setclock from S60 to S25 about a year ago:

http://wiki.linuxfromscratch.org/lfs/ticket/1948

We modify the code to make the default location of adjtime to be /var/lib, but 
we don't warn about making /var a separate partition.  If that is done, hwclock 
will not be able to save it's drift adjustment parameters.   It may be a non 
issue for us because I haven't heard anyone complain and the error message 
should be in the logs.

If we use udev to set the clock, we may get into a race problem with certain 
configurations.

I don't know if this is worth spending a lot of time, but I'd like to see a 
system that can have / mounted read only.  The problem areas during boot are 
/etc/mtab, /etc/blkid.tab, and /etc/adjtime.  With the move of libblkid and 
libuuid to util-linux-ng, the first two are being addressed in the relatively 
near future, but we should get adjtime right for any reasonable configuration.

   -- Bruce