[lug] Superblock in the future?

David L. Anselmi anselmi at anselmi.us
Fri Dec 30 09:34:06 MST 2005

Marty Haught wrote:
> Ah sure.  Indeed it is.  The hwclock did not mention any timezone
> which would suggest GMT.    Okay so the clock seems fine.  Why would
> the system believe that the Superblock lives in the future?

The hwclock doesn't have a timezone.  In the Windows world it's assumed 
to be local.  In Linux you can tell the kernel that it's UTC or local.

So due to your upgrade your hwclock sense changes from local to UTC. 
You shut down at 2100 UTC.  Your hwclock says 1400 and your superblock 
says 2100 (filesystem times are always UTC).

Now you boot, the kernel reads the hwclock--1400 UTC.  If it read 1400 
local everything would be fine.  But 1400 UTC is earlier than 2100 so it 
complains about your superblock.

The solution, clearly, is to leave your machine off for > 7 hours 
whenever you reboot it.  Or move somewhere east of Greenwich.

This could be caused by a dual boot system (one in UTC, one in local) 
arguing over the clock.  It could also be caused by something stupid in 
the Debian upgrade.  I'll watch when I upgrade this weekend and file a 
bug if necessary.


More information about the LUG mailing list