On 08/10/10 15:52, Roland Smith wrote:
On Tue, Aug 10, 2010 at 03:23:29PM +0100, Arthur Chance wrote:
[snip]
Alternatively, before switching to the ahci driver, label all your
partitions and mount them using their labels rather than device names.
This is probably a better idea.
But people should note the difference between
using 'tunefs -L' and 'glabel label'! The latter uses the last section of the
provider to store metadata, so in that case one should _only_ create a
filesystem on the labeled device!
That way the change in device names won't matter. Just be careful of the
gotcha with labelling the root partition.
What do you mean?
Unless you're working from a fixit CD/DVD, if you're labelling an
existing UFS root partition you have to reboot to single user mode to
use "tunefs -L", and then have to reboot again to edit fstab to use the
labelled device and then reboot a third time for the labelled mount to
take effect. If you try to get clever, as I did, and omit the second
reboot by using "mount -uw /" to make fstab editable you wipe out the
partition label, and the final reboot fails miserably, telling you it
can't find /dev/ufs/root (or whatever) to mount the root partition. The
machine then goes into an cycle of rebooting and failing to find the
root filesystem until you fix the problem.
I haven't looked at the source closely, but I'd guess this is because
when / is mounted r/o the kernel caches a copy of its superblock,
"tunefs -L" modifies the superblock on disk, "mount -uw /" doesn't
reread the disk superblock (it was read only, what could possibly have
changed? :-) so the unlabelled superblock remains cached, and the next
reboot writes the unlabelled cached superblock over the labelled disk
superblock on shutdown.
I was stupid enough to make this mistake twice a few months apart, so
now instructions for labelling root partitions are part of my hard copy
notes for when I may not have a machine working well enough to look at
my online notes.
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