Re: [PATCH] use UUIDs for cross-disk installs (Re: Issue with boot != root and chainloading)

[Robert Millan <rmh@aybabtu.com>]

On Fri, Jul 25, 2008 at 09:08:52PM -0400, Pavel Roskin wrote:
> 
> As for single drive installs, we could also encode the prefix in the
> text form, like "(hd0,5)/boot/grub" and obsolete the numerical partition
> data.  That would make make_install_device() unnecessary.

On single drive installs we don't encode equivalent information;  we set
some variable to 5 and some variable to -1 (or was it -2?) which basicaly
means: "partition 5, drive is the same you used to boot (and bios told
you via %dx)"

If we do that, it could happen that what we see as hd0 in userland is seen
by BIOS as 0x81 -> hd1, hence breakage.

> The only problem is that we should avoid hardcoding the drive.  We need
> a notation for partitions on the boot or the current drive, perhaps by
> removing the drive name e.g. "(,5)/boot/grub"

Ah; well, as explained above we do this already, just in a different way.

> We could also use UUID for single-drive installs and fallback to the
> partition prefix only if UUID is unsupported or the user requests not to
> use UUID.  Then it won't be a big deal if we hardcode the drive.

Based on the rest of your mail I assume the goal you're pursuing here is
deleting make_install_device().  The problem I see is that if you fallback
when UUIDs are unsupported, you still need to have the code to handle the
fallback case, even if it's rarely used.

OTOH, since UUIDs are supported in all major FSs we have, I don't think
it'd be such a big deal if we abort the install when they can't be probed.

But then, this would need to be carefuly discussed IMHO, as it's a more
radical change.

-- 
Robert Millan

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