Re: Why ignore UUID when linux root device is an LV?

[Colin Watson <cjwatson@ubuntu.com>]

On Fri, May 02, 2014 at 02:54:13PM +0200, Sree Harsha Totakura wrote:
> I would like to know why UUID is not used for root device in Linux
> kernel's `root=' parameter when the root device uses LVM.

Filesystem UUIDs on LVM aren't necessarily unique in the presence of
snapshots; and not all initramfses cope with root=UUID=* in any event,
for instance:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=612402

Every time this breaks in GRUB and we end up using UUIDs on LVM again, I
get a slew of Debian bug reports until I figure it out and fix it.

The LVM device names themselves are sufficiently stable that there
should be no need to introduce additional layers of complexity by using
filesystem UUIDs.  In general we only need them in cases where the
device names are not stable.

> >From the commit log:
> > commit 507736c87c49712ac618169d17a659bd6c25eecc
> > Author: Colin Watson <cjwatson@ubuntu.com>
> > Date:   Fri Jul 2 12:32:05 2010 +0100
> > 
> >     * util/grub-mkconfig_lib.in (uses_abstraction): New function.
> >     * util/grub.d/10_linux.in: Use it to check for LVM, so that
> >     LVM-on-RAID is handled correctly.
> 
> I see that this condition is added to address LVM/RAID configurations.
> But, I guess it is similar to LVM/LUKS; is it not?

I'm not sure, but perhaps GRUB_ENABLE_CRYPTODISK=y would help
grub-mkconfig notice this?

Regards,

-- 
Colin Watson                                       [cjwatson@ubuntu.com]