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

[Andrey Borzenkov <arvidjaar@gmail.com>]

В Fri, 2 May 2014 15:23:30 +0100
Colin Watson <cjwatson@ubuntu.com> пишет:

> 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.
> 

Note Debian Bug#747653 which results exactly from this behavior - btrfs
which spans multiple LVM volumes; grub hits LVM and does not use UUID
which results in passing multiple devices as root= argument.


> 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,
>