[PATCH] Fix root device detection for lvm2

[PATCH] Fix root device detection for lvm2

[sean finney]

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If you have a single / filesystem on lvm2, the boot process will hang
waiting for a root filesystem that never appears.  This patch modifies
the logic in deciding what the root device actually is, and allows the
initramfs to succesfully load the root filesystem.

The attached patch has been in use in the debian "grub2" packages for
quite a while, so I assume it's safe to use :)

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Index: b/util/grub.d/10_linux.in
===================================================================
--- a/util/grub.d/10_linux.in
+++ b/util/grub.d/10_linux.in
@@ -43,7 +43,8 @@
 esac
 
 if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
-    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ; then
+    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+    || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm"  ] ; then
   LINUX_ROOT_DEVICE=${GRUB_DEVICE}
 else
   LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}

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Re: [PATCH] Fix root device detection for lvm2

[Vladimir 'φ-coder/phcoder' Serbinenko]

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On 06/02/2010 09:07 PM, sean finney wrote:
> Index: b/util/grub.d/10_linux.in
> ===================================================================
> --- a/util/grub.d/10_linux.in
> +++ b/util/grub.d/10_linux.in
> @@ -43,7 +43,8 @@
>  esac
>  
>  if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
> -    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ; then
> +    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
> +    || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm"  ] ; then
>    LINUX_ROOT_DEVICE=${GRUB_DEVICE}
>  else
>    LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
>   
Applied with some chages. Thanks

-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: [PATCH] Fix root device detection for lvm2

[Colin Watson]

On Thu, Jul 01, 2010 at 11:25:00PM +0200, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 06/02/2010 09:07 PM, sean finney wrote:
> > Index: b/util/grub.d/10_linux.in
> > ===================================================================
> > --- a/util/grub.d/10_linux.in
> > +++ b/util/grub.d/10_linux.in
> > @@ -43,7 +43,8 @@
> >  esac
> >  
> >  if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
> > -    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ; then
> > +    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
> > +    || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm"  ] ; then
> >    LINUX_ROOT_DEVICE=${GRUB_DEVICE}
> >  else
> >    LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
> 
> Applied with some chages. Thanks

The changes seem to have been to simplify the test to:

  [ "x`grub-probe -t abstraction --device ${GRUB_DEVICE}`" = "xlvm"  ]

Unfortunately this is an incorrect simplification.  grub-probe can print
multiple abstractions, and does in the case of e.g. LVM on RAID.  If it
is correct to avoid UUIDs for plain LVM, it is also correct to avoid
them for LVM on RAID.

-- 
Colin Watson                                       [cjwatson@ubuntu.com]

Re: [PATCH] Fix root device detection for lvm2

[Vladimir 'φ-coder/phcoder' Serbinenko]

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On 07/02/2010 01:32 AM, Colin Watson wrote:
> On Thu, Jul 01, 2010 at 11:25:00PM +0200, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
>   
>> On 06/02/2010 09:07 PM, sean finney wrote:
>>     
>>> Index: b/util/grub.d/10_linux.in
>>> ===================================================================
>>> --- a/util/grub.d/10_linux.in
>>> +++ b/util/grub.d/10_linux.in
>>> @@ -43,7 +43,8 @@
>>>  esac
>>>  
>>>  if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
>>> -    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" ; then
>>> +    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
>>> +    || [ "`grub-probe -t abstraction --device ${GRUB_DEVICE} | sed -e 's,.*\(lvm\).*,\1,'`" = "lvm"  ] ; then
>>>    LINUX_ROOT_DEVICE=${GRUB_DEVICE}
>>>  else
>>>    LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
>>>       
>> Applied with some chages. Thanks
>>     
> The changes seem to have been to simplify the test to:
>
>   [ "x`grub-probe -t abstraction --device ${GRUB_DEVICE}`" = "xlvm"  ]
>
> Unfortunately this is an incorrect simplification.  grub-probe can print
> multiple abstractions, and does in the case of e.g. LVM on RAID.  If it
> is correct to avoid UUIDs for plain LVM, it is also correct to avoid
> them for LVM on RAID.
>
>   
Ok I agree. The problem with original patch was that it would accept
ttttlvmuuu too. Feel free to fix.


-- 
Regards
Vladimir 'φ-coder/phcoder' Serbinenko



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Re: [PATCH] Fix root device detection for lvm2

[Colin Watson]

On Fri, Jul 02, 2010 at 01:44:21AM +0200, Vladimir 'φ-coder/phcoder' Serbinenko wrote:
> On 07/02/2010 01:32 AM, Colin Watson wrote:
> > The changes seem to have been to simplify the test to:
> >
> >   [ "x`grub-probe -t abstraction --device ${GRUB_DEVICE}`" = "xlvm"  ]
> >
> > Unfortunately this is an incorrect simplification.  grub-probe can print
> > multiple abstractions, and does in the case of e.g. LVM on RAID.  If it
> > is correct to avoid UUIDs for plain LVM, it is also correct to avoid
> > them for LVM on RAID.
> 
> Ok I agree. The problem with original patch was that it would accept
> ttttlvmuuu too. Feel free to fix.

Fair enough.  Done (r2503).

-- 
Colin Watson                                       [cjwatson@ubuntu.com]