Re: [DNG] booting old system on a different partition

[Rob Owens]

- Original Message -
> From: "Peter Olson" 

> So, I installed the Devuan beta a few days ago and it is great, rather it 
> almost
> mostly works.  I probably need an audio driver installed.  I want to see what
> the old system had installed.
> 
> So I cleared out another partition and moved the backup of my Debian 8.3 onto
> it.  Ran update-grub, which found the backup in its new location.
> 
> But, when I try to boot it grub is confused and is pinned to the old UUID of 
> the
> root filesystem.  (I have already updated /etc/fstab in the restored backup, 
> but
> it is not even getting that far.)  It just dumps me into busybox saying it 
> can't
> find the root fs.  Gotta love grub, which is useful only when nothing is wrong
> :-)
> 
> Any advice about how to proceed?
> 
If the other advice you got does not work, download super grub2 disk and boot 
from
that.  It will find all your bootable OS's.

http://www.supergrubdisk.org/super-grub2-disk/
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Re: [DNG] booting old system on a different partition

[Simon Hobson]

Peter Olson  wrote:

> So I cleared out another partition and moved the backup of my Debian 8.3 onto
> it.  Ran update-grub, which found the backup in its new location.
> 
> But, when I try to boot it grub is confused and is pinned to the old UUID of 
> the
> root filesystem.  (I have already updated /etc/fstab in the restored backup, 
> but
> it is not even getting that far.)  It just dumps me into busybox saying it 
> can't
> find the root fs.

From there, it should, if you know the magic incantation, be possible to 
manually mount the root fs etc and then continue. I don't know the magic 
incantation - perhaps ${pref_search_engine} will help.

But from a step back, at the grub menu, you can opt to edit (it's not 
persistent) the config - so you go and replace "root= " with 
"root=sdxn" which should allow it to boot.
Or, you can boot your normal system, list the UUID, write it down, and edit it 
into the grub config at boot time.

All this is why I much prefer filesystem labels (you can put 
"root=LABEL=oldroot" in the grub config to boot it) - and it's annoying that 
(at least in Debian) the only options are UIDs or device names.

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Re: [DNG] booting old system on a different partition

[Boruch Baum]

On 2016-05-09 00:18, Peter Olson wrote:
> So, I installed the Devuan beta a few days ago and it is great, rather it 
> almost
> mostly works.  I probably need an audio driver installed.  I want to see what
> the old system had installed.
> 
> So I cleared out another partition and moved the backup of my Debian 8.3 onto
> it.  Ran update-grub, which found the backup in its new location.
> 
> But, when I try to boot it grub is confused and is pinned to the old UUID of 
> the
> root filesystem.  (I have already updated /etc/fstab in the restored backup, 
> but
> it is not even getting that far.)  It just dumps me into busybox saying it 
> can't
> find the root fs.  Gotta love grub, which is useful only when nothing is wrong
> :-)
> 
> Any advice about how to proceed?
> 
> Peter Olson

And, just a reminder of this last step:

code:
  update-grub # again

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Re: [DNG] booting old system on a different partition

[Boruch Baum]

On 2016-05-09 00:18, Peter Olson wrote:
> So, I installed the Devuan beta a few days ago and it is great, rather it 
> almost
> mostly works.  I probably need an audio driver installed.  I want to see what
> the old system had installed.
> 
> So I cleared out another partition and moved the backup of my Debian 8.3 onto
> it.  Ran update-grub, which found the backup in its new location.
> 
> But, when I try to boot it grub is confused and is pinned to the old UUID of 
> the
> root filesystem.  (I have already updated /etc/fstab in the restored backup, 
> but
> it is not even getting that far.)  It just dumps me into busybox saying it 
> can't
> find the root fs.  Gotta love grub, which is useful only when nothing is wrong
> :-)
> 
> Any advice about how to proceed?
> 
> Peter Olson

Have you verified that you have a new UUID for that old backed-up
partitiion. IIRC, when one backs up a partition using 'dd
if=/dev/sd{n}{x}', the old UUID is part of the data backed up.

code:
  ls -l /dev/disk/by-uuid

If my guess is correct, for a hypothetical partition sdz9, your fix
should be something like:

code:
  tune2fs /dev/sdz9 -U $(uuidgen)


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[DNG] booting old system on a different partition

[Peter Olson]

So, I installed the Devuan beta a few days ago and it is great, rather it almost
mostly works.  I probably need an audio driver installed.  I want to see what
the old system had installed.

So I cleared out another partition and moved the backup of my Debian 8.3 onto
it.  Ran update-grub, which found the backup in its new location.

But, when I try to boot it grub is confused and is pinned to the old UUID of the
root filesystem.  (I have already updated /etc/fstab in the restored backup, but
it is not even getting that far.)  It just dumps me into busybox saying it can't
find the root fs.  Gotta love grub, which is useful only when nothing is wrong
:-)

Any advice about how to proceed?

Peter Olson
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