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Re: Grub installation may get erroneous after a hardware reconfiguration

From: Vladimir 'φ-coder/phcoder' Serbinenko
Subject: Re: Grub installation may get erroneous after a hardware reconfiguration
Date: Tue, 19 Mar 2013 07:50:04 +0100
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Keep list CC'ed
On 18.03.2013 23:50, Arbiel (gmx) wrote:

> Hi
> Le 14/03/2013 18:59, Vladimir 'φ-coder/phcoder' Serbinenko a écrit :
>> On 14.03.2013 16:26, Arbiel (gmx) wrote:
>>> Hi
>>> The grub installation procedure should make no assumption regarding the
>>> eventual runtime configuration concerning device and file references.
>>> 1) grub.cfg file contains "set root=.." instructions which refer to
>>> partitions which are present at installation time, but could be absent
>>> at runtime. These instructions may cause grub to stop booting,
>>> displaying a message "No such device", and are of no use as they are
>>> followed by "seach --set=root ... " instructions which set root
>>> according to the runtime configuration.
>>> Please, remove these "set root=.." instructions.
>> As long as search has found the right device, the value of root is
>> overridden. If it didn't work the problem is somewhere else. The
>> usefulness of these lines is for bw-compatibility mainly.
> The issue is not with the "search" instructions which, as you say,
> overwrite the value set by the preceding "set root=(hd....)"
> instructions. The issue is with these "set root=(hd,...) instructions
> which can refer to an inexistant device,

Not a problem since no file is referenced without explicit drive between
these instructions

> because the running
> configuration is not what the installation configuration was. In that
> case, grub displays a "No such device" message and stops the booting
> procedure.

If you see any such problem, it's caused by a bug somewhere else, not
the set root statement. You write a lot about how to fix an issue you
haven't even really shown to exist. Please provide a replication
instructions with VM and recent bzr checkout

>>> 2) grub now embeds a little file to properly set the root variable when
>>> core.img and grub/grub.cfg do not reside on the same partition. Such a
>>> file should also be embedded even when both core.img and grub/grub.cfg
>>> reside on the same partition, as the reference to this partition may get
>>> illegal at runtime. No one knows whether or not the destination drive
>>> has been ported away to another configuration, where its address differs
>>> from what it was at installation time.
>> Only the partition number is stored, not the drive. And partition number
>> doesn't change on disk move
>>> Please always embed a file to properly set root, prefix and
>>> config_directory.
> A recent boot-repair report showed the embedding of a 2 line grub shell
> file to properly set the root variable to a device refered to by its
> UUID. However, the inclusion may have been the result of the use
> gub-mkimage command inside the installation procedure. So, the issue may
> be to be reported to Ubiquity, the software responsible for Ubuntu
> distributions installation. So forget about my request.

UUIDs are used for cross-disk installation. Partition numbers on
single-disk ones. In any case neither changes after swapping disks

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