Re: Grub installation may get erroneous after a hardware reconfiguration

[Arbiel (gmx)]

Hi

Enclosed are two numbered files, generated on my own PC.
blkid.numbered, for displaying uuids
grub.cfg.numbered, generated when I installed a Ubuntu distribution on 
an external device dedicated to get the internal drive of another PC 
used at a place without Internet connection.

At the other place, grub stopped running when it got at line 62, because 
it did not find any 'hd1,msdos5' device, as device hd1 at installation 
time had got device hd0 at running time. So the only result of this line 
62 is to have had grub fail.

You can see on line 12 of the blkid listing that line 64 would have 
properly set root. You can also see that without lines 62 and 129, I 
would have been able to start the configuration and then run 
grub-mkconfig to adapt grub.cfg at the new configuration.

So here is the reason why I asked for discontinuing the generation of 
those "set root=" instructions whose only result is to have grub fail.

As long as I am concerned, I am quite able to suppress those lines by 
myself. The only real issue is to consider whether or not other people 
may act as I do and install a system in a place on a given configuration 
and used it at another place in another configuration.



Le 19/03/2013 07:50, Vladimir 'φ-coder/phcoder' Serbinenko a écrit :
> 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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grub.cfg.numbered
Description: Text document

blkid.numbered
Description: Text document