В Tue, 05 May 2015 18:54:03 +0200
Sebastian Pipping <sebast...@pipping.org> пишет:
> Hello!
>
>
> I noticed that GRUB stopped supporting installation to LVM volumes and
> that installing to loop devices also started failing unless --force is
> given. The Release of Debian jessie made me realize that GRUB
> 2.02~beta2 stopped doing what 1.99 did without complaining. So I did
> some debugging.
>
> A word on what this is needed for:
> I have a case where grub-install is asked to install to an LVM volume
> [1] that is later passed to Xen to boot a Xen guest. Inside the Xen
> guest the LVM volume is seen as a regular hard disk. So I can no longer
> use grml-debootstrap/grub-install to install to LVM volumes without
> patching at least one of those.
>
> To reproduce it:
>
> # touch /var/tmp/disk2
> # truncate --size=$((100*1024**2)) /var/tmp/disk2
> # loop_device_2="$(losetup --show -f /var/tmp/disk2)"
> # vgcreate vg "${loop_device_2}"
> # lvcreate --name lv -l 100%free vg
> # parted /dev/vg/lv mklabel msdos
> # parted /dev/vg/lv mkpart primary ext4 4m 100%
> # mkfs.ext4 /dev/mapper/vg-lvp1
> # mkdir /mnt/lv-root
> # mount /dev/mapper/vg-lvp1 /mnt/lv-root
> # mkdir /mnt/lv-root/boot
> # grub-install --boot-directory=/mnt/lv-root/boot /dev/mapper/vg-lv
> Installing for i386-pc platform.
> grub-install: error: disk
> `lvmid/GrSIBA-3EPT-TxGE-cnSa-glgA-pXpy-Kw8cOg/PD3WT8-956c-CEJ8-yPJE-ttGy-yACP-ffwTac'
> not found.
>
> When I add a device map containing that drive ..
>
> # echo -e
> '(lvmid/GrSIBA-3EPT-TxGE-cnSa-glgA-pXpy-Kw8cOg/PD3WT8-956c-CEJ8-yPJE-ttGy-yACP-ffwTac)\t/dev/mapper/vg-lv'
> > /mnt/lv-root/boot/grub/device.map
>
> .. grub-install replaces the "lvmid/*" drive to
> "hostdisk//dev/mapper/vg-lv" saying
>
> grub-install: warning: the drive name
> `lvmid/GrSIBA-3EPT-TxGE-cnSa-glgA-pXpy-Kw8cOg/PD3WT8-956c-CEJ8-yPJE-ttGy-yACP-ffwTac'
> in device.map is incorrect. Using hostdisk//dev/mapper/vg-lv instead.
> Please use the form [hfc]d[0-9]* (E.g. `hd0' or `cd').
>
> and remains complaining "disk `lvmid/...' not found.
> Since the docs at "13.1 How to specify devices" (docs/grub.info)
> advertise "lvmid/" in Git for valid drive syntax, that came unexpected
> to me.
> Inspecting the code of read_device_map shows that only
>
> (fd0) ...
> (hd0) ...
> (cd) ...
>
> of the documented syntax are actually registering the drive as-is (which
> does match the warning), everything else (including "(lvmid/*)") ends up
> being re-written to "(hostdisk/<file>)". So it does not allow me
> helping GRUB in finding the disk.
>
bor@opensuse:~/build/grub> cat boot/grub/device.map
(hd0) /dev/system/docker
bor@opensuse:~/build/grub> sudo pkgdatadir=$PWD ./grub-install -d grub-core
--boot-directory $PWD/boot --grub-mkdevicemap /tmp/device.map '(hd0)'
Installing for i386-pc platform.
Installation finished. No error reported.
Yes, device.map is *still* useful :)
>
> I did manage convincing grub-install to accept lvmid device map entries
> using the patch attached but I would also like to see something that
> works out of the box again (including loop devices), of course.
>
>
> Now that you know about the scenario and problem I would like to ask:
>
> * How you would like to see this addressed in GRUB code?
>
> * What replacements to "grub-install --boot-directory=<X> <Y>" can
> you think of for a temporary workaround?
> How would use existing GRUB commands to dump future MBR bytes needed
> to some regular file to apply that to any device using dd after or
> something like that?
>
>
> Many thanks in advance,
>
>
>
> Sebastian
>
>
> [1] from inside a tool called grmldeboostrap [2], a wrapper around
> deboostrap installing Debian to a given block device
> [2] https://github.com/grml/grml-debootstrap
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