Re: Installing grub to raw image

[Jeremy Davis]

Hi Andrei,

Thanks for your guidance.

My primary issue appears to be a bug in the Jessie version of grub
(2.02~beta2-22). I installed 2.02~beta2-28 (from Stretch) and it all
seems to be working as it should...

Like you suggested it seems grub doesn't realise that
/dev/mapper/loop0p1 is the child of /dev/loop0 whereas the newer version
does.

Regards,
Jeremy

On 08/10/15 06:07, Andrei Borzenkov wrote:
> 07.10.2015 05:32, Jeremy Davis пишет:
>> Hi,
>>
>> I am trying to install grub to a raw image (i.e. a flat file that will
>> be used to house a VM). Host & guest image both Debian Jessie
>>
>> I have partitioned the file:
>> part 1 : ext2 (for boot)
>> part 2 : LVM (for root & swap)
>>
>> I have the raw mounted to /dev/loop0 with kpartx so these partitions
>> map to:
>>
>> part 1 : /dev/mapper/loop0p1
>> part 2 : /dev/mapper/loop0p2
>>
> 
> I can reproduce something similar using grub2 in openSUSE Tumbleweed
> (2.02~beta2 with selected patches). The problem is that grub fails to
> detect that /dev/mapper/loop0p1 is partition of /dev/loop0 and so it
> does not include partition driver. The UUID in my case was correct (that
> of the first partition), but grub simply could not access it.
> 
> Current upstream seems to work for me in this configuration. You may
> want to test if it works for you.
> 
>> The LVM setup (vg labelled "lv")on part 2 provides:
>> /dev/mapper/lv-root
>> /dev/mapper/lv-swap_1
>>
>> I then have it mounted like this:
>>
>> /dev/mapper/lv-root -> /mnt
>> /dev/mapper/loop0p1 -> /mnt/boot
>>
>> I then install grub like this:
>>
>> devicemap=/mnt/boot/grub/device.map
>> chroot /mnt grub-mkdevicemap
>> chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg
>> grub-install --force --grub-mkdevicemap=$devicemap --root-directory=/mnt
>> /dev/loop0
>>
> 
> --grub-mkdevicemap is a) no-op, it is accepted for legacy reasons only
> and b) you are using it incorrectly anyway, it pointed to a program to
> rebuild device.map, not to device.map itself.
> 
>> Which appears to install as it should:
>>
>> # chroot /mnt grub-mkdevicemap
>> # chroot /mnt grub-mkconfig -o /boot/grub/grub.cfg
>> Generating grub configuration file ...
>> Found linux image: /boot/vmlinuz-3.16.0-4-amd64
>> Found initrd image: /boot/initrd.img-3.16.0-4-amd64
>> done
>> # grub-install --force --grub-mkdevicemap=$devicemap
>> --root-directory=/mnt /dev/loop0
>> Installing for i386-pc platform.
>> Installation finished. No error reported.
>>
>> (note that both systems are 64 bit so maybe this is the issue? But i
>> doubt it as the host has the same info...)
>>
>> So this appears to all complete fine...
>>
>> But when I boot the raw image I get an error about a device not found (a
>> UUID that I have no idea where it comes from. It does not appear to
>> match any of the UUIDs that I see in the grub.cfg so I have no idea
>> where this is coming from!?)
>>
>> I can fix grub easy enough from the vm:
>> -boot with live iso
>> -mount /dev/mapper/lv-root as /mnt & /dev/sda1 as /mnt/boot
>> # grub-install --root-directory=/mnt /dev/sda
>>
>> Once grub is repaired than all works as it should, however I want it to
>> just work from the start...
>>
>>  From looking around inside the (unbootable) raw it just looks like grub
>> wasn't installed properly...
>>
>> # ls -l /mnt/grub
>> total 2363
>> -rw-r--r-- 1 root root      50 Oct  7 01:47 device.map
>> -r--r--r-- 1 root root    5657 Oct  7 01:47 grub.cfg
>> -rw-r--r-- 1 root root 2400500 Oct  6 10:18 unicode.pf2
>>
> 
> Yes, it looks like grub installed somewhere else. You may want to run
> grub-install --debug ... to see what it did.
> 
>> Nothing like (working) /boot/grub on the host:
>>
>> # ls -l /boot/grub
>> total 2380
>> drwxr-xr-x 2 root root    4096 Aug 31 01:01 fonts
>> -r--r--r-- 1 root root    7882 Oct  7 00:52 grub.cfg
>> -rw-r--r-- 1 root root    1024 Aug 31 01:01 grubenv
>> drwxr-xr-x 2 root root   12288 Oct  7 00:56 i386-pc
>> drwxr-xr-x 2 root root    4096 Aug 31 01:01 locale
>> -rw-r--r-- 1 root root 2400500 Aug 13 13:08 unicode.pf2
>>
>> FWIW the fixed /boot/grub dir looks the same as the host...
>>
>> Any help/guidance/insight/etc warmly welcomed!
>>
>> Regards,
>> Jeremy Davis
>>
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