Re: grub2 fails to detect partitions if it was installed into file

[Sergey Naumov]

Thanks, Pascal, that helped a bit.

But now there is another problem:
error: attempt to read or write outside of partition.

So grub see partition and its content, it can even load some modules from
(hd0,msdos1)/boot/grub/i386-pc.

But when I'm trying to load some other modules, like "normal", I see this
error:
grub rescue> ls
(hd0) (hd0,msdos2) (hd0,msdos1)
grub rescue> ls (hd0,msdos1)/boot/grub
./ ../ gfxblacklist.txt unicode.pf2 i386-pc/ locale/ fonts/ grubenv grub.cfg
grub rescue> set root=(hd0,msdos1)
grub rescue> set prefix=(hd0,msdos1)/boot/grub
grub rescue> insmod normal
error: attempt to read or write outside of partition.

What is also interesting, if I use --modules=part_msdos,ext2 instead of
--modules=part_msdos, then grub tries to load a system, but neither
succeeds nor emits rescue shell - it just hangs.

As to your question - I used "losetup -o 1M -f image.img" to create loop
device that I can format with mkfs.ext4.

Thanks,
Sergey.


2018-07-17 21:12 GMT+03:00 Pascal Hambourg <address@hidden>:

> Hello,
>
> Le 17/07/2018 à 18:09, Sergey Naumov a écrit :
>
>>
>> I'm trying to prepare an image that I can dd into disk or boot using PXE,
>> so I install basic system + kernel + grub-pc into directory, then create
>> an
>> image file, partition it using sfdisk, mount main partiton (ext4), copy
>> content of the rootfs into it, and then run grub-install and update-grub
>> under chroot.
>>
>> Everything seems OK, grub.cfg detected kernel and initramfs installed into
>> created image, but when I try to boot this image either on real system or
>> using kvm, grub2 can't find device partitions. What could be a reason of
>> it?
>>
>> I posted the question with more detailed explanation here:
>> https://serverfault.com/questions/922319/grub2-fails-to-
>> detect-partitions-if-it-was-installed-into-file
>>
>
> You really could have copied all the relevant information in your post to
> the list, so subscribers do not have to fetch them on the web.
>
> How did you make the ext4 partition in the image appear as a block device
> so that it can be mounted ?
>
> AFAIK, GRUB looking for the filesystem containing /boot/grub by UUID means
> that grub-install believes that it is on a different drive from the
> boot+core image. So maybe grub-install did not care to embed the MSDOS
> partition table driver into the core image. You can try to force it with
>
> grub-install --modules=part_msdos <other parameters>
>