grub2 fails to detect partitions if it was installed into file

[Sergey Naumov]

Hello.

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

Thanks in advance,
Sergey.