Cannot boot after installing onto secondary disk

[mchf]

Scenario

1. Running d-installer in a TW virtual machine. Available disks sda, sdb. System running from sda, sdb empty (even non-partitioned)
2. d-installer used to install TW product onto /dev/sdb
3. installation came to the end with no problem, asking for reboot
4. Turned VM with d-installer off, attached disk image of sdb to another machine to boot installed system
5. installed system didn't boot, crashed into grub rescue
   

Details from debugging

• I was able to start normal mode manually from grub rescue using

grub rescue> set prefix=(hd0,gpt2)/@/boot/grub2
grub rescue> set root=(hd0,gpt2)
grub rescue> insmod normal
grub rescue> normal

• however (hd0,gpt2)/@/boot contains only grub2 folder but no kernel and so on. See
  

[mchf]

The issue is caused by using the d-installer for unsupported use case.

Core of the issue is caused by the fact that installation is targeted against second disk /dev/sdb in grub's word (hd1). So, when the sdb disk image is later detached and inserted into another machine it changes its relative name to /dev/sda resp (hd0) and grub gets confused.

Here is how you can boot the target from grub rescue:

grub2 rescue> set root=(hd0,gpt2)
grub2 rescue> set prefix=(hd0,gpt2)/@/boot/grub2
grub2 rescue> insmod normal
grub2 rescue> normal
grub2> insmod btrfs
grub2> linux /@/.snapshots/1/snapshot/boot/vmlinuz root=/dev/sda2
grub2> initrd /@/.snapshots/1/snapshot/boot/initrd
grub2> boot

to make it permanent run as root:

# grub2-install /dev/sda
# grub2-mkconfig -o /boot/grub2/grub.cfg

[mchf]

As I tried to explain, d-installer "works as expected" here. For those who really wants / needs to use the d-installer in a way as described in the description there is a workaround mentioned above.

I've nothing more to add, so closing.

[imobachgs]

Very useful information. Thanks a lot, @mchf. I will move this tip to the project's wiki.

[imobachgs]

Summarized here. Thanks!