Bug#1004514: grub-common: background images don't work with luks encrypted lvm root partition

[khimaros]

Package: grub-common
Version: 2.04-20
Severity: important
Tags: upstream

the core issue is that grub-probe is not reporting cryptodisk abstraction when the block device below the lvm is luks encrypted.

/usr/share/grub/grub-mkconfig_lib relies on this output to decide whether to create the background cache on the /boot partition. because cryptodisk is not returned as an abstraction, the cache is never created and cannot be displayed at boot time.

this is the output of grub-probe:

# grub-probe -t abstraction /usr/share/images/desktop-base/desktop-grub.png
lvm

however, the file is definitely on an encrypted lvm volume:

# stat --printf="%m\n" /usr/share/images/desktop-base/desktop-grub.png
/

# lsblk
NAME                 MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINTS
nvme0n1              259:0    0 476.9G  0 disk 
...
└─nvme0n1p3          259:3    0 476.7G  0 part  
  └─nvme0n1p3_crypt  253:0    0 476.7G  0 crypt 
    └─fnord--vg-root 253:1    0 476.7G  0 lvm   /

# mount -vf /
mount: /dev/mapper/fnord--vg-root mounted on /.

# pvdisplay
PV Name /dev/mapper/nvme0n1p3_crypt
VG Name fnord-vg
...

# cryptsetup status nvme0n1p3_crypt
/dev/mapper/nvme0n1p3_crypt is active and in use.
  type:     LUKS2
  device:   /dev/nvme0n1p3
...