Installation of EFI on seperate disk than /boot

This document (000019849) is provided subject to the disclaimer at the end of this document.

Environment

SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Server 12

Situation

During installation, the EFI boot partition was installed on on different disk than the disk on which /boot is located. For example:

NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda             253:0    0   20G  0 disk 
└─vda1          253:1    0  500M  0 part /boot/efi
vdb             253:16   0   20G  0 disk 
└─vdb1          253:17   0 19.5G  0 part 
  ├─system-swap 254:0    0  1.1G  0 lvm  [SWAP]
  ├─system-root 254:1    0 12.8G  0 lvm  /
  └─system-home 254:2    0  5.6G  0 lvm  /home

With above configuration, unattended system boot will fail and fall back into grub shell:

If the boot process was interrupted and select manually the "sles-secureboot" from KVM Boot Manager, then the system will boot fine.

Resolution

Looking at above grub> prompt screenshot, grub was able to detect only the first hard-disk, it was not able to identify the disc on which /boot is located to read grub.cfg from. Then most likely the reason behind this is because the KVM host was set to boot only from 1st HDD. Adding the 2nd HDD to boot pool should fix the problem like below:

On other systems where the above is not possible, having /boot and /boot/efi on the same disk is a way to overcome the issue, such as:

NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda             253:0    0   20G  0 disk 
├─vda1          253:1    0  500M  0 part /boot/efi
└─vda2          253:2    0  500M  0 part /boot

Cause

grub enters grub emergency shell because it is not able to read grub.cfg file if that is located on another disk.

Additional Information

It is strongly recommended to keep the efi boot partition on the same disk with /boot and root filesystem.

Disclaimer

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