composefs-native/boot: Handle systemd-boot and grub

[Johan-Liebert1]

Fix Grub boot error caused by #1541. Introduce a --bootloader cli option to --composefs-native. Depending upon the type of bootloader passed in we write BLS configs respectively

[gemini-code-assist]

Code Review

This pull request introduces support for both systemd-boot and grub by adding a --bootloader option, which is a great enhancement. The changes are well-structured, particularly the use of the BLSEntryPath struct to handle bootloader-specific paths. I've identified a critical issue with temporary directory handling that could lead to resource leaks, and a high-severity issue regarding backward compatibility for existing deployments. Addressing these will make the implementation more robust.

[cgwalters]

LGTM as is however...I still think we should detect grub instead via looking for its config files

[Johan-Liebert1]

I still think we should detect grub instead via looking for its config files

Is there some peculiar reason why we should be looking for grub config files? I think the EFI vars approach is a bit better as it also lets us distinguish BIOS/UEFI

[cgwalters]

Is there some peculiar reason why we should be looking for grub config files? I think the EFI vars approach is a bit better as it also lets us distinguish BIOS/UEFI

In theory we should work with any bootloader that implements the spec instead of specifically detecting systemd-boot - right?

[Johan-Liebert1]

Right. AFAIK bootloaders on UEFI will populate the LoaderInfo file with the bootloader name, which we check right now. Though, we do default to Grub if we can't find /sys/firmware/efi/efivars, in which case it does become necessary to look for bootlaoder specific config files.