Boot methods and snapshots

Boot method	Firmware	Recommended ESP	Bootable Btrfs snapshots	Recommended for
GRUB	UEFI and legacy BIOS	300 MiB	Yes	Compatibility, dual boot and legacy BIOS
Limine	UEFI + GPT	2 GiB	Yes	Modern, explicit boot configuration
systemd-boot	UEFI + GPT	2 GiB	Yes	Compact UEFI boot management
UKI	UEFI + GPT	2 GiB	No current boot-snapshot integration	Advanced UKI users
EFI Stub	UEFI + GPT	2 GiB	No current boot-snapshot integration	Direct firmware boot users

Choose GRUB when uncertain. CatOS manages Limine with limine-tool, systemd-boot with kernel-install, and UKI with systemd tooling.

Snapshot combinations

Bootable snapshots require a Btrfs root filesystem and a supported boot method:

GRUB         + Btrfs → Snapper + grub-btrfs
Limine       + Btrfs → Snapper + limine-btrfs
systemd-boot + Btrfs → Snapper + sdboot-btrfs
UKI          + Btrfs → no automatic snapshot setup; configure Snapper manually
EFI Stub     + Btrfs → no automatic snapshot setup; configure Snapper manually

Automatic snapshot policy

catos-snapper-config creates a single pre-transaction snapshot when:

• a transaction changes kernel, initramfs, firmware, DKMS, UKI, encryption or other boot-critical paths; or
• at least 25 distinct packages are changed in one transaction.

It records the reason and package count, enables number-based cleanup and does not enable hourly snapshots by default.

Booting versus rolling back

Booting a snapshot lets you test an earlier system state. A permanent rollback is a separate explicit operation. Snapshots normally share the same disk as the live system and do not replace independent backups.

After installation, check:

findmnt /
snapper list
systemctl status snapper-cleanup.timer