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