Files

Blake Ridgway 36d0c5b9d1 feat: add btrfs subvolume, snapshot, and rollback tooling

- init.sh: creates the @ / @home / @log / @snapshots subvolume layout
  on a target device (the installer step).
- snapshot.sh: scheduled read-only snapshots with pruning, installed as
  /usr/local/sbin/arcline-snapshot.
- rollback.sh: safe boot-to-snapshot rollback that refuses to touch the
  live @ and promotes a snapshot atomically.

2026-08-21 13:15:43 -05:00

1.7 KiB

Raw Blame History

btrfs in Arcline OS

Arcline OS is btrfs-native: the root filesystem layout is created at install time and snapshots are first-class, not bolted on.

Subvolume layout

Subvolume	Mount point	Purpose
`@`	`/`	system root — rolled back on failed upgrade
`@home`	`/home`	user data — not rolled back by default
`@log`	`/var/log`	logs survive rollbacks
`@snapshots`	`/.snapshots`	read-only snapshots live here

The layout is created by btrfs/init.sh <device> (this is what the installer runs). /etc/fstab templates live in each edition manifest and reference these subvolumes with subvol= mount options.

Tooling

btrfs/init.sh <device> — create the subvolume layout on a target device.
btrfs/snapshot.sh — snapshot / list / prune. Installed in images as /usr/local/sbin/arcline-snapshot and triggered automatically by the arcline-snapshot.timer systemd unit (see overlays/base/usr/lib/systemd/system/).
btrfs/rollback.sh — promote a snapshot back to @. Installed as /usr/local/sbin/arcline-rollback.

How a rollback works

Rollbacks are done from a rescue/live environment (never against the mounted @). The tool moves the current @ aside to @.rollback-<ts> and promotes the chosen snapshot to @. Because btrfs renames are atomic, a crash mid-way leaves a recoverable system on disk.

Compression

All subvolumes mount with compress=zstd:3 (see the edition fstab templates). Transparent compression is on by default.

1.7 KiB Raw Blame History