btrfs_snapshot_rotate

Take btrfs snapshots and rotate them out based on a retention policy.

This is a lightweight alternative to tools like snapper. It was built with a simple use case in mind: run the script with a daily cron job, and let the script evaluate what needs to be done.

Install

Copy the btrfs_snapshot_rotate.rb file to your preferred location. You will need ruby to run it. You can either do this by calling ruby /your/path/to/btrfs_snapshot_rotate.rb or make it executable chmod +x /your/path/to/btrfs_snapshot_rotate.rb and execute it directly.

Script requires ruby gem 'colorize', install with:

gem install colorize

Configure

There are a few configuration lines you should edit. Use your favorite text editor to open and edit btrfs_snapshot_rotate.rb.

BtrfsCommand = '/usr/sbin/btrfs'
SnapshotConfigurations = [
	{
		full_paths_to_mount: ['/mnt/btrfs-store-root'],
		full_path_of_source_subvolume: '/mnt/btrfs-store-root/store',
		full_path_of_snapshot_directory: '/mnt/btrfs-store-root',
		snapshot_filename_prefix: 'store-snapshot',
		keep: { days: 14, weeks: 10, day_of_week: "Monday", months: 12, years: 5 }
	}
]

1. BtrfsCommand: this is where the btrfs executable is installed on your system. If you don't know, type which btrfs and copy the result
2. SnapshotConfigurations: this contains one or more sets of attributes about your snapshots

• full_paths_to_mount: if any path isn't normally mounted, you can note the path(s) and it will be mounted before started and dismounted after. An empty array [] will skip all mount/umount operations
• full_path_of_source_subvolume: the subvolume you want to snapshot
• full_path_of_snapshot_directory: where you store your snapshots
• snapshot_filename_prefix: this string will be the filename prefix. A value of 'mysnapshot' will result in files that looks like 'mysnapshot-YYYY-MM-DD' (where YYYY-MM-DD is the date of the snapshot).
• keep: number of days, weeks, months, and years of snapshots to keep. For weeks, you need to specify a day of the week to keep, e.g., "Monday"

You can add as many snapshot configurations as you'd like, for example, to snapshot two separate subvolumes:

BtrfsCommand = '/usr/sbin/btrfs'
SnapshotConfigurations = [
	{
		full_paths_to_mount: ['/mnt/btrfs-store-root'],
		full_path_of_source_subvolume: '/mnt/btrfs-store-root/store',
		full_path_of_snapshot_directory: '/mnt/btrfs-store-root',
		snapshot_filename_prefix: 'store-snapshot',
		keep: { days: 14, weeks: 10, day_of_week: "Monday", months: 12, years: 5 }
	},
	{
		full_paths_to_mount: [],
		full_path_of_source_subvolume: '/',
		full_path_of_snapshot_directory: '/.root-snapshots',
		snapshot_filename_prefix: 'root-snapshot',
		keep: { days: 7, weeks: 8, day_of_week: "Monday", months: 4, years: 0 }
	}
]

Cron

This is an example cron setup to have the root user run the script nightly at 2am:

crontab -e

And add the following line:

0 2 * * * ruby /root/btrfs_snapshot_rotate.rb -y > /dev/null 2>&1