btrBackup

A "simple" tcl script for local backups (e.g. to external harddrives) when source and target filesystem are both btrfs filesystems.

Requirements

You need

• tcl
• rsync
• btrfs-progs

Installation

Copy btrbackup.tcl into a directory in your PATH, e.g. /usr/bin, and btrbackupconfig.tcl into /etc. If you want logrotation, put the logrotate file to /etc/logrotate.d/btrbackup or wherever your distro stores logrotate configuration.

Backup Preparations

You need to setup mountpoints for the root subvolume in your fstab for both source and target filesystem. The mountpoints need to be "noauto" in fstab - they are mounted during backup. You need to create subvolumes on your target filesystem to sync your files to. For each target subvolume you need to create a directory for storing snapshots of it.

The example configuration assumes the following setup:

A btrfs partition with subvolumes "root-subvol", "var-subvol" and "boot-subvol" for "/", "/var" and "/boot" and mountpoint "/mnt/root-filesystem" in fstab. A btrfs partition with a subvolume "home-subvol" for "/home" and mountpoint "/mnt/home-filesystem" in fstab.

An external harddrive with subvolumes "backup-root" and "backup-home" and mountpoint "/mnt/backup". The filesystem contains two directories (or subvolumes) "snapshots-root" and "snapshots-home".

So fstab might contain something like:

# system
LABEL=ssd-btr    /                    btrfs    subvol=root-subvol,compress=lzo   0 0
LABEL=ssd-btr    /boot                btrfs    subvol=boot-subvol                0 0
LABEL=ssd-btr    /var                 btrfs    subvol=var-subvol                 0 0
LABEL=hd-btr     /home                btrfs    subvol=home-subvol                0 0

# backup
LABEL=ssd-btr    /mnt/root-filesystem btrfs    noauto                            0 0
LABEL=hd-btr     /mnt/home-filesystem btrfs    noauto                            0 0
LABEL=backup-hd  /mnt/backup          btrfs    noauto                            0 0

Configuration

An example configuration is given in btrbackupconfig.tcl which is assumed to reside in "/etc". You have one section with expire-rules (inpsired by the backup-tool dirvish). There you specify rules for the backup target snapshot to keep. Other snapshots will be deleted at the beginning of a backup run.

In the example configuration only the most current versions of the root-snapshots are kept. Snapshots of the "/home"-backup have a somewhat more complex keeping-ruleset:

• Keep the first one of every year.
• Keep the first one of every of the last 12 months.
• Keep everything of the last 30 days.
• Keep the last 3 snapshots.

Then comes the backup setup. You can setup multiple backup targets. For each target you need to specify its mountpoint and its target subvolumes with snapshot-directory and expire ruleset.

Then you specify syncrules containing a source mountpoint, a source subvolume, the target subvolume with a relative path and directories to exclude for rsync (they will be extended by "/**".

Each target setup has a name by which it can be run later.

Running Backups

With the example configuration and setup you could simply run:

$ btrbackup.tcl my_backup

Logs will be printed, extended logs including rsync information are kept in

/var/log/btrbackup.log