1. Make sure a newer kernel is loaded from mainline: I'm using 2.6.33 @ the moment.
2. sudo apt-get install btrfs-tools
3. Attach the backup drive & partition as needed using fdisk.
4. mkfs.btrfs (new partition)
5. Create a directory to mount to, such as /media/backup
6. Edit /etc/modules to add btrfs
7. Edit /etc/fstab with the following modified for your needs...
(new partition) /media/backup btrfs compress 0 0
8. Update your boot files with update-initramfs -u
9. Make a backup script to run daily: example /etc/backup.sh
rsync -avlh (folder to backup) /media/backup/(folder to backup)
btrfsctl -s /media/backup/$DATE /media/backup
9. Add the script to your /etc/crontab file (and maybe run /etc/init.d/cron restart afterwards)
30 20 * * * root sh /etc/backup.sh
* Btrfs Wiki
* "Back up like an expert with rsync"
* Blogger's entry on getting btrfs to work with Debian/Ubuntu