Backer is a visual front end to the rsync command. It allows the user to select multiple folders and back them up to multiple locations. It stores your backup settings for you so that all your backups can be run easily using a single button click. Backer also tracks and logs your backup history for you.
The rsync command is available by default on both Mac and Linux. It is a command line program that efficiently transfers and synchronizes files between a computer and an external hard drive and across networked computers by comparing the modification times and sizes of files. Backer provides a visual interface to the rsync allowing you to point, click, and remember your backup settings. More Info »
By default Backer starts with /home as the root for finding your folders to backup, and /media for external or network locations to store backups of those folders. On Mac these locations are /Users and /Volumes.
You can select multiple folders under your home folder on the left. To backup a folder click the "Add" button below your home folder tree on the left. You can select multiple storage locations on the right by again clicking an "Add" button under the location tree. When Backer runs the backup process it will duplicate all folders added on the left side in each of the folders on the right.
So, for example, if you have two external or network drives added as backup locations on the right, the backup will duplicate the same folders on two separate drives. This is useful in providing extra redundancy to protect your backups. If one of your backup drives fails you would still have a redundant good backup protecting your files.