I have a NAS that runs NAS4Free. It has two hard drives (formatted as UFS), which run separately (so no RAID/JBOD).
On one hard drive, I want to backup my audio and video files, and on the other hard drive all my other files (text files, PDFs, images, etc.).
The files that have to be backed up all come from a single computer, running GNU/Linux. For this computer, I’m looking for a backup software (must be FLOSS) that, after configuration, automatically sends the files to my NAS (to the correct hard drive, depending on my initial configuration which folders should go to which drive).
My NAS does not necessarily run 24/7, so the backup software should be able to handle this. Being able to pause/cancel a current backup process would be useful.
Only files that were changed should be transferred (and ideally only the changes, not the whole files). Note that even my binary files might be changed, e.g., when tagging music.
On the NAS, I want to be able to access previous versions of the files, and ideally each backup on the NAS (e.g., in date-based folders) would consist of all files, by making use of hard links. So for (manually) backing up my backup, I could copy a specific date folder from the NAS to an external drive, and then have all my files (as from that date).
If I need to restore something, I’d like to be able to retrieve it manually (e.g., by SSH-ing into the NAS), so that I’m not bound to using this backup software. However, the backup software might also offer a more convenient way to access (or even rollback) files, as long as it’s optional.
I won’t use encryption (storage as well as transfer can be unencrypted).