I've been using BackInTime (https://wiki.ubuntuusers.de/Back_In_Time/) since 6 years and happy with it. - it's using rsync and hardlinks, the files on the backupdrive are just normal files - it got "smart delete" of old backups (e.g. keep 1 backup per year older 1 year, 1 per month older 1 month and 1 per week older 1 week) - starts an backup automatic in background if you attach the external drive (with udev, if you want it) - has a nice simple ui (i like it)