Actually one common mistake is to use –files-from to supply restic with a list of possible changed files (determined by some external tool or scripting etc..) instead of just giving a path (and maybe excludes) and letting restic do the change detection. This has basically two consequences or misunderstandings:
- restic uses in this case a different path list for each backup which prevents restic from using a parent snapshot. IF this list really only contains changed files, using no parent is ok, but if you do have unchanged files, this is typically even slower than just using a single path and letting restic do the change detection.
- Some people think that providing such a list is necessary to do an incremental backup and thus saves space in repository. This is however not true - check out, how the deduplication works in restic. Moreover providing such a list in fact removes information and makes restores much more difficult: You cannot distinguish anymore between files being removed from the list because they have not changed and files being removed from the list because they have been removed from the filesystem. I.e. you do not have a snapshot of the disc’s state anymore and therefore have trouble toe restore such a state - and this is exactly what a backup tool should be for…
TL;DR: Using –files-from is in most cases not necessary, but can be a source of mistakes or misunderstandings!