Bup – towards the perfect backup
A shoutout for attic https://attic-backup.org/Attic is one of the new-generation hash-backup tools (like obnam, zbackup, Vembu Hive etc). It provides encrypted incremental-forever (unlike duplicity, duplicati, rsnapshot, rdiff-backup, Ahsay etc) with no server-side processing and a convenient CLI interface, and it does let you prune old backups.All other common tools seem to fail on one of the following points- Incremental forever (bandwidth is expensive in a lot of countries)- Untrusted remote storage (so i can hook it up to a dodgy lowendbox VPS)- Optional: No server-side processing needed (so i can hook it up to S3 or Dropbox)If your backup model is based on the old' original + diff(original, v1) + diff(v1, v2).. then you're going to have a slow time restoring. rdiff-backup gets this right by reversing the incremental chain. However, as soon as you need to consolidate incremental images, you lose the possibility of encrypting the data (since encrypt(diff()) is useless from a diff perspective).But with a hash-based backup system? All restore points take constant time to restore.Duplicity, Duplicati 1.x, and Ahsay 5 don't support incremental-forever. Ahsay 6 supports incremental-forever at the expense of requiring trust in the server (server-side decrypt to consolidate images). Duplicati 2 attempted to move to a hash-based system but they chose to use fixed block offsets rather than checksum-based offsets, so the incremental detection is inefficient after an insert point.IMO Attic gets everything right. There's patches for windows support on their github. I wrote a munin plugin for it.Disclaimer: I work in the SMB backup industry.