A file system that will allow a limited form of undoing destructive operations. Unix users often remove files unintentionally.10 Files that get removed will first be copied over to the backup storage (using Statefs). These files can get expired (perhaps via Expirefs ) after a period of disuse. But in the short term, a user realizing the unintentional loss of his/her files could simply copy them from the undo file system back to their original location.
It is important that Undofs will not allow non-root users to delete files from the backup location, so that they could not be inadvertently removed.