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The Restore-o-Mounter: The File Motel Revisited

Joe Moran and Bob Lyon
Legato Systems, Incorporated


We present a scheme for referencing and accessing saved (( footnote 1: We use the word "save" to denote the super set of "backup" and "archive"; save is also easier to conjugate than backup.)) files in a manner that is transparent to UNIX" applications. The scheme requires no kernel modifications. Instead, it uses a "mounted" process that allows users to change directories to the past and browse their saved files with their favorite utilities. The mounted process acts as a protocol gateway between NFS and a commercially available network backup product. Time travel is supported; users may change directories to any moment in the past. Any saved version (not just the most recent version) of any file can be viewed or recovered, even if the file has since been deleted.

Using this transparent method of retrieving saved files by naming their location in the past, a poor man's file migration scheme can be implemented by substituting a symbolic link to a saved location for a file. Once a file is referenced, the symbolic link can be replaced with its original file. This migration scheme requires no kernel modifications yet remains transparent to UNIX applications and users.

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