Internals - pdumpfs pdumpfs: a daily backup system similar to Plan9's dumpfs pdumpfs is a simple daily backup system similar to Plan9's dumpfs which preserves every daily snapshot. pdumpfs is written in Ruby. You can access the past snapshots at any time for retrieving a certain day's file. developed by Satoru Takabayashi % pdumpfs debian /archive debian -> /archive/YYYY/MM/DD/debian If file has not been changed, it doesn't copy the file, but just hardlinks. No special tools are required to access the past snapshots.