Autochanger/Backups on Unix

[gst at gnosys.svle.ma.us (Gary S. Trujillo)]

> Seems to me you could do an awful lot with the file's update date.  In fact,
> recording the date and time of each level dump, you could implement backup
> levels too.  This is no excuse.

This is how the UNIX "dump(8)" command has always worked.  It keeps a file
someplace ("/etc/dumpdates" on some systems, I think) that records the date/
time of each dump level done since the "epoch."  Subsequent dumps are based
on the next lower level.  Thus if one does a level zero ("epoch") dump, the
file is reset to contain only the timestamp of that dump.  If you then do a
level 1 dump on the next day, only those files that have been created or
modified since level zero will be dumped, and so on.  One can use the tower-
of-hanoi algorithm to produce over time a set of dump tapes that go back a
long ways, plus others from more recent periods, which is handy once in a
while when one discovers having lost or messed up a file and knows it used
to exist or have a better state than more recent versions.
--
    Gary S. Trujillo                            gst at gnosys.svle.ma.us
Somerville, Massachusetts                {wjh12,bu.edu,spdcc,cdp}!gnosys!gst