GNU-tar vs dump(1)

[Robert Elz]

> >One thing that worries me about using tar for dumps is that it updates
> >the access time of all the files that it reads.  Is there any way to
> >avoid this?
> 
> Not without changing "tar" to do an "fstat" before it starts reading ...
> and a "utime(s)" call to set the accessed time ...

Of course, doing this modifies the ctime field, which means that this
file (every file) is going to be dumped on your next incremental (unless
you're basing that on mtime, in which case your incrementals aren't
saving changed modes, owners, etc).

One of the very worst USG (sys III, PWB, whetever) "features" has been the
attempt to convince the world that a tape interchange format (cpio, tar,
whatever) is useable for dumps.  Its simply not true.  Backups are an
entirely different problem, and need an entirely different solution.

kre