On Fri, May 28, 2004 at 03:03:42PM -0400, Eric Siegerman wrote:
>....
>(Simply amdumping twice would not make *identical* copies, since
>the first run would change the files' last-access timestamps, if
>nothing else.)

Changing the last-access time of a file is only an issue for mechanisms
that open the files in question.  For example, tar opens (individual)
files that it reads.  On the other hand, {,ufs}dump does not:  the thing
it opens is a file system, so it does not change inode contents at all.

That said, there exist other reasons the product of another backup
process is unlikely to be an identical copy of the first.

IIRC, someone posted a note about how he ran an amdump, and as chunks
were written to the holding disk (well, before the chunks were taped &
unlinked), he made another link to each file, so after the first taping,
the files in the holding disk were still there, and an amflush run created
another tape with the same data.

Peace,
david
-- 
David H. Wolfskill                                 david AT egation DOT com