What's the easiest way to do a backup and verify?

[Loren M. Lang]

On Mon, Mar 07, 2005 at 09:47:31AM -0500, Jerry McAllister wrote:
> > 
> > Is there an easy way to combine a backup and verify when doing backups
> > with dump?
> > 
> > On Windows NT it's just a matter of checking a box.  I seem to recall
> > the last time I looked into this on UNIX there was no easy way to
> > accomplish a verify operation for a backup, but perhaps things have
> > changed with FreeBSD 5.3 (?).
> > 
> > I've never had a problem with backup (I backup to DAT tape), but I'd
> > feel better if every backup was followed by a verify to make sure the
> > tape is readable.
> 
> Actually, if used frequently for backups - such as every day, DAT is
> notoriously prone to failure.    So, it is a good idea to check dumps
> made to DAT.   Unfortunately, there is not a reasonable way to 
> automatically do it.   There is a verify, but it cannot work on a
> running system, because it compares files (inodes) on the tape back
> to the ones on disk.  Any changes mean an error, even if it was a
> real change in the file between the time it was written and the
> time it was read back.
> 
> The only real thing you can do is to read back the tape and look
> for a couple of files with fairly high inode numbers for each file
> system dumped.    If you can read them, you can assume the tape
> is readable.

I'm not very familiar with tapes, but I think that the dump is written
straight out to something like /dev/st0 right?  So then wouldn't a
second dump of the same snapshot diffed to the tape device be a good for
a verify?

Position tape at beginning of dump
dump / | diff - /dev/st0

Though I don't have much experience with either dump or tapes to verify.

> 
> ////jerry
> 
> > 
> > -- 
> > Anthony
> > 
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