On Sat, Oct 09, 2004 at 03:07:48PM +0100, Gaby Vanhegan wrote:
> I'm using Amanda to backup a number of machines on our network and I 
> keep getting this error in the mail report:
> 
> >FAILED AND STRANGE DUMP DETAILS:
> >
> >/-- ltsn19-ws. /logs/apache lev 1 STRANGE
[snip]
> >? gtar: ./prs-referrer_log: file changed as we read it
> >? gtar: ./prs-transfer_log: file changed as we read it
[snip]
> >
> Presumably because the website is getting traffic whilst Amanda is 
> dumping that folder.  gtar is complaining a file that has been modified 
> whilst it has packed it, but it seems to archive the file OK.  

Indeed, that is the usual reason, however bear in mind that depending
upon *how* the file changed, the fact that gtar put it in the archive
does not mean that the copy in the archive isn't corrupted.  That's
the reason for the warning. 

> Is there a dumptype I can use that will stop these errors happening?

The only way to prevent errors like that are to ensure that
nothing you're backing up can change while the backup is running.

In the general case that means either:
        a.) Unmount the filesystem before the backup and keep it that way
                until the backup is done (requires DUMP rathar then TAR).
        b.) If your platform supports it, use filesytem snapshots
                and backup the snapshot rather than the live filesystem.
        c.) Live with the occasional error, and if nessecary take steps
                to ensure that the same file won't be changing during
                the following Amanda run so you'll have at least one
                consistant copy on tape.

In this specific case, you could arrange for Apache to rotate its
logs just prior to the start of the Amanda run.  In your dumptype
you'd then exclude the active log files.