Historically, dump was *always* used on unmounted filesystems.  Tools like
AMANDA break that expectation.  Backing up a live filesystem sometimes causes
problems for tools like dump, depending on what is changing while the backup
runs.  If you see errors during a dump of a mounted filesystem, try again with
the filesystem unmounted, and see if that fixes the problem.

In theory, the page cache changes in the 2.4 Linux kernel can cause problems
to happen more frequently than in prior versions.  Caveat emptor.

--

If you want to dump on remote tapes as a non-root user, you will need to make 
the dump executable setuid root, so that it can allocate a privileged port 
for the outgoing network connection.  This is not the default, since it is
not commonly needed, and setuid executables are targets for security attacks.

