Use of dump: verification technique, error recovery?

[B. Sam Blanchard]

Question:
	Can I induce a condition that will cause dump to restart a tape
	instead of aborting the whole dump?

	If so,
	is it too late to use the checkpoint at the end of tape #1 when
	dump is prepared to begin tape #2?
	(dump documentation mentions checkpoints)

	Alternatively,
	can I trick dump into writing 'some' tapes to /bin/null and others
	to /dev/rmt8 (thus allowing selective tapes to be written).  I think
	single user mode should insure that all data would match but am not
	sure if this is possible or if dump will complain about mix & match
	tapes.

I am doing backups on a VAX 11/785 running 4.3bsd UNIX using the program
backup.

The tapes are verified using:
	for the first tape only
		restore -tf /dev/rmt8 > /dev/null
	for all tapes
		dd if=/dev/rmt8 of=/dev/null bs=10k

	(looks familiar eh!)

The order of operations is:
	issue the dump command
	for each tape written
		allow dump to write to tape
		suspend dump (when it asks if next tape is mounted)
		verify tape appropriately
	done

By verifying each tape during the dump, I avoid having to redo tapes subsequent
to an error.

Situation:
	Today I got a hard error from my tape #2 (not bad with this sinerio).
	I aborted the dump and started over (rewritting tape #1 which had
	already been verified).

DUMP documentation:
	Dump documents itself as checkpointing after each tape so that dump
	itself can recover if dump finds an error in the current tape.

Question:
	Can I induce a condition that will cause dump to restart a tape
	instead of aborting the whole dump?

	Is it too late to use the checkpoint at the end of tape #1 when
	dump is prepared to begin tape #2?

	Alternatively,
	can I trick dump into writing 'some' tapes to /bin/null and others
	to /dev/rmt8 (thus allowing selective tapes to be written).  I think
	single user mode should insure that all data would match but am not
	sure if this is possible or if dump will complain about mix & match
	tapes.
-- 
B. Sam Blanchard         UUCP:  <backbones>!{iuvax,pur-ee}!bsu-cs!sam