[CLUE-Tech] tar to tape with compression

[Jeffery Cann]

Greetings.

My tape drive holds 5 GB compressed data.  To this point, I have not run out 
of room on the tape during nightly backups.  I use 'tar cvfP ... ' to do the 
backup (... is the list of files to save).  I use 'tar dvf /dev/st0' to 
validate the archive.

Lately, I think I started using all of the space on the tape because I see the 
following in my backup log (which is the stdout of the tar command):

   tar: /dev/st0: Warning: Cannot close: Input/output error

So, I thought I should tell tar to use compression.  I tried it on my /etc 
directory:

$ tar zcvfP /dev/st0 /etc

This works, but the corresponding validation command:

$ tar zdvf /dev/st0

produces this output:

	...
	/etc/shadow.bak
	/etc/group.bak

	gzip: stdin: decompression OK, trailing garbage ignored
	/etc/mime.types
	/etc/mailcap
	/etc/gshadow.lock
	/etc/group.lock
	tar: Child returned status 2
	tar: Error exit delayed from previous errors

I understand this to mean that tar (by way of gzip?) is padding the archive to 
make an even block size for the tape.  I assume that this is message is 
innocuous for my purpose of validating the archive.  Is this a correct 
assumption?

TIA
Jeff
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