[CLUE-Tech] tar to tape with compression

[Dave Hahn]

A few other things:

1 - Make sure your gzip is 1.3 or that you have patched against the 2GB
barrier.  Also, I've found other odd problems with gzip pre 1.3
2 - Use bzip2 instead of gzip - about 15%-20% better compression
3 - Declare the tape size and blocks in the tar command.  Seems to make
tar happier overall.

my $.02

-d
 

On Wed, 2002-11-20 at 22:51, Jeffery Cann wrote:
> 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
> -- 
>     planet earth (tm)
> http://jefferycann.com/
> _______________________________________________
> CLUE-Tech mailing list
> CLUE-Tech at clue.denver.co.us
> http://clue.denver.co.us/mailman/listinfo/clue-tech