[Gllug] Slurp an entire tape to file with dd

[Mark Williams]

> Hello,
>
> We're having a *lot* of fun trying to restore some backup tapes made
> with Veritas 8.6. The rant potential is considerable...
>
> I would like to transfer the entire 40GB of tape to a file, and so tried
> this in Knoppix:
>
> dd if=/dev/nst0 of=/mnt/myusbdisk bs=128k
>
> But dd will stop (without any error) and although repeating the command
> will read another chunk of unpredictable length, I'm worried bits are
> getting missed out and simply splicing the chunks together won't work.
>
> Since dd doesn't report any I/O error I'm assuming its coming across
> EOF.
>
> Is there any way I can say "do your absolute damnedness to read 327680
> blocks of 128k from this device"?
>
> Thanks in advance,
> TomSW

Hi Tom,

I have successfully used dd to clone a (small) hard disk partition to a 
file. The EOFs in the individual files on the partion were not a problem 
because the partition itself is a block device. I think the reason you are 
having problems with EOFs is because /dev/nst0 is a character device. I 
don't know much about tapes & their associated devices, but perhaps there is 
something else in /dev that you could use to access your tape as a block 
device instead.

Also, I'm wondering if, once you've solved the EOF problem, you might have a 
problem with large file support. Depending on your kernel & libc, you may or 
may not be able to create files >2GB.

Hope this helps,

Mark 


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