FW: How to read amanda tapes with standard unix/linux tools

Paul

The -overlooked- hyphen of dd was the culprit. 
I now get the desired response from the drive.
Thanks

Gerrit Hommersom


Hommersom, Gerrit (G) wrote:
> For emergency testing I want to read the amanda files with standard 
> Unix/Linux tools
> 
> W Curtiss preson's book suggests that amanda tapes can be read with 
> the command dd -if=/dev/nst0 bs=32k count=1

Note that dd does not take options with a hyphen, at not on any OS that I have 
access to.



> 
> Attempting to move it to the next file with
> mt /dev/nst0 fsf 1
> dd -if=/dev/nst0 bs=32k count=1
> persistingly returned the amanda header, nothinbg else

Which amanda header? There are two kinds: an amanda tapeheader and one 
amandaheader for each archivefile on tape.

> 
> This returns indeed the Amanda header but not the backup software used 
> (tar in my case)

Show us the header...


> Forcing a  listing with dd -if=/dev/nst0 bs=32k skip=x | tar -t - 
> returned either not output or the message "not a tar file"

Was it compressed archive? If yes then you also need the "-z" flag. Also you 
need to skip exactly 1 block (the amanda archive header), not "x" blocks. Also 
reading from stdin is accomplished by the "-f -" combination. Without the "-f" 
tar takes the argument as the file to extract from the archive. (The 
amandaheader in each archive even contains the commandline!)

That said, it probably boils down to:

   mt -t /dev/st0 rewind
   mt -t /dev/nst0 fsf 1
   dd if=/dev/nst0 bs=32k count=1

This gives the amanda archive header of the first archive.  Take a look at the 
commandline that amanda suggests for you.

   mt -t /dev/st0 rewind
   mt -t /dev/nst0 fsf 1
   dd if=/dev/nst0 bs=32k skip=1 | gtar -ztvf -

now you get a listing (omit the -z flag if the archive was not compressed).



-- 
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
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