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

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 withmt /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).



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Paul Bijnens, Xplanation                            Tel  +32 16 397.511
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