Multiple cpio/tar files on Apple Tape

[Doug Tody X217]

>From article <AUXPOST%90032510412694 at PUCC.BITNET>, by MATLEVAN at EKU.BITNET (Jerry LeVan):
> Hello,
> Has anyone out there used the Apple Tape Cartridge to store
> multiple tar/cpio file archives? It is clear that the "norewind"
> device must be used, but does the tape driver write and eof mark?

Yes.  All unix tape drivers automatically write an EOT (double tape mark)
when a file opened for writing is subsequently closed.  If closed no-rewind,
the tape is left positioned between the file marks and the next file will
overwrite the second tape mark, giving you an EOF between the files (those
are the standard semantics, the details of what actually goes on at the
physical level with the Apple tape may differ, but I doubt that it matters).

> Should the "mt" command be used to write eof marks after each
> archive?

No.  That would probably give you an EOT, making the tape difficult to
read...  Just tar to the new-rewind device, and tar again for each
successive file.  Very easy.

> Is there any way to determine how many archives are stored
> on the tape...

It is not hard to write a program to count files and records on a tape,
but I don't know of anything in A/UX or standard unix.
-- 
Doug Tody, National Optical Astronomy Observatories, Tucson AZ, 602-325-9217
UUCP: {arizona,decvax,ncar}!noao!tody  or  uunet!noao.edu!tody 
Internet: tody at noao.edu             SPAN/HEPNET: NOAO::TODY (NOAO=5355)