copytape on sgi?

[Yates, John H.]

I have copytape working on a sun and Convex, but it fails on sgi.

 mt -t /dev/rmt/xmt0d0.1600 rewind
 copytape /dev/rmt/xmt0d0.1600 tape.tmp

gives:

 copytape: can't read input: Invalid argument

Anybody have this gem (or equivalent) working on an sgi? Thanks, John
yates at c.chem.upenn.edu

For those who don't know about copytape, from the manpage:
copytape duplicates magtapes.  It is intended for duplication of
bootable or other non-file-structured (non-tar-structured)
magtapes on systems with only one tape drive.
copytape is blissfully ignorant of tape formats.  It merely makes
a bit-for-bit copy of its input.
In normal use, copytape would be run twice.  First, a boot tape is
copied to an intermediate disk file.  The file is in a special format that
preserves the record boundaries and tape marks.  On the second
run, copytape reads this file and generates a new tape.
        % copytape /dev/rmt8 tape.tmp
        % copytape tape.tmp /dev/rmt8
        % rm tape.tmp
AUTHOR
David S. Hayes, Site Manager, US Army Artificial Intelligence Center.
Originally developed September 1984 at Rensselaer Polytechnic Institute,
Troy, New York.
Revised July 1986.  This software is in the public domain.