How to get past end of cpio archive on tape

[Daniel A. Graifer]

In article <1023 at mwtech.UUCP> martin at mwtech.UUCP (Martin Weitzel) writes:
%In article <301 at bria.AIX> mike at bria.AIX (Mike Stefanik/78125) writes:
%:First you have to skip over the first "part" of the tape that you cpio'd to;
%:use the no-rewind tape device (ours is rmt4) and do:
%:
%:	$ dd if=/dev/rmt4 of=/dev/null bs=512k
%:
%:Then use dd to pull in the last "part" of the tape which is your tar'd files:
%:
%:	$ dd if=/dev/rmt4 of=/tmp/damaged bs=512k
%...
%ALL THIS IS TECHNICALLY CORRECT BUT BOUND TO FAIL FOR TYPICAL CARTRIDGE
%TAPE STREAMERS, SINCE THESE DEVICES PHYSICALLY ERASE ALL OF THE TAPE
%WHEN WRITING THE FIRST TRACK!
%
%(IMHO the topic should go into the FAQ.)
%-- 
%Martin Weitzel, email: martin at mwtech.UUCP, voice: 49-(0)6151-6 56 83

I'm not sure I follow this...How can a drive "Physically Erase" a portion
of tape that has not passed under the head?  I've actually performed the 
above operation on a QIC-24 cartridge.

Dan
---