Using cpio and a tape drive

[spotter at desire.wright.edu]

I have a question concerning using cpio to store files on a tape drive.  I have
just been learning this process so that I can teach those here at work how to
do it.  I thought I had it working, until I quit, came back and tried to put
more files on the tape.  It went to the beginning of the tape and started from
the beginning, erasing everything I already had on there.  Is there an option
that can be used to make cpio read to the last file, and begin after it?  Or
can I never put more files on a tape without destroying the old ones? 

Thanks you,
Stephen Potter
spotter at desire.wright.edu  <==soon maybe changing to presto at desire
spotter at eve.wright.edu