Can not make a 6.2 ISO image

[doug]

My goal was to make an cdrom that I could use with a serial console. I 
downloaded an iso image, burned a cdrom and used that cd to make a file tree 
with:

    tar -cf - -C /mnt/ . | tar -xpf - -C 6.2-RELEASE/

The du command shows essentially the same size for the cdrom and the file tree:

    1020444 /mnt (cdrom)
    1053224 6.2-RELEASE/

The difference of about 31MB is almost entirely in /usr (24MB). I took this to 
be the difference in internal/external fragmentation between isofs and ufs. 
However mkisofs builds an ISO image of 1GB. Whatever my error is, it is not due 
to missing hard links (I think). The du sums and counting files with find all 
this matches.

I could not find anything in GNATS on mkisofs. Is there another way to build an 
iso image? If anyone can see what I did wrong or where my analysis is off I 
would really appreciate the help.