Comment 6 for bug 468809

Actually what you would have to do is:

1/ use the --copy option to copy your deb in the image
2/ use the --execscript to launch a script that
  * chroot $1
  * dpkg -i <yourdeb>

Does not sounds like much tinkering to me, but agree that we could consider this a wishlist item to allow for a --add-deb option. Not very hard to implement, btw.

On the documentation chapter, both --copy and --execscript do appear when I either do a 'man vmbuilder' or 'sudo vmbuilder kvm ubuntu --help', so I do not really understand your remark.