mkisofs is a pre-mastering program to generate an ISO 9660 file
system.  It takes a snapshot of a directory tree, and makes a binary
image which corresponds to an ISO 9660 file system when written to a
block device. It supports the Rock Ridge Interchange Protocol for
preserving Unix file system information under the ISO 9660 format.

mkisofs was modified in the cdrtools package, but there are licensing
issues with that package, and it is not part of GNU.

The original GNU mkisofs is available from
  http://www.tux.org/pub/people/eric-youngdale/mkisofs/
and we are seeking volunteers to modernize it, perhaps integrating with
GNU libcdio and/or GNU vcdimager.

See http://www.gnu.org/software/libcdio for more info.