This morning while working on getting a CentOS Jumpstart Server setup with a Knoppix rescue boot image I ran across the following simple utility mkisofs. It was not installed on my box so I had to get it via yum.

In the example below I created an iso from a directory knoppix51
mkisofs -o knoppix51.iso knoppix51

Below are the common usage options:

mkisofs [-a] [-b boot_image] [-c boot_catalog]
        [-A application_id] [-f] [-d] [-D] [-i include-list]
        [-l] [-L] [-p preparer] [-P publisher] [-r] [-R]
        [-T] [-v] [-V] [-V volid] [-x path] [-z] [-m glob]
        -o filename path

Here is how to use mkisofs to make an iso from a cd/dvd

  dd if=/dev/dvd of=dvd.iso    # for dvd
 
dd if=/dev/cdrom of=cd.iso   # for cdrom
 
dd if=/dev/scd0 of=cd.iso    # if cdrom is scsi

You can also download it from http://freshmeat.net/projects/mkisofs/