This is helpful if you have 4 CD .isos (like an operating system distribution of CD 1 of 4, 2 of 4, 3 of 4, and 4 of 4) and you want just one .iso file on a single DVD disc for convenience purposes.

Create the separate .iso files and put them into 1 temporary directory by using:

dd if=/dev/cdrom of=filename.iso

check creation is okay with:

sum -r /dev/cdrom
sum -r <filename.iso>

Now copy make.dvdiso.bash into that directory, and call it like this (use the 'export' command if the script has .bash extension?):

export _POSIX2_VERSION=199209
./make.dvdiso /iso/dir/path output_image_name.iso

that creates the .iso file.
Now you can burn it to DVD using other software, such as Roxio, Nero, or Sonic.