useing mkisofs to make iso from cd.
 

how do i use mkisofs a make an iso from a data disk.

If you have the cdrom in postition /mnt/cdrom, you need to mount it first.
mount /mnt/cdrom
change to that directory
cd /mnt/cdrom
Now you can make the iso. In this case, just a data iso and not a bootable one....
mkisofs -R -J -o /home/mycd.iso .
Note: In this case, the period ( . ) is important.
umount /mnt/cdrom

If you want to make a bootable cdrom from the iso, you will need a boot image in there.

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