To make an ISO from your CD/DVD, place the media in your drive but do not mount it. If it automounts, unmount it.
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
To make an ISO from files on your hard drive, create a directory which holds the files you want. Then use the mkisofs command.
mkisofs -o /tmp/cd.iso /tmp/directory/
This results in a file called cd.iso in folder /tmp which contains all the files and directories in /tmp/directory/.
For more info, see the man pages for mkisofs, losetup, and dd, or see the CD-Writing-HOWTO at http://www.tldp.org.
If you want to create ISO images from a CD and you’re using Windows, Cygwin has a dd command that will work. Since dd is not specific to CDs, it will also create disk images of floppies, hard drives, zip drives, etc.
For the Windows users, here are some other suggestions:
WinISO ~ http://www.winiso.com
VaporCD ~ http://vaporcd.sourceforge.net ~ “You can create ISOs from CD and mount them as ‘virtual’ CD drives. Works flawlessly with games and other CD based software.