Create ISO images from CD, DVD & Folder

For Drives

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

For Folders

sudo apt-get install genisoimage
mkisofs -allow-lowercase -o cd.iso image/