To create iso image from a CD/DVD in Linux (thank you lifehacker.com):

 

Turn a CD/DVD into an .iso
sudo umount /dev/cdrom
dd if=/dev/cdrom of=file.iso bs=1024
Turn a folder into an .iso
mkisofs -r -o file.iso /location_of_folder/
Generate an MD5 checksum file
md5sum file.iso > file.iso.md5

 

 To write a iso to a CD:

 

When you insert CD, exit out of the auto write wizard.  Right click on iso image and select "Write to disc."