Disk Utility, a utility program that comes standard on all modern Mac computers, allows users to create DMG and ISO files and burn them as bootable disks, according to MacWorld. This process will work with any CD and DVD burnt properly in Disk Utility and is a handy way to make a backup of your Mac's OS or your current hard drive.
Open Disk Utility on your Mac computer. It is in the Applications/Utilities folder.
Select "New Image" and select the folder or drive you want to create a DMG or ISO file for. Insert a CD or DVD and select it if you want a bootable copy of one of those. Select the size and encryption. Choose "CD/DVD Master" as the format and click "Create."
Select the file that has been created from the Disk Utility window and click "Burn." Insert a CD-R or DVD-R and click "Burn."
You can also copy the bootable DMG file to a flash drive or an external hard drive after you create it with Disk Utility.