How-to: Burning disk images

One of the many benefits of Mac OS X is the built-in support for a variety of disk image formats, including ISO, IMG, CDR, and the popular DMG. Disk images are exceptionally useful for storing small sets of files, such as packaging applications for distribution. The convenience of disk images is that when you open them, they mount like you've just inserted a CD or DVD, instead of being just a file or folder on the disk, or unzipping contents to another location as is the case with compressed archives. As such, you can have a library of music, program installers, and personal information all arranged in disk images, and you have an option to encrypt them.

So why burn them? Often, items are distributed in disk image format for ease. This is especially true for software, which often requires installation from some sort of packaged media (CDs being the default). To mimic CDs, software is distributed on disk images that you can mount and install from. However, you may wish to burn the disk image to a physical disk and have your own installation media. In the Finder, if you drag the disk image to an inserted, blank DVD or CD, it will burn the disk image as a file to the DVD or CD, requiring you to manually mount it. Additionally, if you mount a disk image and try copying all the files on it directly to a disk to burn, you will not get all the hidden files and in the case of bootable disks (OS installation media, for instance) you will not properly copy the boot information.

Using Disk Utility, you can easily burn disk images to media that supports them. The following procedure will do it:

1. Launch Disk Utility
2. Click the "Burn" button (or just press command-B)
3. Locate the image file in the window and check the size of the image (under 750MB for CD, under 4.4GB for DVD, and under 7.9GB for DVD-DL)
4. Click "Burn" and the program will prompt you for a disk, insert one of the appropriate size and close the tray (not required for slot-loading players)
5. Test the media by inserting it after it is automatically ejected.

Optionally you can drag the disk image to the left-hand list of the Disk Utility window, highlight it, and click the "Burn" button. This has the added benefit of being able to access the disk image quickly, in case you need to make multiple burns of the image. To remove the image, highlight it and press the delete key.

While Disk Utility is a robust burning program that can handle the majority of burning jobs, it sometimes does not handle certain disk images very well. There are a variety of third-party image burning utilities that may handle image files differently than Disk Utility and be successful when Disk Utility runs into problems. Some recommendations are: Toast Titanium, Dragon Burn, Disco, and FireStarter.

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