OS X has a number of options for handling disk images–settings for such things as automatically opening them, moving Internet-enabled images to the trash after opening, verifying checksums, and more. You control all of these options (and a few more) in Disk Utility’s preferences panel.
If you change these settings often, though, you may tire of launching Disk Utility and opening its preferences panel. As an alternative–and with a side bonus of gaining one additional option–you can install a hidden System Preferences panel to make accessing these options a bit easier. There are two ways to install this panel; one requires Terminal, and the other uses just the Finder. If Apple were to update the panel at some point, the Finder method wouldn’t reflect those updates, while the Terminal method always insures you’re seeing the latest version of the panel.
If you’d like the simple Finder solution, navigate to /System -> Library -> PrivateFrameworks -> DiskImages.framework -> Versions -> A -> Resources. In that folder, you’ll see a file named DiskImages.prefPane. Just double-click it, wait for System Preferences to launch, and then decide whether you’d like to install the panel just for your user, or for all users of the machine. Click Install and you’re done.
The Terminal method is also simple, though it looks a lot uglier. To insure that you’re always seeing the newest version of the file, instead of installing it by copying it (which is what the Finder method does), we’ll use Terminal to create a symbolic link (much like an alias in the Finder) between the original and an entry in your user’s Library -> PreferencePanes folder. (If you’d like to do this for all users instead, you’d use the top-level Library -> PreferencePanes folder.) Just copy and paste this command into Terminal (quit System Preferences first if it’s open):
ln -s /System/Library/PrivateFrameworks/DiskImages.framework/Versions/A/Resources/DiskImages.prefPane ~/Library/PreferencePanes/
Regardless of the method you used, when done, you’ll see the new Disk Images panel in the Other section of System Preferences. The panel simply modifies the settings as shown in Disk Utility’s preferences panel, with one exception. The exception is the new preference labeled Ignore Bad Checksums in the Mounting tab. If enabled, OS X will ignore any checksum errors and mount the disk image; typically, a bad checksum will prevent a disk image from mounting.
I strongly advise that you don’t enable this option, as checksums are at least one level of protection against hacked disk images. However, if you have a disk image that you know isn’t hacked (perhaps it’s one you created yourself), but that seems to be damaged and won’t mount, this setting might (with an emphasis on might) just let you mount it and at least copy some of the data off the image.
If you don’t modify your disk image handling options very often, this hint probably won’t save you a lot of time. But if you do a lot of work with disk images, you may find it useful.