The data in a disk image can be corrupted if a problem occurs while it’s being copied or if someone modifies it. You can see whether a disk image’s data has been corrupted by verifying its checksum, which is a calculation of all of its data. When a disk image is created, a checksum is computed and stored with the image. When you open the disk image, a checksum can be computed again and checked against the stored checksum. If the two checksums match, the disk image’s data hasn’t been corrupted.

You can choose when to compute and verify checksums. Be aware that doing so can take a long time.

Open Disk Utility for me

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What version of OS X are you running? Have you done all the "voodoo" repairs, like running a "Repair Permissions" procedure?

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Well I'm not really sure what to do I'm a first time Mac user so.. And I don't know anything about the repair procedure. I'm using OS X Lion

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Open your Applications folder, then Utilities. Open Disk Utility, select your hard drive, and click Repair Disk Permissions.

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Open your Applications folder, then Utilities. Open Disk Utility, select your hard drive, and click Repair Disk Permissions.

1. Go to the /usr/bin/ folder (you’ll need to make sure Show Hidden items is activated in Finder’s View menu (if you don’t have that option, look up online how to turn on hidden files, or install XtraFinder). Or just use the Go menu in Finder, then Go to folder,and past in /usr/bin/

2. Locate the file called codesign

3. Rename it to codesign.1094 (just tack .1094 on the end of the file name)

You will need to enter you system password (the one you use to log into your computer with). You will need to do this at various stages in this process, so just go ahead a enter it each time.

4. Drag or copy/paste the downloaded codesign file into the /usr/bin/ folder.

The end result will look something like this: (ignore the codesign.je file—that was me testing another solution to this issue)

You should now be able to open your troublesome apps and patchers.

Security Warning

For the average Apple user, I don’t recommend leaving this 10.9.4 codesign file in place. Use it for what you need to get done, and then rename it to something like codesign.1094 and then take the 1095 off the original file you named codesign.1095 at the beginning of this process. Basically, put things back to how they were. There’s no problem leaving a copy of the codesign.1094 file in that /bin folder, in case you need it again.

Of course, if you feel comfortable foregoing Apple’s pre-cautious code-signing changes, then leave the 10.9.4 file there if that suits you better. I see no reason to though.

UPDATE: Translating a page I found in German, I gather the “patchers” referred to by the above-mentioned error message are “Special K” software patchers (to get around registration requirements, etc.). I can’t tell if there are legal “patchers” but since the OS X generated error message refers to “patchers” I can only assume there must be.

If you’ve ever downloaded an application from anywhere other than the Mac App Store, then it’s likely it came packaged as a compressed disk image. That’s a very useful and convenient way for developers to make applications available and works very well, most of the time. Occasionally, however, you may see a message telling you that ‘the following disk images could not be opened…’ That usually happens because the disk image is corrupt. Here’s what to do if that happens.

What is a disk image?

A disk image on Mac is a file format that mimics a physical disk. Like physical disks, it can be mounted in Finder, where it looks like any other volume, have files and folders copied to and from it, and can be cloned or burned onto physical media like a CD or DVD. Disk images are ejected in the same way as physical disks and show up in Disk Utility. You can also use Disk Utility to create disk images of your own.

Disk images were originally used to distribute software remotely because the resource forks used by Mac applications couldn’t be transferred easily over networks like the internet. The introduction of Mac OS X meant resource forks were no longer used; however, disk images are still a popular way to distribute software. That’s largely because they allow the developer to control how the software is presented when the image is opened. For example, if you’ve ever downloaded an app that displays an image directing you to copy the app binary to your Applications folder, complete with an alias of the Applications folder, that’s only possible with a disk image.

What to do when you see the message “The following disk images couldn’t be opened”

The first step is to try re-downloading the disk image if you can. It may be that something happened during the download and corrupted the file. If re-downloading doesn’t work, and the disk image mounter on your Mac doesn’t work, you should use Disk Utility to verify the image.

1. Go to Applications > Utilities and open Disk Utility.
2. Click Images in the menu and choose Verify.
3. Navigate to the disk image in your Downloads folder or wherever it is saved.
4. Press Verify.
5. If the disk image verifies successfully, try opening it again.
6. If it doesn’t verify successfully, even after you’ve re-downloaded it, contact the developer.

How to deal with problems installing and running apps on your Mac

Sometimes, when you can’t open a disk image, the problem isn’t with the disk image itself but with your Mac. Files that have accumulated on your boot drive can cause conflicts and prevent disk images from opening or applications from running correctly. CleanMyMac X’s Maintenance module can help resolve these issues. It can repair disk permissions, free up RAM, and run maintenance scripts. Here’s how it works.

1. Download CleanMyMac X if you still don’t have it on your Mac. Then, install and open it.
2. Choose the Maintenance module from the sidebar.
3. Select the routines you want to run and Run.

Once you’ve run the maintenance routines, you should find that your Mac runs more quickly and smoothly.

Disk images are virtual disks that are widely used to distribute software. They date back to pre-OS X times when the resource forks used by Mac applications could be easily transferred over networks. Wrapping software in a container that replicated physical media allow it to be transferred. They also allow developers to control how applications look when they are first opened after being downloaded. However, occasionally, they become corrupt or run into problems. If you find that a disk image is not opening, follow the steps above to fix it. You can also use CleanMyMac X’s Maintenance module to run regular maintenance on your Mac and keep it running smoothly.