To enable this feature you must expose Disk Utility's Debug menu, which Apple uses for testing the app's features during development. Here's how:
1. Quit Disk Utility
2. Open the Terminal utility
3. Run the following Command:
defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
4. Relaunch Disk Utility
With this menu enabled, choose the Show every partition command near the bottom and any hidden partitions will appear. You'll see, for example, an EFI partition appear on bootable drives and a Recovery HD partition for those drives that hold one. To undo this option, first deselect the Show every partition command, repeat the procedure above, and then run the following command in step 3:
defaults delete com.apple.DiskUtility DUDebugMenuEnabled
Verify and repair multiple items at once
This last tip is a matter of quick convenience, particularly if you regularly check drives for errors. To verify a drive you'd normally ensure that Disk Utility's First Aid tab was selected, choose an individual drive, and click the Verify Disk button in the bottom-right of the window. You'd then move on to another disk and repeat these steps. However, to speed things up you can verify more than one drive at a time, including all drives at once, if you wish.
To do this, simply hold down the Command key and, in the sidebar, select the volumes and disks that you want to verify (or press Command-A to select them all). Note that Select All means exactly what it says; you'll select mounted disk images and optical disks along with your drives, so be sure to deselect any you don't want to check by Command-clicking on them. With the desired devices selected you can then click Verify Disk. Disk Utility will then act on them in sequence.
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