Disk Utility (Yosemite): First Aid pane
The First Aid pane lets you verify your disk is in good condition. If any issues are found they are listed. You can then repair the problems found.
Note: You can’t repair write-protected disks, CDs, or DVDs.
Your disk may need repair if you experience certain problems, for example, problems with permissions, corrupted files, or booting issues that may prevent the computer from starting up.
Last Modified: Feb 20, 2015