Permissions are file settings that affect the ability to read, write, or execute (open or run) the file. If a file's permissions are no longer set correctly, software that uses the file might not work correctly. You can see a file's permissions in the Sharing & Permissions section of its Get Info window.
Beginning with OS X El Capitan, system file permissions are automatically protected. It's no longer necessary to verify or repair permissions with Disk Utility.
Follow these steps in OS X Yosemite or earlier:
- Open Disk Utility, which is in the Utilities folder of your Applications folder.
- Select the startup disk from the list of volumes.
- Click the First Aid tab.
- To check permissions, click Verify Disk Permissions. To repair permissions, click Repair Disk Permissions.
Disk Utility checks a file's permissions only if the file has a corresponding receipt in /var/db/receipts. The receipt tells Disk Utility what the permissions should be. Not all installers include a receipt with the files they install.