Mac OS X Permissions

Despite its colourful exterior it's always worth remembering that Mac OS X is a very powerful Unix-based operating system. Underneath the hood is a complex OS with careful control over who gets to do what.

These are called Permissions. Every file and every user has permissions set to it. And what to do if Mac OS X suddenly says "You don't have permission" to look at, move, or delete a file is something our readers often ask.

Permissions are closely aligned with user accounts and also whether an account is an Admin or User account (or a type known as Root, which you shouldn't use unless you really know what you're doing and then only briefly).

In this feature we'll look at how to adjust permissions for individual files. And how (and when) you should repair permissions using Disk Utility.

Read also: How to defrag and speed up your Mac

Mac OS X Permissions versus Hidden and locked files

Every single file in Mac OS X has a permission attached to it according to the type of user. You can see this by highlighting a file, clicking Command+I and going down to the bottom of the window to look at Sharing and Permissions.

There are three specific Privilege levels that control permission to use files in Mac OS X:

  • Read Only
  • Read and Write
  • No access

You can set these for different users, or account types. You can pick be Admin, Everyone, a specific account or an individual user. It is possible to adjust the permissions for each file, by clicking the Lock icon, entering your password and then select a different Privilege

Mac OS X Permissions and Privileges

What do I do if it says "You don't have permission..."?

If you don't have permission to access a file, folder, or external hard drive then it's typically because it was created by another user account and you're trying to access it. If it's just an individual file then follow these steps.

  1. Highlight the file and click Command+I
  2. Click the Lock icon in the bottom right and enter your account password.
  3. Click the '+' icon
  4. Select your account from the "Users & Groups" window
  5. Click Select

If it's a folder or entire drive, and you wish to access sub-folders. Then do the following..

  1. Click the Cog icon
  2. Choose Apple to Enclosed Items
  3. Click Okay

Not that it's possible to revert Permission changes to individual items but not entire folders or drives.

Repairing Permissions with Disk Utility

Most of the time if you have difficulty with Permissions it's because the permissions attached to files overall need fixing. Problems with Permissions can cause random errors, such as programs not opening, logging in to accounts, printing, and starting up.

You can Repair Permissions using Disk Utility. It's worth noting that Repairing Permissions has joined classic catch-all repairs such as "Zapping the PRAM" and "Rebulding the Desktop". Because permissions cause a wide range of random issues, it tends to be used to attempt to fix just about anything. These are classic reach-tos for many Mac users experiencing random problems. As such it tends to be over-used, but as far as we know it causes little problems.

To repair Permissions first open the Disk Utility app (located in Applications/Utilities). Select the Disk from the sidebar (typically it's the Startup disk) and click First Aid. Now click the Repair Disk Permissions. It will almost certainly find something to repair, and it may well help you with your problem.

Repairing Permissions in Disk Utility

Permissions can also be repaired via the Terminal by using the command:

sudo diskutil repairPermissions /

Using the Repair Permissions command is something every Mac OS X user should know how to do. It's a good fix for many problems. Although it doesn't fix everything, it's certainly a good tool to have in your toolbox.