How to Fix Mac OS X File Permissions

Mac OS X System AdministrationThis blog post will show you how to fix Mac OS X file permissions that may have been set incorrectly. For the most part Mac users don’t need to worry about file or folder permissions. You can normally go about your business and Mac OS X will take care of managing the proper file permissions as you create and modify files on your Mac. There are a few cases however, such as copying files from other user accounts, when file or folder permissions may get set incorrectly. This can cause a variety of issues and symptoms including the following.

  • Being unable to rename, modify, move or delete files that you should be able to.
  • Programs failing to save settings or preference changes. For example you may make changes to a program and when you relaunch it later you notice that the changes didn’t stick.
  • Programs failing to launch or operate correctly. While this may sometimes happen due to permissions issues, such behavior could also be due to other issues, such as disk or data corruption.

The simplest way to check and/or modify a file or folder’s permissions on Mac OS X is through the Get Info window. Simply select the file or folder in question and choose the Get Info command from the File menu or right-click on the file or folder and choose Get Info from the pop-up menu that appears.

At the bottom of the Get Info window is the Sharing & Permissions section. Clicking the little gray triangle widget to the left of Sharing & Permissions: will expand/collapse the section. This section is simply a graphical user interface (GUI) to display and control the underlying Unix file permissions system. In its simplest state these permissions consist of a set of single owner, group and everyone settings. In more complex cases there could be multiple entries for owners or groups using a Unix mechanism called Access Control Lists (ACLs).

There is more in-depth information about using Mac OS X Unix underpinnings in these books on Amazon.

Proper Mac OS X Home Folder & Library File Permissions

How to Fix Mac OS X File Permissions - Default User File Permissions

Default User File Permissions
  • Owner: UserX (Me) — Read & Write
  • Group: staff — Read only
  • everyone — Read only

How to Fix Mac OS X File Permissions - Default User Library Permissions

Default User Library File Permissions
  • Owner: UserX (Me) — Read & Write
  • everyone — No Access

How to Fix Mac OS X File Permissions - Default System Library Permissions

Default System Library File Permissions
  • Owner: system — Read & Write
  • Group: wheel — Read only
  • everyone — Read only

How to Fix Mac OS X File Permissions

If you’ve copied files from a different user account into your user account sometimes you may find that you can not rename, modify, move or delete the files without entering an administrator password. Examining the files permissions in the Get Info window will often show the following strange result, 2 entries for everyone with one of them set to custom. This second everyone entry is an ACL entry that causes the file to be read-only. Even though you may be listed as the owner with read/write access it may say You have custom access at the top.

How to Fix Mac OS X File Permissions - Bad File Permissions

Bad File Permissions
  • everyone — Custom
  • Owner: UserX (Me) — Read & Write
  • Group: staff — Read only
  • everyone — Read only

Before making any changes to file or folder permissions you should first back up all data on your Mac. Setting the permissions incorrectly could render your Mac unusable and/or cause loss of data. Proceed at your own risk.

To make changes to the permissions in the Get Info window first click on the lock in the bottom right corner and enter an administrator user name and password. You may then use the + and buttons in the bottom left corner to add or remove names from the permissions list. Clicking on any of the associated privileges opens a pop-up menu to select Read & Write, Read only, or No access (only available for “everyone”).

To fix the above example of two everyone settings preventing you from modifying a file you would select the everyone permission that’s set to Custom (the ACL entry) and delete it using the button.

If you make a mistake setting the permissions on a single file or folder, you may be able to reverse the changes by selecting the Revert Changes command in the gear pop-up menu at the bottom.

To change the permissions of a folder and ALL the files and folders that it contains you may use the Apply to enclosed items… command in the gear pop-up menu. BE VERY CAREFUL WITH THIS HOWEVER. A warning will pop-up because you can’t undo this, so be very sure you know exactly what you are doing in this case. I’d avoid doing this to any high level folder because it will drill the change down to each and every folder and file contained within, recursively.

Sometimes you may be able to correct the file and folder permissions using these controls in the Get Info window. In some cases however, such as removing ACLs that have been added to files/folders due to copying them from another user account, this may not work through Get Info alone. In such cases you may drop into Unix and make the changes manually in the Terminal if you are comfortable managing permissions directly in Unix. This can be tricky and error-prone if you aren’t comfortable working directly in Unix however. In such cases it is much easier to use the free donation-ware BatChmod or the shareware FileXaminer.

BatChmodIn BatChmod simply drag the file or folder in question to the File… field. Then turn OFF Change ownership and privileges and turn ON Clear ACLs (10.5+). If this is a folder and you want to remove the ACLs from the entire contents of the folder and all subfolders (be careful) then also turn ON Apply to enclosed folders and files. Then click the Apply button.

How to Fix Mac OS X File Permissions for the Entire Home Folder

If all else fails and your home folder is messed up you can try to reset the user’s Home folder permissions and ACLs back to the defaults. After backing up all data on the Mac, proceed at your own risk with the following steps.

  • Restart the Mac into Mac OS X Recovery Mode by holding down Command-R as the Mac restarts.
  • Open Terminal from the Utilities menu.
  • Type the following command into terminal, all one word, and press the return key.
  • This will open the Reset Password window which includes a section at the bottom labeled: Reset Home Directory Permissions and ACLs. Click the Reset button.
  • When the Reset button changes to Done, select Restart from the Apple menu.

How to Fix Mac OS X File Permissions for the Entire Home Folder

There is more in-depth information about using Mac OS X in these books on Amazon.

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