Gas station without pumps

2011 November 20

Breaking every application on Mac OS X

Filed under: Uncategorized — gasstationwithoutpumps @ 00:34
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John Burk, in his blog post Designing a new type of tech PD-feedback wanted, said

“There is almost nothing you can do from the keyboard to harm or permanently damage your computer.”

Ah, if only that were true. It took several days of debugging to get my son’s account working on our new Mac again, after he did something seems innocuous: changed “Sharing and Permissions” on his home directory and did “apply to enclosed items”. He had done it because he’d created a new crippled account for himself with parental controls that prohibited his favorite time wasters, but he wanted that account to have access to all his files on his regular account.  He gave the crippled account read and write access to his home directory and clicked the button to propagate that recursively.

We spent days trying to figure out why almost every application program (TextEdit, Pages, Photoshop Elements) was broken and how to fix it. The programs all worked on the other accounts, so it was clear that the problem was specific to his account. Just figuring out that it was changing the permissions on the home directory that broke everything took a while, though we pretty quickly saw that the permissions were messed up on his files (with “everyone” appearing twice and the owner not having access, for example).

It turns out that Apple did one of the worst possible implementations of Access Control Lists (ACLs), so that changing the permissions on your home directory messes everything up. The secret fix is to remove all the ACLs with

chmod -R -N ~

You won’t find that advice from Apple, but from disgruntled users trying to figure out why their user-friendly Mac no longer does anything right.

This is not a new Lion bug, but one that has been around for a while. I’m amazed that they have left something so damaging in the system for so long.

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