In order to eliminate some of the permissions obstacles I keep finding, I decided to make it easier on myself. I did

$ sudo chmod 755 -R /usr

If I knew 10 hours ago what I've learned in researching this, I wouldn't have used that command. I tried this first

$ chmod 755 -R /usr

That resulted an a large number of these:

$ chmod: changing permissions of ‘/usr/dir/file’: Operation not permitted

I tried another sudo command, and that one returns:

effective uid is not 0, is sudo installed setuid root?

Is there a way to reverse this without a clean reinstall? All I've done for the last 8 or 9 days is to read, configure software, and try to learn how to use the terminal, and I don't exactly look forward to starting that process again, even if not quite back to the beginning.


Not really. It's technically feasible, but a clean reinstall will be easier to fix this kind of issue.

If you really want to go the hard way, you should boot a live CD and reinstall sudo on your installation. Then reboot and sudo should be working again, allowing you to reinstall all your broken packages, etc.

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    Plus, anything besides reinstalling runs the risk of not fully fixing the problem, and being unpleasantly surprised when things don't work right later. – Eliah Kagan Aug 18 '13 at 12:32

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