[OT] How to fix a stupid chmod mistake without rebooting

[Thorny]

On Fri, 27 Mar 2009 23:45:30 -0400, Matthew Flaschen posted:

> For reasons I'm not entirely clear, / was world-writable on a machine (not
> the whole computer, just /). So I blithely ran:
> 
> sudo chmod go-rwx /
> 
> (note, no -R, I'm not *that* dumb).
> 
> to correct it (can't be giving out permissions willy nilly!).
> 
> Then, to admire my handiwork I did:
> 
> ls
> zsh: command not found: ls
> 
> That's odd... (repeat ls several times in hope results will change). Start
> typing /bi hit tab to complete instinctually, zsh auto-complete prints
> errors like: (eval):3: permission denied: /dev/null
> 
> Finally realize what is happening (almost)
> 
> Try:
> 
> su
> 
> to go to root to fix it.
> 
> zsh: command not found: su
> 
> So by this point I am rather unhappy, and wondering if I'm going to break
> out a rescue CD.  But of course, I had root enabled on this machine, so I
> finally remembered the virtual terminal (already running login) could save
> me:
> 
> Login as root.  Enter:
> 
> sudo chmod a+rx /
> 
> Save the day.
> 
> Lessons (pick any two)
> 
> 1. Keep root enabled
> 2. sudo will not stop you from making stupid decisions. 3. Don't run sudo
> chmod a-rwx /
> 

Scary!

I can't write from experience because I have never tried anything like
that. However, I wonder why you didn't try "ugo" instead of just "go", it
is my understanding that one either uses "ugo" or 1, and only 1 of
the options. I also think that "a" is default if no option is used.

Glad you had the presence of mind to be logical and reason how to back out
of the situation.