Change permission on /usr with a sudo chmod 644 /usr
<p>I am a trainee programmer and I have sometimes my head in the clouds..</p>

<p>My collegues were messing with my professional computer with ssh connections. One of them told me that the best way to prevent it was to secure my computer. In order to do this, I accidentally change the permissions on the /usr directory.
What I did just for testing was :</p>

<pre><code>sudo chmod 644 /usr
</code></pre>

<p>Now I can't use my computer anymore! I can't change the permission back since I am not sudo anymore. On my desktop all my applications shutdown.
Is there a way to revert a chmod 644 on /usr? </p>

<p>There is some important work related stuff on this computer and my internship will probably be terminated if I can't recover the access to important files.</p>

<p>Please help !!</p>