There are two levels of permissions assigned to the files, directories, and processes in Linux.
The first one is permission groups, which is otherwise referred to as the ownership. The three types of user groups are <code>owners</code>, <code>groups</code>, and <code>others</code>.
The second one is permission types, which can be <code>read</code>, <code>write</code>, or <code>execute</code>.
<ul>
<li><code>read</code>: <code>r</code></li>
<li><code>write</code>: <code>w</code></li>
<li><code>execute</code>: <code>x</code></li>
</ul>
<h2>Example</h2>
<pre><code class="language-bash">ls -l
</code></pre>
Response:
<pre><code>drwxr-xr-x 5 andre-jacquesdebeer staff 160 Aug 15 17:49 k8s
 12345678910
</code></pre>
Position meanings:
<ul>
<li><code>1</code> = item type
<ul>
<li><code>d</code> = <code>directory</code></li>
<li><code>c</code> = <code>character</code></li>
<li><code>s</code> = <code>socket</code></li>
<li><code>p</code> = <code>pipe</code></li>
<li><code>D</code> = <code>D</code></li>
<li><code>l</code> = <code>symbolic link</code></li>
</ul>
</li>
<li><code>234</code> =&gt; owner
</li>
<li><code>567</code> =&gt; groups
</li>
<li><code>8910</code> =&gt; others
</li>
</ul>
So <code>rwxr-xr-x</code> means the owner of the file (andre-jacquesdebeer) can read, write, and execute, group may read and execute (not write!) and others may read and execute (again, not write!)
<h2>Number form</h2>
<ul>
<li>0: No permission</li>
<li>1: Execute</li>
<li>2: Write</li>
<li>4: Read</li>
</ul>
Combinations:
<ul>
<li>rwx = 1+2+4 = 7</li>
<li>rw- = 2+4 = 6</li>
<li>r-x = 1+4 = 5</li>
<li>r-- = 4</li>
<li>-wx = 2+1 = 3</li>
<li>-w- = 2</li>
<li>--x = 1</li>
</ul>
Example:
<pre><code class="language-bash">sudo chmod 777 filename.txt
</code></pre>