title: Adding Debian 9 (Stretch) Backports to my sources.list
body: <p>I am trying to secure a website by using Certbot, the issue I'm having is regarding the "stretch-backports"
  This is the line of code certbot asks of me, however I get an error saying "stretch-backports" isn't part of the available sources.</p>
  
  <pre><code>$ sudo apt-get install certbot -t stretch-backports
  </code></pre>
  
  <p>So I tried adding the backports with this line:</p>
  
  <pre><code>deb http://ftp.debian.org/debian stretch-backports main
  </code></pre>
  
  <p>But "deb" was not recognized. So I installed gdebi which is similar:</p>
  
  <pre><code>sudo apt-get install gdebi
  </code></pre>
  
  <p>With that installed, I tried the previous line again with a slight modification:</p>
  
  <pre><code>gdebi http://ftp.debian.org/debian stretch-backports main
  </code></pre>
  
  <p>And now it says "gdebi error, file not found: <a href="http://http.debian.net/debian" rel="noreferrer">http://http.debian.net/debian</a>"</p>
  
  <p>So my question is twofold, if I didn't mess up in the previous steps, does someone have and functional address for the stretch-backports and is gdebi a good substitue for deb?</p>
  
  <p>Thank you in advance.</p>