title: Mongodb 4: Failed to start mongod.service: Unit mongod.service not found
body: <p>I am trying to install mongodb 4 on Ubuntu 15.10 but its giving me this error when I start mongod:</p>
  
  <pre><code>Failed to start mongod.service: Unit mongod.service not found
  </code></pre>
  
  <p>I followed this official installation guide:</p>
  
  <p><a href="https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/" rel="nofollow noreferrer">https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/</a></p>
  
  <p>There is no official installation instructions for Ubuntu 15.10</p>
  
  <p>I was successfully able to install on Ubuntu 16 but I am getting issues on Ubuntu 15.10.</p>