title: What do "!" and "*" mean in the password section in /etc/shadow?
body: <p>In a /etc/shadow file, it looks like as follows.</p>
  
  <pre><code>root:!:15764:0:99999:7:::
  daemon:*:15749:0:99999:7:::
  </code></pre>
  
  <p>What do these characters ("!" and "*") mean in the password section?</p>