title: When I(root) excute "usermod -G sudo chauncey",it say that "sudo group doesn't exist"
body: <p>OS: CentOS 7. When I (root) execute the command below, it says that "sudo" group cannot be found.</p>
  
  <pre><code>[root@localhost etc]# usermod -G sudo chauncey
  usermod：“sudo” group doesn't exits
  </code></pre>
  
  <p>I also check file in <code>/etc/group</code>, and "sudo" doesn't exists in it. So, how can I create a "sudo" group correctly?</p>