title: Unable to join Docker swarm because control.sock is missing?
body: <p>I have an existing Docker swarm consisting of three machines. I am trying to add a new manager to this swarm. I run the command</p>
  <p><code>docker swarm join --token SWMTKN-1-&lt;...&gt; 192.168.200.200:2377</code></p>
  <p>After a while I get the error</p>
  <p><code>Error response from daemon: manager stopped: can't initialize raft node: rpc error: code = Unknown desc = could not connect to prospective new cluster member using its advertised address: rpc error: code = DeadlineExceeded desc = context deadline exceeded</code></p>
  <p>I view the daemon logs using <code>tail -f /var/log/messages | grep docker</code>, I see this:</p>
  <p><code>Mar 17 17:07:48 UAT-Blockchain dockerd: time=&quot;2021-03-17T17:07:48.575024542+08:00&quot; level=warning msg=&quot;grpc: addrConn.createTransport failed to connect to {/var/run/docker/swarm/control.sock  &lt;nil&gt; 0 &lt;nil&gt;}. Err :connection error: desc= \&quot;transport: Error while dialing dial unix /var/run/docker/swarm/control.sock: connect: no such file or directory\&quot;. Reconnecting...&quot; module=grpc</code></p>
  <p>A quick check shows that <code>/var/run/docker/swarm/control.sock</code> is indeed missing on this machine, but is present on the machines in the existing swarm.</p>
  <p>What is this <code>control.sock</code>? How should I go about enabling/reinstating it on this current machine? Is this a problem of faulty installation?</p>