title: Preflight errors in Kubernetes installation
body: <p>I am referring to the following link <a href="https://linuxconfig.org/how-to-install-kubernetes-on-ubuntu-18-04-bionic-beaver-linux" rel="nofollow noreferrer">Installation Link</a> for installing Kubernetes on Ubuntu 18.04. I am getting the following errors on typing the command : </p>
  
  <pre><code>sudo kubeadm join 192.168.0.114:6443 --token qgce4f.tgzda1zemqnro1em --discovery-token-ca-cert-hash sha256:6ebc15a5a9818481f8a98af01a7a367ba93b2180babb954940edd8178548773a ignore-preflight-errors=All
  
  W0303 18:33:39.565868    7098 join.go:185] [join] WARNING: More than one API server endpoint supplied on command line [192.168.0.114:6443 ignore-preflight-errors=All]. Using the first one.
  [preflight] Running pre-flight checks
      [WARNING SystemVerification]: this Docker version is not on the list of validated versions: 18.09.3. Latest validated version: 18.06
  [preflight] Some fatal errors occurred:
  [ERROR DirAvailable--etc-kubernetes-manifests]: /etc/kubernetes/manifests is not empty
      [ERROR FileAvailable--etc-kubernetes-kubelet.conf]: /etc/kubernetes/kubelet.conf already exists
      [ERROR Port-10250]: Port 10250 is in use
      [ERROR FileAvailable--etc-kubernetes-pki-ca.crt]: /etc/kubernetes/pki/ca.crt already exists
  [preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-preflight-errors=...`
  </code></pre>
  
  <p>Can someone please tell me how to fix this? Thanks !</p>