<p>The status of nodes is reported as <code>unknown</code></p>

<pre><code>"conditions": [
          {
            "type": "Ready",
            "status": "Unknown",
            "lastHeartbeatTime": "2015-11-12T06:03:19Z",
            "lastTransitionTime": "2015-11-12T06:04:03Z",
            "reason": "Kubelet stopped posting node status."
          }
</code></pre>

<p>whle <code>kubectl get nodes</code> return a NOTReady status. What does this imply and how to fix this?</p>

<h3>Get nodes</h3>

<pre><code>kubectl get nodes
</code></pre>

<p>Result:</p>

<pre><code>NAME            STATUS     AGE
192.168.1.157   NotReady   42d
192.168.1.158   Ready      42d
192.168.1.159   Ready      42d
</code></pre>

<h3>Describe node</h3>

<p>Here is a <strong>NotReady</strong> on the node of <code>192.168.1.157</code>. Then debugging this notready node, and you can read offical documents - <a href="http://kubernetes.io/docs/user-guide/introspection-and-debugging/" rel="noreferrer">Application Introspection and Debugging</a>.</p>

<pre><code>kubectl describe node 192.168.1.157
</code></pre>

<p>Partial Result:</p>

<pre><code>Conditions:
Type          Status          LastHeartbeatTime                       LastTransitionTime                      Reason                  Message
----          ------          -----------------                       ------------------                      ------                  -------
OutOfDisk     Unknown         Sat, 28 Dec 2016 12:56:01 +0000         Sat, 28 Dec 2016 12:56:41 +0000         NodeStatusUnknown       Kubelet stopped posting node status.
Ready         Unknown         Sat, 28 Dec 2016 12:56:01 +0000         Sat, 28 Dec 2016 12:56:41 +0000         NodeStatusUnknown       Kubelet stopped posting node status.
</code></pre>

<p>There is a <strong>OutOfDisk</strong> on my node, then <strong>Kubelet stopped posting node status.</strong>
So, I must free some disk space, using the command of <code>df</code> on my <em>Ubuntu14.04</em> I can check the details of memory, and using the command of <code>docker rmi image_id/image_name</code> under the role of <code>su</code> I can remove the useless images.</p>

<h3>Login in node</h3>

<p>Login in <code>192.168.1.157</code> by using <em>ssh</em>, like <code>ssh administrator@192.168.1.157</code>, and switch to the 'su' by <code>sudo su</code>;</p>

<h3>Restart kubelet</h3>

<pre><code>/etc/init.d/kubelet restart
</code></pre>

<p>Result:</p>

<pre><code>stop: Unknown instance: 
kubelet start/running, process 59261
</code></pre>

<h3>Get nodes again</h3>

<p>On the master:</p>

<pre><code>kubectl get nodes
</code></pre>

<p>Result:</p>

<pre><code>NAME            STATUS    AGE
192.168.1.157   Ready     42d
192.168.1.158   Ready     42d
192.168.1.159   Ready     42d
</code></pre>

<p>Ok, that node works fine.</p>

<p>Here is a reference: <a href="https://opensource.ncsa.illinois.edu/confluence/display/~lambert8/Kubernetes" rel="noreferrer">Kubernetes</a></p>
