<h3>Version</h3>
<ol>
<li>k8s version: v1.19.0</li>
<li>metrics server: v0.3.6</li>
</ol>
<p>I set up k8s cluster and metrics server, it can check nodes and pod on master node,
work node can not see, it return unknown.</p>
<pre><code>NAME    CPU(cores)   CPU%   MEMORY(bytes)   MEMORY%
u-29    1160m        14%    37307Mi         58%
u-31    2755m        22%    51647Mi         80%
u-32    4661m        38%    32208Mi         50%
u-34    1514m        12%    41083Mi         63%
u-36    1570m        13%    40400Mi         62%
</code></pre>
<p>when the pod running on the client node, it return <code>unable to fetch pod metrics for pod default/nginx-7764dc5cf4-c2sbq: no metrics known for pod</code>
when the pod running one the master node, it can return cpu or memory</p>
<pre><code>NAME                     CPU(cores)   MEMORY(bytes)
nginx-7cdd6c99b8-6pfg2   0m           2Mi
</code></pre>

benq
<p>This is a community wiki answer based on OP's comment posted for better visibility. Feel free to expand it.</p>
<p>The issue was caused by using different versions of docker on different nodes. After upgrading docker to v19.3 on both nodes and executing <code>kubeadm reset</code> the issue was resolved.</p>
