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<section id="kubernetes">
<span id="id1"></span><h1>Kubernetes*<a class="headerlink" href="#kubernetes" title="Link to this heading"></a></h1>
<p>This tutorial describes how to install, configure, and start the <a class="reference external" href="https://kubernetes.io/">Kubernetes
container orchestration system</a> on Clear Linux* OS.</p>
<p>A Kubernetes cluster can be setup on Clear Linux OS using the Clear Linux OS cloud-native-setup
scripts to automate the process or can be setup through a manual step-by-step
process. This tutorial covers both scenarios.</p>
<nav class="contents local" id="contents">
<ul class="simple">
<li><p><a class="reference internal" href="#background" id="id6">Background</a></p></li>
<li><p><a class="reference internal" href="#prerequisites" id="id7">Prerequisites</a></p></li>
<li><p><a class="reference internal" href="#set-up-kubernetes-automatically" id="id8">Set up Kubernetes automatically</a></p></li>
<li><p><a class="reference internal" href="#set-up-kubernetes-manually" id="id9">Set up Kubernetes manually</a></p></li>
<li><p><a class="reference internal" href="#initialize-the-master-node" id="id10">Initialize the master node</a></p></li>
<li><p><a class="reference internal" href="#use-your-cluster" id="id11">Use your cluster</a></p></li>
<li><p><a class="reference internal" href="#troubleshooting" id="id12">Troubleshooting</a></p></li>
<li><p><a class="reference internal" href="#reference" id="id13">Reference</a></p></li>
</ul>
</nav>
<section id="background">
<h2><a class="toc-backref" href="#id6" role="doc-backlink">Background</a><a class="headerlink" href="#background" title="Link to this heading"></a></h2>
<p>Clear Linux OS has builtin integrations to make setting up Kubernetes using a variety of
<a class="reference external" href="https://kubernetes.io/docs/setup/production-environment/container-runtimes/">container runtimes</a>.</p>
<p>For more background information see:</p>
<ul class="simple">
<li><p><a class="reference internal" href="#what-is-kubernetes">What is Kubernetes?</a></p></li>
<li><p><a class="reference internal" href="#what-is-a-container-network-interface-cni">What is a Container Network Interface (CNI)?</a></p></li>
<li><p><a class="reference internal" href="#what-is-a-container-runtime-interface-cri">What is a Container Runtime Interface (CRI)?</a></p>
<ul>
<li><p><a class="reference internal" href="#what-is-cri-o">What is CRI+O?</a></p></li>
<li><p><a class="reference internal" href="#what-is-containerd">What is containerd?</a></p></li>
<li><p><a class="reference internal" href="#what-is-docker">What is Docker?</a></p></li>
</ul>
</li>
<li><p><a class="reference internal" href="#what-is-kata-containers">What is Kata Containers*?</a></p></li>
</ul>
</section>
<section id="prerequisites">
<h2><a class="toc-backref" href="#id7" role="doc-backlink">Prerequisites</a><a class="headerlink" href="#prerequisites" title="Link to this heading"></a></h2>
<p>This tutorial assumes you have already installed Clear Linux OS. For detailed
instructions on installing Clear Linux OS on a bare metal system, follow the <a class="reference internal" href="../get-started/bare-metal-install-desktop.html#bare-metal-install-desktop"><span class="std std-ref">bare
metal installation tutorial</span></a>.</p>
<ol class="arabic">
<li><p>Review and make sure the <a class="reference external" href="https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/install-kubeadm/#before-you-begin">requirements for kubeadm</a>
are satisfied for the host system.</p></li>
<li><p>Before you continue, update your Clear Linux OS installation with the following
command:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>swupd<span class="w"> </span>update
</pre></div>
</div>
<p>Learn about the benefits of having an up-to-date system for cloud
orchestration on the <a class="reference internal" href="../guides/clear/swupd.html#swupd-guide"><span class="std std-ref">swupd</span></a> page.</p>
</li>
<li><p>Kubernetes, a set of supported <abbr title="Container Runtime Interface">CRI</abbr>
runtimes, <abbr title="Container Network Interface">CNI</abbr> and <a class="reference external" href="https://github.com/clearlinux/cloud-native-setup/tree/master/clr-k8s-examples">cloud-native-setup
scripts</a> are included in the <a class="reference external" href="https://github.com/clearlinux/clr-bundles/blob/master/bundles/cloud-native-basic">cloud-native-basic</a> bundle. Install the
cloud-native-basic bundle to get these components:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>swupd<span class="w"> </span>bundle-add<span class="w"> </span>cloud-native-basic
</pre></div>
</div>
</li>
</ol>
</section>
<section id="set-up-kubernetes-automatically">
<h2><a class="toc-backref" href="#id8" role="doc-backlink">Set up Kubernetes automatically</a><a class="headerlink" href="#set-up-kubernetes-automatically" title="Link to this heading"></a></h2>
<p>Clear Linux OS provides <a class="reference external" href="https://github.com/clearlinux/cloud-native-setup/tree/master/clr-k8s-examples">cloud-native-setup scripts</a> to automate system setup and
Kubernetes cluster initialization which allows you to get a cluster up and
running quickly.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>By default, the scripts will update Clear Linux OS to the latest version, set up the
system as a Kubernetes master-node with <strong>canal for container networking</strong>
and <strong>crio for container runtime</strong>, and taint the master node to allow
workloads to run on it. Kata is installed as an optional alternative
runtime. The script can be configured to use other CNI’s and CRI’s by
following the directions on the <a class="reference external" href="https://github.com/clearlinux/cloud-native-setup/blob/master/clr-k8s-examples/README.md">README</a>.</p>
<p>See <a class="reference internal" href="#what-is-a-container-network-interface-cni">What is a Container Network Interface (CNI)?</a> and <a class="reference internal" href="#what-is-a-container-runtime-interface-cri">What is a
Container Runtime Interface (CRI)?</a> for more information.</p>
</div>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>If network proxy settings are required for Internet connectivity, configure
them now because the scripts will propagate proxy configuration based on
the running configuration. It is especially important to set the
<strong class="command">no_proxy</strong> variable appropriately for Kubernetes.</p>
<p>The script will also modify the <code class="file docutils literal notranslate"><span class="pre">/etc/environment</span></code> and
<code class="file docutils literal notranslate"><span class="pre">/etc/profile.d/proxy.sh</span></code> files, if they exist, with the proxy
environment variables in the running shell when the script is executed.</p>
<p>See the <a class="reference internal" href="#setting-proxy-servers-for-kubernetes">Setting proxy servers for Kubernetes</a> section for details.</p>
</div>
<ol class="arabic">
<li><p>Run the <code class="file docutils literal notranslate"><span class="pre">system-setup.sh</span></code> script to configure the Clear Linux OS system
settings.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>/usr/share/clr-k8s-examples/setup_system.sh
</pre></div>
</div>
</li>
<li><p>Stop docker and containerd to avoid conflicting CRIs being detected. The
scripts use CRIO for the CRI.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span>stop<span class="w"> </span>docker
sudo<span class="w"> </span>systemctl<span class="w"> </span>stop<span class="w"> </span>containerd
</pre></div>
</div>
</li>
<li><p>Install git as it’s a dependency of the <code class="file docutils literal notranslate"><span class="pre">create_stack.sh</span></code>.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>swupd<span class="w"> </span>bundle-add<span class="w"> </span>git
</pre></div>
</div>
</li>
<li><p>Run the <code class="file docutils literal notranslate"><span class="pre">create_stack.sh</span></code> script to initialize the Kubernetes node
and setup a container network plugin.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>/usr/share/clr-k8s-examples/create_stack.sh<span class="w"> </span>minimal
</pre></div>
</div>
</li>
<li><p>Follow the output on the screen and continue onto the section on <a class="reference external" href="#use-your-cluster">using
your cluster</a>.</p></li>
</ol>
<section id="uninstalling">
<h3>Uninstalling<a class="headerlink" href="#uninstalling" title="Link to this heading"></a></h3>
<ol class="arabic">
<li><p>If you need to delete the Kubernetes cluster or want to start from scratch
run the <code class="file docutils literal notranslate"><span class="pre">reset_stack.sh</span></code> script.</p>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<p>This will stop components in the stack including Kubernetes, all CNI and
CRIs <strong>and will delete</strong> all containers and networks.</p>
</div>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>/usr/share/clr-k8s-examples/reset_stack.sh
</pre></div>
</div>
</li>
</ol>
</section>
</section>
<section id="set-up-kubernetes-manually">
<h2><a class="toc-backref" href="#id9" role="doc-backlink">Set up Kubernetes manually</a><a class="headerlink" href="#set-up-kubernetes-manually" title="Link to this heading"></a></h2>
<section id="configure-host-system">
<h3>Configure host system<a class="headerlink" href="#configure-host-system" title="Link to this heading"></a></h3>
<p>This tutorial uses the basic default Kubernetes configuration to get started.
You can customize your Kubernetes configuration according to your specific
deployment and security needs.</p>
<p>The Kubernetes administration tool, <strong class="command">kubeadm</strong>, performs some
“<a class="reference external" href="https://kubernetes.io/docs/reference/setup-tools/kubeadm/implementation-details/#preflight-checks">preflight checks</a>” when initializing and starting a cluster. The steps
below are necessary to ensure those preflight checks pass successfully.</p>
<ol class="arabic">
<li><p>Enable IP forwarding:</p>
<ul>
<li><p>Create the file <code class="file docutils literal notranslate"><span class="pre">/etc/sysctl.d/60-k8s.conf</span></code> to set the
<strong class="command">net.ipv4.ip_forward</strong> parameter</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>mkdir<span class="w"> </span>-p<span class="w"> </span>/etc/sysctl.d/
sudo<span class="w"> </span>tee<span class="w"> </span>/etc/sysctl.d/99-kubernetes-cri.conf<span class="w"> </span>&gt;<span class="w"> </span>/dev/null<span class="w"> </span><span class="s">&lt;&lt;EOF</span>
<span class="s">net.bridge.bridge-nf-call-iptables = 1</span>
<span class="s">net.ipv4.ip_forward = 1</span>
<span class="s">net.bridge.bridge-nf-call-ip6tables = 1</span>
<span class="s">EOF</span>
</pre></div>
</div>
</li>
<li><p>Apply the change:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>sysctl<span class="w"> </span>--system
</pre></div>
</div>
</li>
</ul>
</li>
<li><p>Disable swap:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span>mask<span class="w"> </span><span class="k">$(</span>sed<span class="w"> </span>-n<span class="w"> </span>-e<span class="w"> </span><span class="s1">&#39;s#^/var/\([0-9a-z]*\).*#var-\1.swap#p&#39;</span><span class="w"> </span>/proc/swaps<span class="k">)</span><span class="w"> </span><span class="m">2</span>&gt;/dev/null
sudo<span class="w"> </span>swapoff<span class="w"> </span>-a
</pre></div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Kubernetes is designed to work without swap. Performance degradation of other workloads can occur
with swap disabled on systems with constrained memory resources.</p>
</div>
</li>
<li><p>Add the the system’s hostname to the <code class="file docutils literal notranslate"><span class="pre">/etc/hosts</span></code> file. Kubernetes
will read this file to locate the master host.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nb">echo</span><span class="w"> </span><span class="s2">&quot;127.0.0.1 localhost `hostname`&quot;</span><span class="w"> </span><span class="p">|</span><span class="w"> </span>sudo<span class="w"> </span>tee<span class="w"> </span>--append<span class="w"> </span>/etc/hosts
</pre></div>
</div>
</li>
<li><p>Enable the kubelet agent service to start at boot automatically:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span><span class="nb">enable</span><span class="w"> </span>kubelet.service
</pre></div>
</div>
</li>
</ol>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>If network proxy settings are required for Internet connectivity, configure
them now because the scripts will propagate proxy configuration based on
the running configuration. It is especially important to set the
<strong class="command">no_proxy</strong> variable for Kubernetes. See the <a class="reference internal" href="#setting-proxy-servers-for-kubernetes">Setting proxy servers
for Kubernetes</a> section for details.</p>
</div>
</section>
</section>
<section id="initialize-the-master-node">
<h2><a class="toc-backref" href="#id10" role="doc-backlink">Initialize the master node</a><a class="headerlink" href="#initialize-the-master-node" title="Link to this heading"></a></h2>
<p>In Kubernetes, a master node is part of the <a class="reference external" href="https://kubernetes.io/docs/concepts/#kubernetes-control-plane">Kubernetes Control Plane</a>.</p>
<p>Initializing a new Kubernetes cluster involves crafting a <strong class="command">kubeadm
init</strong> command. Adding parameters to this command can control the fundamental
operating components of the cluster. This means it is important to understand
and choose network and runtime options before running a <strong class="command">kubeadm
init</strong> command.</p>
<section id="choose-a-pod-network-add-on">
<h3>Choose a pod network add-on<a class="headerlink" href="#choose-a-pod-network-add-on" title="Link to this heading"></a></h3>
<p>See <a class="reference internal" href="#what-is-a-container-network-interface-cni">What is a Container Network Interface (CNI)?</a> for information on what
pod network add-ons and CNIs.</p>
<p>It is important to decide which CNI will be used early because some pod
network add-ons require configuration during cluster initialization. Check
whether or not your add-on requires special flags when you initialize the
master control plane.</p>
<p>If your chosen network add-on requires appending to the <strong class="command">kubeadm
init</strong> command, make note of it before continuing. For example, if you choose
the <em>flannel</em> pod network add-on, then in later steps you must add the
following to the <strong class="command">kubeadm init</strong> command:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">--pod-network-cidr 10.244.0.0/16</span>
</pre></div>
</div>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>The version of CNI plugins installed needs to be compatible with the
version of Kubernetes that is installed otherwise the cluster may fail.
Check the Kubernetes version with <strong class="command">kubeadm version -o short</strong> and
refer to the documentation of the CNI plugins to obtain a compatible
version.</p>
</div>
</section>
<section id="choose-a-container-runtime">
<h3>Choose a container runtime<a class="headerlink" href="#choose-a-container-runtime" title="Link to this heading"></a></h3>
<p>See <a class="reference internal" href="#what-is-a-container-runtime-interface-cri">What is a Container Runtime Interface (CRI)?</a> for more information on
what a CRI is.</p>
<p>Clear Linux OS supports Kubernetes with the various runtimes
below with or without <a class="reference external" href="https://katacontainers.io/">Kata Containers</a>:</p>
<ul class="simple">
<li><p><a class="reference external" href="https://cri-o.io/">CRI+O</a></p></li>
<li><p><a class="reference external" href="https://containerd.io/">containerd</a></p></li>
<li><p><a class="reference external" href="https://www.docker.com/">Docker</a></p></li>
</ul>
<p>The container runtime that you choose will dictate the steps necessary to
initialize the master cluster with <strong class="command">kubeadm init</strong>.</p>
<section id="cri-o">
<h4>CRI+O<a class="headerlink" href="#cri-o" title="Link to this heading"></a></h4>
<p>For information on CRI+O as a Kubernetes CRI, see <a class="reference internal" href="#what-is-cri-o">What is
CRI+O?</a>. To use CRI+O as the Kubernetes CRI:</p>
<ol class="arabic">
<li><p>Start the CRI-O service and enable it to run at boot automatically:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span><span class="nb">enable</span><span class="w"> </span>--now<span class="w"> </span>crio.service
</pre></div>
</div>
<p>When the crio service starts for the first time, it will create a
configuration file for crio at <code class="file docutils literal notranslate"><span class="pre">/etc/crio/crio.conf</span></code>.</p>
</li>
<li><p>Run the kubeadm command to initialize the master node with the
<strong class="command">--cri-socket</strong> parameter:</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>You may need to add additional parameters to the command below,
depending the pod network addon in use.</p>
<p>In this example, the <strong class="command">--pod-network-cidr 10.244.0.0/16</strong>
parameter is to use <em>flannel</em> as the pod networking. See <a class="reference internal" href="#choose-a-pod-network-add-on">Choose a pod
network add-on</a> for more information.</p>
</div>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>kubeadm<span class="w"> </span>init<span class="w"> </span><span class="se">\</span>
--cri-socket<span class="o">=</span>unix:///run/crio/crio.sock<span class="w"> </span><span class="se">\</span>
--pod-network-cidr<span class="w"> </span><span class="m">10</span>.244.0.0/16
</pre></div>
</div>
</li>
<li><p>(Optional) By default, CRI+O will use runc as the default
runtime. CRI+O can optionally provide Kata Containers as a runtime. See
the <a class="reference internal" href="#add-the-kata-runtime-to-kubernetes">Add the Kata runtime to Kubernetes</a> section for details.</p>
<p>With CRI+O, the <a class="reference external" href="https://katacontainers.io/">Kata Containers</a> can be set as the runtime with a
per-pod <em>RuntimeClass</em> annotation.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>If you are using CRI-O + Kata Containers as the runtime and choose the
<em>flannel</em> for pod networking (see <a class="reference internal" href="#choose-a-pod-network-add-on">Choose a pod network add-on</a>), the
<code class="file docutils literal notranslate"><span class="pre">/etc/crio/crio.conf</span></code> file needs to include the value below. On
Clear Linux OS this is done automatically.</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">[crio.runtime]</span>
<span class="go">manage_network_ns_lifecycle = true</span>
</pre></div>
</div>
</div>
</li>
<li><p>Once the cluster initialization is complete, continue reading about how to
<a class="reference internal" href="#use-your-cluster">Use your cluster</a>.</p></li>
</ol>
</section>
<section id="containerd">
<h4>containerd<a class="headerlink" href="#containerd" title="Link to this heading"></a></h4>
<p>For information on containerd as as Kubernetes CRI, see <a class="reference internal" href="#what-is-containerd">What is
containerd?</a>. To use containerd as the Kubernetes CRI:</p>
<ol class="arabic">
<li><p>Start the containerd service and enable it to run at boot automatically:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span><span class="nb">enable</span><span class="w"> </span>--now<span class="w"> </span>containerd.service
</pre></div>
</div>
</li>
<li><p>Configure kubelet to use containerd. and reload the service.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>mkdir<span class="w"> </span>-p<span class="w"> </span>/etc/systemd/system/kubelet.service.d/
cat<span class="w"> </span><span class="s">&lt;&lt; EOF | sudo tee /etc/systemd/system/kubelet.service.d/0-containerd.conf</span>
<span class="s">[Service]</span>
<span class="s">Environment=&quot;KUBELET_EXTRA_ARGS=--container-runtime=remote --runtime-request-timeout=15m --container-runtime-endpoint=unix:///run/containerd/containerd.sock&quot;</span>
<span class="s">EOF</span>
</pre></div>
</div>
</li>
<li><p>Configure kubelet to use systemd as the cgroup driver. and reload the
service.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>mkdir<span class="w"> </span>-p<span class="w"> </span>/etc/systemd/system/kubelet.service.d/
cat<span class="w"> </span><span class="s">&lt;&lt; EOF | sudo tee /etc/systemd/system/kubelet.service.d/10-cgroup-driver.conf</span>
<span class="s">[Service]</span>
<span class="s">Environment=&quot;KUBELET_EXTRA_ARGS=--cgroup-driver=systemd&quot;</span>
<span class="s">EOF</span>
</pre></div>
</div>
</li>
<li><p>Reload the systemd manager configuration.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span>daemon-reload
</pre></div>
</div>
</li>
<li><p>Run the kubeadm command to initialize the master node with the
<strong class="command">--cri-socket</strong> parameter:</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>You may need to add additional parameters to the command below,
depending the pod network addon in use.</p>
<p>In this example, the <strong class="command">--pod-network-cidr 10.244.0.0/16</strong>
parameter is to use <em>flannel</em> as the pod networking. See <a class="reference internal" href="#choose-a-pod-network-add-on">Choose a pod
network add-on</a> for more information.</p>
</div>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>kubeadm<span class="w"> </span>init<span class="w"> </span><span class="se">\</span>
--cri-socket<span class="o">=</span>/run/containerd/containerd.sock
--pod-network-cidr<span class="w"> </span><span class="m">10</span>.244.0.0/16
</pre></div>
</div>
</li>
<li><p>(Optional) By default, containerd will use runc as the default
runtime. containerd can optionally provide Kata Containers as a runtime.
See the <a class="reference internal" href="#add-the-kata-runtime-to-kubernetes">Add the Kata runtime to Kubernetes</a> section for details.</p>
<p>With containerd, the <a class="reference external" href="https://katacontainers.io/">Kata Containers</a> can be set as the runtime with a
per-pod <em>RuntimeClass</em> annotation.</p>
</li>
<li><p>Once the cluster initialization is complete, continue reading about how to
<a class="reference internal" href="#use-your-cluster">Use your cluster</a>.</p></li>
</ol>
</section>
<section id="docker">
<h4>Docker<a class="headerlink" href="#docker" title="Link to this heading"></a></h4>
<p>For information on Docker, see <a class="reference internal" href="#what-is-docker">What is Docker?</a>. To use Docker as the
Kubernetes container runtime:</p>
<ol class="arabic">
<li><p>Make sure Docker is installed:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>swupd<span class="w"> </span>bundle-add<span class="w"> </span>containers-basic
</pre></div>
</div>
</li>
<li><p>Start the Docker service and enable it to start automatically at boot:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">sudo</span> <span class="n">systemctl</span> <span class="n">enable</span> <span class="o">--</span><span class="n">now</span> <span class="n">docker</span><span class="o">.</span><span class="n">service</span>
</pre></div>
</div>
</li>
<li><p>Configure kubelet to use the Clear Linux OS directory for cni-plugins and reload the
service.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>mkdir<span class="w"> </span>-p<span class="w"> </span>/etc/systemd/system/kubelet.service.d/
cat<span class="w"> </span><span class="s">&lt;&lt; EOF | sudo tee /etc/systemd/system/kubelet.service.d/0-cni.conf</span>
<span class="s">[Service]</span>
<span class="s">Environment=&quot;KUBELET_EXTRA_ARGS=--cni-bin-dir=/usr/libexec/cni&quot;</span>
<span class="s">EOF</span>
</pre></div>
</div>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span>daemon-reload
</pre></div>
</div>
</li>
<li><p>Run the kubeadm command to initialize the master node:</p>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p>You may need to add additional parameters to the command below,
depending the pod network addon in use.</p>
<p>In this example, the <strong class="command">--pod-network-cidr 10.244.0.0/16</strong>
parameter is to use <em>flannel</em> as the pod networking. See <a class="reference internal" href="#choose-a-pod-network-add-on">Choose a pod
network add-on</a> for more information.</p>
</div>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>kubeadm<span class="w"> </span>init<span class="w"> </span><span class="se">\</span>
--pod-network-cidr<span class="w"> </span><span class="m">10</span>.244.0.0/16
</pre></div>
</div>
</li>
<li><p>Once the cluster initialization is complete, continue reading about how to
<a class="reference internal" href="#use-your-cluster">Use your cluster</a>.</p></li>
</ol>
</section>
<section id="add-the-kata-runtime-to-kubernetes">
<h4>Add the Kata runtime to Kubernetes<a class="headerlink" href="#add-the-kata-runtime-to-kubernetes" title="Link to this heading"></a></h4>
<p>For information on Kata as a container runtime, see <a class="reference internal" href="#what-is-kata-containers">What is Kata Containers*?</a>.
Using Kata Containers is optional.</p>
<p>You can use <em>kata-deploy</em> to install all the necessary parts of Kata
Containers after you have a Kubernetes cluster running with one of the CRI’s
using the default runc runtime. Follow the steps in the Kubernetes quick start
section of the <a class="reference external" href="https://github.com/kata-containers/packaging/tree/master/kata-deploy#kubernetes-quick-start">kata-containers GitHub README</a>
to install Kata.</p>
</section>
</section>
</section>
<section id="use-your-cluster">
<h2><a class="toc-backref" href="#id11" role="doc-backlink">Use your cluster</a><a class="headerlink" href="#use-your-cluster" title="Link to this heading"></a></h2>
<p>Once your master control plane is successfully initialized, follow the
instructions presented about how to use your cluster and its <em>IP</em>, <em>token</em>,
and <em>hash</em> values are displayed. It is important that you record this
information because it is required to join additional nodes to the cluster.</p>
<p>A successful initialization looks like this:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">Your Kubernetes control-plane has initialized successfully!</span>
<span class="go">To start using your cluster, you need to run the following as a regular user:</span>
<span class="go">mkdir -p $HOME/.kube</span>
<span class="go">sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config</span>
<span class="go">sudo chown $(id -u):$(id -g) $HOME/.kube/config</span>
<span class="go">...</span>
<span class="go">You can now join any number of machines by running the following on each node</span>
<span class="go">as root:</span>
<span class="go">kubeadm join &lt;control-plane-host&gt;:&lt;control-plane-port&gt; --token &lt;token&gt; --discovery-token-ca-cert-hash sha256:&lt;hash&gt;</span>
</pre></div>
</div>
<p>With the first node of the cluster setup, you can continue expanding the
cluster with additional nodes and start deploying containerized applications.
For further information on using Kubernetes, see <a class="reference internal" href="#related-topics">Related topics</a>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>By default, the master node does not run any pods for security reasons. To
setup a single-node cluster and allow the master node to also run pods, the
master node will need to be untained. See the Kubernetes documentation on
<a class="reference external" href="https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/#control-plane-node-isolation">control plane node isolation</a>.</p>
</div>
</section>
<section id="troubleshooting">
<h2><a class="toc-backref" href="#id12" role="doc-backlink">Troubleshooting</a><a class="headerlink" href="#troubleshooting" title="Link to this heading"></a></h2>
<section id="package-configuration-customization">
<h3>Package configuration customization<a class="headerlink" href="#package-configuration-customization" title="Link to this heading"></a></h3>
<p>Clear Linux OS is a stateless system that looks for user-defined package configuration
files in the <code class="file docutils literal notranslate"><span class="pre">/etc/&lt;package-name&gt;</span></code> directory to be used as default. If
user-defined files are not found, Clear Linux OS uses the distribution-provided
configuration files for each package.</p>
<p>If you customize any of the default package configuration files, you <strong>must</strong>
store the customized files in the <code class="file docutils literal notranslate"><span class="pre">/etc/</span></code> directory. If you edit any of
the distribution-provided default files, your changes will be lost in the next
system update as the default files will be overwritten with the updated files.</p>
<p>Learn more about <a class="reference internal" href="../guides/clear/stateless.html#stateless"><span class="std std-ref">Stateless</span></a> in Clear Linux OS.</p>
</section>
<section id="logs">
<h3>Logs<a class="headerlink" href="#logs" title="Link to this heading"></a></h3>
<ul class="simple">
<li><p>Check the kubelet service logs <strong class="command">sudo journalctl -u kubelet</strong></p></li>
</ul>
</section>
<section id="setting-proxy-servers-for-kubernetes">
<h3>Setting proxy servers for Kubernetes<a class="headerlink" href="#setting-proxy-servers-for-kubernetes" title="Link to this heading"></a></h3>
<p>If you receive any of the messages below, check outbound Internet access. You
may be behind a proxy server.</p>
<blockquote>
<div><ul>
<li><p>Images cannot be pulled.</p></li>
<li><p>Connection refused error.</p></li>
<li><p>Connection timed-out or Access Refused errors.</p></li>
<li><p>The warnings when <strong class="command">kubeadm init</strong> is run.</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">[WARNING HTTPProxy]: Connection to &quot;https://&lt;HOST-IP&gt;&quot; uses proxy &quot;&lt;PROXY-SERVER&gt;&quot;. If that is not intended, adjust your proxy settings</span>
<span class="go">[WARNING HTTPProxyCIDR]: connection to &quot;10.96.0.0/12&quot; uses proxy &quot;&lt;PROXY-SERVER&gt;&quot;. This may lead to malfunctional cluster setup. Make sure that Pod and Services IP ranges specified correctly as exceptions in proxy configuration</span>
<span class="go">[WARNING HTTPProxyCIDR]: connection to &quot;10.244.0.0/16&quot; uses proxy &quot;&lt;PROXY-SERVER&gt;&quot;. This may lead to malfunctional cluster setup. Make sure that Pod and Services IP ranges specified correctly as exceptions in proxy configuration</span>
</pre></div>
</div>
</li>
</ul>
</div></blockquote>
<p>If you use an outbound proxy server, you must configure proxy settings
appropriately for all components in the stack including <strong class="command">kubectl</strong> and
container runtime services.</p>
<p>Configure the <a class="reference internal" href="../guides/network/proxy.html#proxy"><span class="std std-ref">proxy settings</span></a>, using the standard <em>HTTP_PROXY</em>,
<em>HTTPS_PROXY</em>, and <em>NO_PROXY</em> environment variables. The <em>NO_PROXY</em> values are
especially important for Kubernetes to ensure private IP traffic does not try
to go out the proxy.</p>
<ol class="arabic">
<li><p>Set your environment proxy variables. Ensure that your local IP address is
<strong>explicitly included</strong> in the environment variable <em>NO_PROXY</em>. Setting
<em>localhost</em> is not sufficient!</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nb">export</span><span class="w"> </span><span class="nv">http_proxy</span><span class="o">=</span>http://proxy.example.com:80
<span class="nb">export</span><span class="w"> </span><span class="nv">https_proxy</span><span class="o">=</span>http://proxy.example.com:443
<span class="nb">export</span><span class="w"> </span><span class="nv">no_proxy</span><span class="o">=</span>.svc,10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,<span class="sb">`</span>hostname<span class="sb">`</span>,localhost
</pre></div>
</div>
<div class="admonition important">
<p class="admonition-title">Important</p>
<p><strong class="command">kubeadm</strong> commands specifically use these shell variables for proxy
configuration. Ensure they are set your running terminal before running
<strong class="command">kubeadm</strong> commands.</p>
</div>
</li>
<li><p>Run the following command to add systemd drop-in configurations for each
service to include proxy settings:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="nv">services</span><span class="o">=(</span>kubelet<span class="w"> </span>docker<span class="w"> </span>crio<span class="w"> </span>containerd<span class="o">)</span>
<span class="k">for</span><span class="w"> </span>s<span class="w"> </span><span class="k">in</span><span class="w"> </span><span class="s2">&quot;</span><span class="si">${</span><span class="nv">services</span><span class="p">[@]</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">;</span><span class="w"> </span><span class="k">do</span>
sudo<span class="w"> </span>mkdir<span class="w"> </span>-p<span class="w"> </span><span class="s2">&quot;/etc/systemd/system/</span><span class="si">${</span><span class="nv">s</span><span class="si">}</span><span class="s2">.service.d/&quot;</span>
cat<span class="w"> </span><span class="s">&lt;&lt; EOF | sudo tee &quot;/etc/systemd/system/${s}.service.d/proxy.conf&quot;</span>
<span class="s">[Service]</span>
<span class="s">Environment=&quot;HTTP_PROXY=${http_proxy}&quot;</span>
<span class="s">Environment=&quot;HTTPS_PROXY=${https_proxy}&quot;</span>
<span class="s">Environment=&quot;SOCKS_PROXY=${socks_proxy}&quot;</span>
<span class="s">Environment=&quot;NO_PROXY=${no_proxy}&quot;</span>
<span class="s">EOF</span>
<span class="k">done</span>
</pre></div>
</div>
</li>
<li><p>Reload the systemd manager configuration.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>systemctl<span class="w"> </span>daemon-reload
</pre></div>
</div>
</li>
</ol>
<p>If you had a previously failed initialization due to a proxy issue, restart
the process with the <strong class="command">kubeadm reset</strong> command.</p>
</section>
<section id="dns-issues">
<h3>DNS issues<a class="headerlink" href="#dns-issues" title="Link to this heading"></a></h3>
<ul>
<li><p>&lt;HOSTNAME&gt; not found in &lt;IP&gt; message.</p>
<blockquote>
<div><p>Your DNS server may not be appropriately configured. Try adding an entry
to the <code class="file docutils literal notranslate"><span class="pre">/etc/hosts</span></code> file with your host’s IP and Name.</p>
<p>Use the commands <strong class="command">hostname</strong> and <strong class="command">hostname -I</strong> to
retrieve them.</p>
<p>For example:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span><span class="m">10</span>.200.50.20<span class="w"> </span>myhost
</pre></div>
</div>
</div></blockquote>
</li>
<li><p>coredns pods are stuck in container creating state and logs show entries
similar to one of the following:</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go"> Warning FailedCreatePodSandBox 5m7s kubelet, kata3 Failed to create pod sandbox: rpc error: code = Unknown desc = failed to get network JSON for pod sandbox k8s_coredns-&lt;ID&gt;&gt;-5gpj2_kube-system_&lt;UUID&gt;): cannot convert version [&quot;&quot; &quot;0.1.0&quot; &quot;0.2.0&quot;] to 0.4.0</span>
<span class="go">In this case the :file:`/etc/cni/net.d/10-flannel.conf` or another CNI file</span>
<span class="go">is using an incompatible version. Delete the file and restart the stack.</span>
</pre></div>
</div>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">Warning FailedCreatePodSandBox 117s (x197 over 45m) kubelet, kata3 (combined from similar events): Failed to create pod sandbox: rpc error: code = Unknown desc = failed to create pod network sandbox k8s_coredns-&lt;ID&gt;&gt;-npsm5_kube-system_&lt;UUID&gt;: error getting ClusterInformation: Get https://[10.96.0.1]:443/apis/crd.projectcalico.org/v1/clusterinformations/default: x509: certificate signed by unknown authority (possibly because of &quot;crypto/rsa: verification error&quot; while trying to verify candidate authority certificate &quot;kubernetes&quot;)</span>
</pre></div>
</div>
<p>In this case, there may be multiple CNI configuration files in the
<code class="file docutils literal notranslate"><span class="pre">/etc/cni/net.d</span></code> folder. Delete all the files in this directory and
restart the stack.</p>
<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="go">Warning FailedScheduling 55s (x3 over 2m12s) default-scheduler 0/1</span>
<span class="go">nodes are available: 1 node(s) had taints that the pod didn&#39;t tolerate.</span>
</pre></div>
</div>
<p>In this case, there may be multiple CNI configuration files in the
<code class="file docutils literal notranslate"><span class="pre">/etc/cni/net.d</span></code> folder. Delete all the files in this directory, apply
a CNI plugin, and restart the stack.</p>
</li>
</ul>
</section>
</section>
<section id="reference">
<h2><a class="toc-backref" href="#id13" role="doc-backlink">Reference</a><a class="headerlink" href="#reference" title="Link to this heading"></a></h2>
<section id="what-is-kubernetes">
<h3>What is Kubernetes?<a class="headerlink" href="#what-is-kubernetes" title="Link to this heading"></a></h3>
<p>Kubernetes (K8s) is an open source system for automating deployment, scaling,
and management of containerized applications. It groups containers that make
up an application into logical units for easy management and discovery.</p>
<p>Kubernetes supports using a variety of <a class="reference external" href="https://kubernetes.io/docs/setup/production-environment/container-runtimes/">container runtimes</a>.</p>
</section>
<section id="what-is-a-container-network-interface-cni">
<h3>What is a Container Network Interface (CNI)?<a class="headerlink" href="#what-is-a-container-network-interface-cni" title="Link to this heading"></a></h3>
<p>In Kubernetes, a <a class="reference external" href="https://kubernetes.io/docs/concepts/workloads/pods/pod/">pod</a> is a group of one
or more containers and is the smallest deployable unit of computing in a
Kubernetes cluster. Pods have shared storage/network internally but
communication between pods requires additional configuration. If you want your
pods to be able to communicate with each other you must choose and install a
<a class="reference external" href="https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/#pod-network">pod network add-on</a>.</p>
<p>Some pod network add-ons enable advanced functionality with physical networks
or cloud provider networks.</p>
</section>
<section id="what-is-a-container-runtime-interface-cri">
<h3>What is a Container Runtime Interface (CRI)?<a class="headerlink" href="#what-is-a-container-runtime-interface-cri" title="Link to this heading"></a></h3>
<p>Container runtimes are the underlying fabric that pod workloads execute inside
of. Different container runtimes offer different balances between features,
performance, and security.</p>
<p>Kubernetes allows integration various container runtimes via a container
runtime interface (CRI).</p>
<section id="what-is-cri-o">
<h4>What is CRI+O?<a class="headerlink" href="#what-is-cri-o" title="Link to this heading"></a></h4>
<p><a class="reference external" href="https://cri-o.io/">CRI+O</a> is a lightweight alternative to using Docker as
the runtime for kubernetes. It allows Kubernetes to use any OCI-compliant
runtime as the container runtime for running pods, such as runc and
Kata Containers as the container runtimes.</p>
<p>CRI+O allows setting a different runtime per-pod.</p>
</section>
<section id="what-is-containerd">
<h4>What is containerd?<a class="headerlink" href="#what-is-containerd" title="Link to this heading"></a></h4>
<p><a class="reference external" href="https://containerd.io/">containerd</a> is the runtime that the Docker engine
is built on top of.</p>
<p>Kubernetes can use containerd directly instead of going through the Docker
engine for increased robustness and performance. See the <a class="reference external" href="https://kubernetes.io/blog/2018/05/24/kubernetes-containerd-integration-goes-ga/">blog post on
kubernetes containerd integration</a>
for more details.</p>
<p>containerd allows setting a different runtime per-pod.</p>
</section>
<section id="what-is-docker">
<h4>What is Docker?<a class="headerlink" href="#what-is-docker" title="Link to this heading"></a></h4>
<p><a class="reference external" href="https://www.docker.com/">Docker</a> is an engine for running software packaged
as functionally complete units, called containers, using the same operating
system kernel.</p>
<p>The default built-in runtime provided by Kubernetes is using the system Docker
installation via Dockershim and as a result is one of the simplest to use. One
limitation of using Dockershim is that all pods on the Kubernetes node will
inherit and use the default runtime that Docker is set to use. To be able to
specify a container runtime per-Kerbernetes service, use CRI+O or containerd.</p>
</section>
</section>
<section id="what-is-kata-containers">
<h3>What is Kata Containers*?<a class="headerlink" href="#what-is-kata-containers" title="Link to this heading"></a></h3>
<p><a class="reference external" href="https://katacontainers.io/">Kata Containers</a> is an alternative OCI compatible runtime that secures
container workloads in a lightweight virtual machine. It provides stronger
workloads isolation using hardware virtualization technology as a second layer
of defense for untrusted workloads or multi-tenant scenarios.</p>
<p>The Kata Containers (kata-runtime) adheres to <abbr title="Open Container Initiative*">OCI</abbr> guidelines and works seamlessly with Kubernetes through Docker,
containerd, or CRI+O.</p>
</section>
<section id="related-topics">
<h3>Related topics<a class="headerlink" href="#related-topics" title="Link to this heading"></a></h3>
<ul class="simple">
<li><p><a class="reference external" href="https://kubernetes.io/docs/user-journeys/users/application-developer/foundational/#section-3">Understanding basic Kubernetes architecture</a></p></li>
<li><p>Installing a <a class="reference external" href="https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/#pod-network">pod network add-on</a></p></li>
<li><p><a class="reference external" href="https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/#join-nodes">Joining your nodes</a></p></li>
<li><p><a class="reference external" href="https://kubernetes.io/docs/user-journeys/users/application-developer/foundational/#section-2">Deploying an application to your cluster</a></p></li>
<li><p>See our document on <a class="reference internal" href="kubernetes-bp.html#kubernetes-bp"><span class="std std-ref">Kubernetes best practices</span></a></p></li>
</ul>
</section>
</section>
</section>
<div class="clearer"></div>
</div>
</div>
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<div>
<h3><a href="../index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Kubernetes*</a><ul>
<li><a class="reference internal" href="#background">Background</a></li>
<li><a class="reference internal" href="#prerequisites">Prerequisites</a></li>
<li><a class="reference internal" href="#set-up-kubernetes-automatically">Set up Kubernetes automatically</a><ul>
<li><a class="reference internal" href="#uninstalling">Uninstalling</a></li>
</ul>
</li>
<li><a class="reference internal" href="#set-up-kubernetes-manually">Set up Kubernetes manually</a><ul>
<li><a class="reference internal" href="#configure-host-system">Configure host system</a></li>
</ul>
</li>
<li><a class="reference internal" href="#initialize-the-master-node">Initialize the master node</a><ul>
<li><a class="reference internal" href="#choose-a-pod-network-add-on">Choose a pod network add-on</a></li>
<li><a class="reference internal" href="#choose-a-container-runtime">Choose a container runtime</a><ul>
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<li><a class="reference internal" href="#setting-proxy-servers-for-kubernetes">Setting proxy servers for Kubernetes</a></li>
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<li><a class="reference internal" href="#reference">Reference</a><ul>
<li><a class="reference internal" href="#what-is-kubernetes">What is Kubernetes?</a></li>
<li><a class="reference internal" href="#what-is-a-container-network-interface-cni">What is a Container Network Interface (CNI)?</a></li>
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<li><a class="reference internal" href="#what-is-containerd">What is containerd?</a></li>
<li><a class="reference internal" href="#what-is-docker">What is Docker?</a></li>
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<li><a class="reference internal" href="#what-is-kata-containers">What is Kata Containers*?</a></li>
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