Kubernetes on sysarcher/@ich_codehttps://sysarcher.github.io/categories/kubernetes/Recent content in Kubernetes on sysarcher/@ich_codeHugoen-usMon, 22 Oct 2018 21:22:37 +0200Kubernetes Pod Networks and Pluginshttps://sysarcher.github.io/posts/k8s-pod-networks/Mon, 22 Oct 2018 21:22:37 +0200https://sysarcher.github.io/posts/k8s-pod-networks/<h3 id="pod-networks">Pod Networks</h3> <p>It is natural that to get your first <code>k8s</code> cluster running you&rsquo;d want to remove the taint from the master node and use it as the cluster (i.e. a single-node cluster). The first thing that a person would do is not set the <a href="https://kubernetes.io/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/#installation">kubelet network plugin (&ndash;network-plugin=cni)</a>. It&rsquo;s certainly what I did wrong.</p> <p>The problem is you don&rsquo;t see the problem until later because the orchestrator will use docker&rsquo;s default networking which would quickly fail in a more-than-one node cluster. So, it&rsquo;s best practice to immediately apply a pod network!!</p>Pod Networks

It is natural that to get your first k8s cluster running you’d want to remove the taint from the master node and use it as the cluster (i.e. a single-node cluster). The first thing that a person would do is not set the kubelet network plugin (–network-plugin=cni). It’s certainly what I did wrong.

The problem is you don’t see the problem until later because the orchestrator will use docker’s default networking which would quickly fail in a more-than-one node cluster. So, it’s best practice to immediately apply a pod network!!

Device Sharing

What if you want to orchestrate the usage of resources (like GPU, audio, crypto) using Kubernetes? Its best practice to create a device plugin. NVIDIA has a k8s-device-plugin for it’s GPUs. If this plugin isn’t used, you basically end up having to install NVIDIA drivers inside the docker container and hope the host’s version of the driver is exactly the same and share the devices with the container.

This is more elegant. Do it!

]]>runc and Friendshttps://sysarcher.github.io/posts/runc-and-friends/Sat, 20 Oct 2018 21:22:37 +0200https://sysarcher.github.io/posts/runc-and-friends/<p>Had to dig a bit into Kubernetes&rsquo; friends recently. Here&rsquo;s a TL;DR of what&rsquo;s missing from the internet today:</p> <ul> <li><code>runc</code> is the <strong>CLI tool</strong> for running containers (create/run/delete/<del>manage</del>) <ul> <li><code>docker</code> uses <code>runc</code> as its runtime.</li> <li>Kubernetes uses <code>runc</code> as its runtime through <code>cri-o</code> (those &ldquo;unsupported Docker version detected&rdquo; errors you&rsquo;ve probably seen.. yeah!) There&rsquo;s no guarantee that <code>runc</code> will remain <code>cri-o</code> compatible.</li> </ul> </li> <li><code>cri-o</code> is an interface for container runtimes. Any compatible runtime can be used. <code>runc</code> is one of those others being <code>rkt</code> (never tested it), Kata containers and I guess many more.</li> <li><code>containerd</code> - runtime manager created by docker and later contributed to CNCF. It&rsquo;s the daemon that&rsquo;s running in the background doing your bidding that you pass through <code>runc</code>.</li> </ul>Had to dig a bit into Kubernetes’ friends recently. Here’s a TL;DR of what’s missing from the internet today:

  • runc is the CLI tool for running containers (create/run/delete/manage)
    • docker uses runc as its runtime.
    • Kubernetes uses runc as its runtime through cri-o (those “unsupported Docker version detected” errors you’ve probably seen.. yeah!) There’s no guarantee that runc will remain cri-o compatible.
  • cri-o is an interface for container runtimes. Any compatible runtime can be used. runc is one of those others being rkt (never tested it), Kata containers and I guess many more.
  • containerd - runtime manager created by docker and later contributed to CNCF. It’s the daemon that’s running in the background doing your bidding that you pass through runc.
]]>