chore: improved readibility

knowledge base/kubernetes/drain nodes.md

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+# Drain nodes in K8S clusters
+
+## Table of contents <!-- omit in toc -->
+
+1. [TL;DR](#tldr)
+1. [Further readings](#further-readings)
+1. [Sources](#sources)
+
+## TL;DR
+
+1. **Cordon** the Nodes.<br/>
+   This marks each Node as _unschedulable_ and prevents new Pods to start on them.
+
+   ```sh
+   $ kubectl cordon 'kworker-rj2'
+   node/kworker-rj2 cordoned
+   ```
+
+1. **Drain** the nodes.<br/>
+   This _evicts_ Pods already running on the Nodes.
+
+   ```sh
+   $ kubectl drain 'kworker-rj2' --grace-period=300 --ignore-daemonsets=true
+   node/kworker-rj2 already cordoned
+   WARNING: ignoring DaemonSet-managed Pods: kube-system/calico-node-fl8dl, kube-system/kube-proxy-95vdf
+   evicting pod default/my-dep-557548758d-d2pmd
+   pod/my-dep-557548758d-d2pmd evicted
+   node/kworker-rj2 evicted
+   ```
+
+1. Do to the Nodes what you need to do.
+1. **Uncordon** the Nodes.
+   This makes them available for scheduling again.
+
+   ```sh
+   $ kubectl uncordon 'kworker-rj2'
+   node/kworker-rj2 uncordoned
+   ```
+
+## Further readings
+
+- [Kubernetes]
+- [`kubectl`][kubectl]
+
+## Sources
+
+All the references in the [further readings] section, plus the following:
+
+- [How to drain a node in Kubernetes]
+
+<!--
+  References
+  -->
+
+<!-- In-article sections -->
+[further readings]: #further-readings
+
+<!-- Knowledge base -->
+[kubectl]: kubectl.md
+[kubernetes]: README.md
+
+<!-- Others -->
+[how to drain a node in kubernetes]: https://linuxhandbook.com/kubectl-drain-node/