Book Image

kubectl: Command-Line Kubernetes in a Nutshell

By : Rimantas Mocevicius
Book Image

kubectl: Command-Line Kubernetes in a Nutshell

By: Rimantas Mocevicius

Overview of this book

The kubectl command line tool lets you control Kubernetes clusters to manage nodes in the cluster and perform all types of Kubernetes operations. This introductory guide will get you up to speed with kubectl in no time. The book is divided into four parts, touching base on the installation and providing a general overview of kubectl in the first part. The second part introduces you to managing Kubernetes clusters and working with nodes. In the third part, you’ll be taken through the different ways in which you can manage Kubernetes applications, covering how to create, update, delete, view, and debug applications. The last part of the book focuses on various Kubernetes plugins and commands. You’ll get to grips with using Kustomize and discover Helm, a Kubernetes package manager. In addition to this, you’ll explore how you can use equivalent Docker commands in kubectl. By the end of this book, you’ll have learned how to install and update an application on Kubernetes, view its logs, and inspect clusters effectively.
Table of Contents (16 chapters)
Section 1: Getting Started with kubectl
Section 2: Kubernetes Cluster and Node Management
Section 3: Application Management
Section 4: Extending kubectl

Creating a basic plugin

In this section, let's create a simple plugin called toppods to show Kubernetes cluster nodes. It is just a very simple example of how to create the plugin:

  1. We are going to create a simple bash-based plugin named kubectl-toppods:
    $ cat kubectl-toppods
    kubectl top pods
  2. Let's copy the kubectl-toppods file to the ~/bin path:
    $ cp kubectl-toppods ~/bin
  3. Make sure it is executable:
    $ chmod +x ~/bin/ kubectl-toppods
  4. Now let's try to run it:
    $ kubectl toppods
    NAME                        CPU(cores)   MEMORY(bytes)
    postgresql-57578b68d9-6rpt8 1m           22Mi

Nice! You can see that the plugin is working, and it is not very difficult to create a kubectl plugin.