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kubectl: Command-Line Kubernetes in a Nutshell

Chapter 1: Introducing and Installing kubectl

Kubernetes is an open source container orchestration system for managing containerized applications across multiple hosts in a cluster.

Kubernetes provides mechanisms for application deployment, scheduling, updating, maintenance, and scaling. A key feature of Kubernetes is that it actively manages containers to ensure that the state of the cluster always matches the user's expectations.

Kubernetes enables you to respond quickly to customer demand by scaling or rolling out new features. It also allows you to make full use of your hardware.

Kubernetes is the following:

Lean: Lightweight, simple, and accessible
Portable: Public, private, hybrid, and multi-cloud
Extensible: Modular, pluggable, hookable, composable, and toolable
Self-healing: Auto-placement, auto-restart, and auto-replication

Kubernetes builds on a decade and a half of experience at Google running production workloads at scale, combined with best-of-breed ideas and best practices from the community:

Figure 1.1 – A 10,000-foot view of Kubernetes' architecture

One of the ways to manage Kubernetes clusters is kubectl—Kubernetes' command-line tool for management, it is a tool for accessing a Kubernetes cluster that allows you to run different commands against Kubernetes clusters to deploy apps, manage nodes, troubleshoot deployments, and more.

In this chapter, we're going to cover the following main topics:

Introducing kubectl
Installing kubectl
kubectl commands

kubectl commands

To get a list of supported kubectl commands, run this:

$ kubectl --help

kubectl commands are grouped by category. Let's look at each category.

Basic commands

The following are basic kubectl commands:

create: Create a resource from a file or from stdin; for example, create a Kubernetes deployment from the file.
expose: Take a service, deployment, or pod and expose it as a new Kubernetes Service.
run: Run a particular image on the cluster.
set: Set specific features on objects—for example, set environment variables, update a Docker image in a pod template, and so on.
explain: Get the documentation of resources—for example, the documentation on deployments.
get: Display one or many resources. For example, you can get a list of running pods or the YAML output of a pod.
edit: Edit a resource—for example, edit a deployment.
delete: Delete resources by filenames, stdin, resources, and names, or by resources and label selectors.

Deploy commands

The following are kubectl deploy commands:

rollout: Manage the rollout of a resource.
scale: Set a new size for a deployment, ReplicaSet, or StatefulSet.
autoscale: Auto-scale a deployment, ReplicaSet, or StatefulSet.

Cluster management commands

The following are the kubectl cluster management commands:

certificate: Modify certificate resources.
cluster-info: Display cluster information.
top: Display resource (CPU/memory/storage) usage.
cordon: Mark a node as unschedulable.
uncordon: Mark a node as schedulable.
drain: Drain a node in preparation for maintenance.
taint: Update the taints on one or more nodes.

Troubleshooting and debugging commands

The following are the kubectl troubleshooting and debugging commands:

describe: Show the details of a specific resource or group of resources.
logs: Print the logs for a container in a pod.
attach: Attach to a running container.
exec: Execute a command in a container.
port-forward: Forward one or more local ports to a pod.
proxy: Run a proxy to the Kubernetes API server.
cp: Copy files and directories to and from containers.
auth: Inspect authorization.

Advanced commands

The following are the kubectl advanced commands:

diff: Show difference of live version against a would-be applied version.
apply: Apply a configuration to a resource by filename or stdin.
patch: Update the field(s) of a resource using a strategic merge patch.
replace: Replace a resource by filename or stdin.
wait: Wait for a specific condition on one or many resources.
convert: Convert config files between different API versions.
kustomize: Build a kustomization target from a directory or a remote URL.

Settings commands

The following are the settings commands in kubectl:

label: Update the labels on a resource.
annotate: Update the annotations on a resource.

Other commands

The following are several other commands used in kubectl:

alpha: Commands for features in alpha.
api-resources: Print the supported API resources on the server.
api-versions: Print the supported API versions on the server, in the form of group/version.
config: Modify kube-config files.
plugin: Provide utilities for interacting with plugins.
version: Print the client and server version information.

As you can see from the lists, commands are divided into different groups. We are going to learn about most but not all of these commands in the coming chapters.

At the time of writing, the kubectl version is 1.18; with more recent versions, the commands might have changed.

Key benefits

Explore the Kubernetes command line for deploying applications, inspecting clusters, and viewing logs

Leverage kubectl for Kubernetes application management and container debugging

Apply your knowledge of Docker to learn kubectl equivalent commands for Docker subcommands

Description

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.

What you will learn

Get to grips with the basic kubectl commands

Delve into different cluster nodes and their resource usages

Understand the most essential features of kubectl

Discover how to patch Kubernetes deployments with Kustomize

Find out ways to extend kubectl tools with their own plugins

Explore how to use Helm as an advanced tool for deploying apps

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Walter Lee Dec 01, 2020

I highly recommend this new book by Rimantas Mocevicius. Finally a good book on the Swiss army knife, kubectl, for k8s with good examples. The first 6 chapters shows all about kubectl and how to do this and that with kubectl. Although we will often do declarative deployments. It is still important to know how to do things imperatively, e.g. k drain/cordon a problematic node, describe this and that k8s objects, k rollout undo/status/history, etc... It shows many real life kubectl on cloud examples with GCP GKE.I like Chapter 7 most because it shows how we can extend kubectl with plugins, e.g. how to use Krew to find and install plugins, then you can use "k really get all" plugin, k view-allocations, etc. It then teaches how to create your own simple plugin.Chapter 8 teaches Kustomize and how to use it to deploy with overlays.Chapter 9 is another favorite, Helm! Rimantas knows this very well because he is a co-author of Helm."Helm is the de facto Kubernetes package manager, and one of the best and easiest ways to install any kind of complex application on Kubernetes." (p. 93 of the book).He walks the readers step by step in Helm and how to use it to helm install, upgrade, rollback, template, lint, plugin, ... applications/deployments etc. For example, Rimantas shows us the proper way to change values of a helm chart (p.97). "To change values, it is recommended to use the override-values.yaml file ...Changing the default values.yaml file that comes with the chart is not recommended, as you might lose track of changes in the newer versions of the file.”! (It is a very good tip !)Ch.10 has some kubectl best practices and docker commands. I like the side by side equivalent of docker commands in kubectl. When the k8s API server is not responding, then these docker commands can help you troubleshoot more.Cons: there are a few syntax errors on p. 46, 53 and 70 when it should be double dashes " - -" but shown as single long dash "-" in the code block. Likely a formatting issue when published.

Amazon Verified review

Amazon Customer Mar 04, 2021

Thank you Eldad! JFrog rules the world. This book brought me up to speed from novice to expert in kubernetes and container management. It's easy to read, understand and apply the knowledge to simple and complex DevOps solutions. I'm very happy I came across this book after going through many such books on the topic. Thank you again for excellent work!

Rahul Agrawal Dec 05, 2020

I always wanted to learn more about kubectl commands i am so happy that I came across this book by Packt, I will recommend this to all

Dustin Dec 07, 2020

As other reviews have mentioned, this book does a great job of using kubectl to create and modify Kubernetes cluster resources. The official documentation can be overwhelming when new to Kubernetes. This book does a good job of aiding with order and structure to learn kubectl.This book also touches on kustomize and Helm, a nice surprise and not something often discussed while teaching kubectl.I would have enjoyed more detail on creating kubectl plugins. A more thorough chapter on creating plugins would make this book really stand out.

jjuarez Dec 07, 2020

I like the completion of the look over the tool capabilities, I don’t like that the book is, may be, quite short

kubectl: Command-Line Kubernetes in a Nutshell: Deploy, manage, and debug container workloads using the Kubernetes CLI

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kubectl: Command-Line Kubernetes in a Nutshell

Chapter 1: Introducing and Installing kubectl

Technical requirements

Introducing kubectl

Installing kubectl

Installing on macOS

Installing on Windows

Installing on Linux

kubectl commands

Basic commands

Deploy commands

Cluster management commands

Troubleshooting and debugging commands

Advanced commands

Settings commands

Other commands

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