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

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.