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

Executing a command in a running container

So, we have learned how to troubleshoot pods with pod describe and logs, but there might be some cases when you want to do even more advanced troubleshooting, such as checking some config files or running some commands in the container. These things can be done using the kubectl exec command, which will allow exec into the container and have an interactive session in the container or run your commands as well.

Let's see how to get the postgresql.conf file content using the kubectl exec command:

$ kubectl exec postgresql-57578b68d9-6wvpw cat \ /opt/bitnami/postgresql/conf/postgresql.conf
# -----------------------------
# PostgreSQL configuration file
# -----------------------------
# This file consists of lines of the form:
#   name = value
# (The "=" is optional.)  Whitespace may be used.  Comments are introduced with
# "#" anywhere on a line.  The complete list...