Book Image

Docker Quick Start Guide

By : Earl Waud
Book Image

Docker Quick Start Guide

By: Earl Waud

Overview of this book

Docker is an open source software platform that helps you with creating, deploying, and running your applications using containers. This book is your ideal introduction to Docker and containerization. You will learn how to set up a Docker development environment on a Linux, Mac, or Windows workstation, and learn your way around all the commands to run and manage your Docker images and containers. You will explore the Dockerfile and learn how to build your own enterprise-grade Docker images. Then you will learn about Docker networks, Docker swarm, and Docker volumes, and how to use these features with Docker stacks in order to define, deploy, and maintain highly-scalable, fault-tolerant multi-container applications. Finally, you will learn how to leverage Docker with Jenkins to automate the building of Docker images and the deployment of Docker containers. By the end of this book, you will be well prepared when it comes to using Docker for your next project.
Table of Contents (10 chapters)

The ONBUILD instruction

The ONBUILD instruction is a tool used when creating images that will become the parameter to the FROM instructions in another Dockerfile. The ONBUILD instruction just adds metadata to your image, specifically a trigger that is stored in the image and not otherwise used. However, that metadata trigger does get used when your image is supplied as the parameter in the FROM command of another Dockerfile. Here is the ONBUILD instruction syntax:

# ONBUILD instruction syntax
ONBUILD [INSTRUCTION]

The ONBUILD instruction is kind of like a Docker time machine used to send instructions into the future. (You might laugh if you knew how many times I just typed Doctor time machine!) Let's demonstrate the use of the ONBUILD instruction with a simple example. First, we will build an image named my-base using the following Dockerfile:

# my-base Dockerfile
FROM alpine...