Using Docker

Preface

Containers are a lightweight and portable store for an application and its dependencies.

Written down by itself, this sounds dry and boring. But the process improvements made possible by containers are anything but; used correctly, containers can be game-changing. So persuasive is the lure of the architectures and workflows made possible by containers that in the span of a year, it feels like every major IT company has gone from never having heard of Docker or containers to actively investigating and using them.

The rise of Docker has been astonishing. I don’t remember any technology that has had such a fast and profound effect on the IT industry. This book is my attempt to help you understand why containers are so important, what you stand to gain from adopting containerization, and most importantly, how to go about it.

Who Should Read This Book

This book tries to take a holistic approach to Docker, explaining the reasons for using Docker and showing how to use it and how to integrate it into a software development workflow. The book covers the entire software lifecycle, from development through to production and maintenance.

I have tried to avoid assuming too much of the reader beyond a basic knowledge of Linux and software development in general. The intended readership is primarily software developers, operations engineers, and system administrators (particularly those keen to develop a DevOps approach), but technically informed managers and enthusiasts should also be able to get something out of this book.

Why I Wrote This Book

I was in the fortunate position to learn about and use Docker while it was still in the early stages of its meteoric rise. When the opportunity to write this book appeared, I leapt at it with both hands. If my scribblings can help some of you to understand and make the most of the containerization movement, I will have achieved more than I have in years of developing software.

I truly hope that you enjoy reading this book and that it helps you on the path to using Docker in your organization.

Navigating This Book

This book is roughly organized as follows:

• Part I starts by explaining what containers are and why you should be interested in them, before going into a couple tutorial chapters showing the basics of Docker. It concludes with a lengthy chapter explaining the fundamental concepts and technology in Docker, including an overview of the various Docker commands.

• Part II explains how to use Docker in a software development lifecycle. It starts by showing how to set up a development environment, before building a simple web application that is used as an ongoing example throughout the subsequent chapters. This part covers development, testing, and integration, as well as how to deploy containers and how to effectively monitor and log a production system.

• Part III goes into advanced details and the tools and techniques needed to run multihost clusters of Docker containers safely and reliably. If you are already using Docker and need to understand how to scale up or solve networking and security issues, this is for you.

Conventions Used in This Book

The following typographical conventions are used in this book:

Italic

Indicates new terms, URLs, email addresses, filenames, and file extensions.

Constant width

Used for program listings, as well as within paragraphs to refer to program elements such as variable or function names, databases, data types, environment variables, statements, and keywords.

Constant width bold

Shows commands or other text that should be typed literally by the user.

Constant width italic

Shows text that should be replaced with user-supplied values or by values determined by context.

Tip

This element signifies a tip or suggestion.

Note

This element signifies a general note.

Warning

This element indicates a warning or caution.

Using Code Examples

Supplemental material (code examples, exercises, etc.) is available for download at https://github.com/using-docker/.

This book is here to help you get your job done. In general, if example code is offered with this book, you may use it in your programs and documentation. You do not need to contact us for permission unless you’re reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O’Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product’s documentation does require permission.

We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: “Using Docker by Adrian Mouat (O’Reilly). Copyright 2016 Adrian Mouat, 978-1-491-91576-9.”

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact us at [e-mail].

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Acknowledgments

I am immensely grateful for all the help, advice, and criticism I received during the writing of this book. If I missed your name in the following list, please accept my apologies; your contribution was appreciated whether I acted on it or not.

For their generous feedback, I would like to thank Ally Hume, Tom Sugden, Lukasz Guminski, Tilaye Alemu, Sebastien Goasguen, Maxim Belooussov, Michael Boelen, Ksenia Burlachenko, Carlos Sanchez, Daniel Bryant, Christoffer Holmstedt, Mike Rathbun, Fabrizio Soppelsa, Yung-Jin Hu, Jouni Miikki, Dale Bewley, Alex Ott and Thomas Demmig.

For technical conversations and input on specific technologies in the book, I would like to thank Andrew Kennedy, Peter White, Alex Pollitt, Fintan Ryan, Shaun Crampton, Spike Curtis, Alexis Richardson, Ilya Dmitrichenko, Casey Bisson, Thijs Schnitger, Sheng Liang, Timo Derstappen, Puja Abbassi, Alexander Larsson, and Kelsey Hightower. For allowing me to reuse monsterid.js, I would like to thank Kevin Gaudin.

For all their help, I would like to thank the O’Reilly staff, in particular my editors, Brian Anderson and Meghan Blanchette, for starting the whole process.

Diogo Mónica and Mark Coleman—thanks to both of you for answering my last-minute plea for help.

A particular shout-out has to go to two companies: Container Solutions and CloudSoft. Jamie Dobson and Container Solutions kept me busy blogging and speaking at events, and put me in contact with several people who had an impact on this book. The folks at CloudSoft graciously allowed me to use their office during the writing of this book and hosted the Edinburgh Docker meetup, both of which were very important to me.

For putting up with my obsession and moaning over the book, I would like to thank all my friends and family; you know who you are (and are unlikely to read this anyway).

Finally, I would like to thank the BBC 6 Music DJs who provided the soundtrack to this book, including Lauren Laverne, Radcliffe and Maconie, Shaun Keaveny, and Iggy Pop.