Book Image

Learning Docker - Second Edition

By : Vinod Singh, Pethuru Raj, Jeeva S. Chelladhurai
Book Image

Learning Docker - Second Edition

By: Vinod Singh, Pethuru Raj, Jeeva S. Chelladhurai

Overview of this book

Docker is an open source containerization engine that offers a simple and faster way for developing and running software. Docker containers wrap software in a complete filesystem that contains everything it needs to run, enabling any application to be run anywhere – this flexibily and portabily means that you can run apps in the cloud, on virtual machines, or on dedicated servers. This book will give you a tour of the new features of Docker and help you get started with Docker by building and deploying a simple application. It will walk you through the commands required to manage Docker images and containers. You’ll be shown how to download new images, run containers, list the containers running on the Docker host, and kill them. You’ll learn how to leverage Docker’s volumes feature to share data between the Docker host and its containers – this data management feature is also useful for persistent data. This book also covers how to orchestrate containers using Docker compose, debug containers, and secure containers using the AppArmor and SELinux security modules.

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Table of Contents (13 chapters)
Preface
Preface
What this book covers
What you need for this book
Who this book is for
Conventions
Reader feedback
Customer support
Free Chapter
1
Getting Started with Docker
Getting Started with Docker
The key drivers for Dockerization
Differentiating between containerization and virtualization
Installing the Docker Engine
Understanding the Docker setup
Downloading the first Docker image
Running the first Docker container
Summary
2
Handling Docker Containers
Handling Docker Containers
Clarifying Docker terms
Working with Docker images
Working with an interactive container
Summary
3
Building Images
Building Images
Docker's integrated image building system
A quick overview of the Dockerfile's syntax
The Dockerfile build instructions
A brief on the Docker image management
Best practices for writing a Dockerfile
Summary
4
Publishing Images
Publishing Images
Understanding Docker Hub
Pushing images to Docker Hub
Automating the build process for images
Private repositories on Docker Hub
Organizations and teams on Docker Hub
The REST API for Docker Hub
Summary
5
Running Your Private Docker Infrastructure
Running Your Private Docker Infrastructure
Docker Registry
Docker Registry use cases
Running Docker Registry and pushing the image
Running the Docker Registry on localhost with an SSL certificate
Running Docker Registry with restrictions
Managing Docker Registry with Docker Compose
Load balancing consideration
Webhook notifications
Docker Registry HTTP API support
Summary
6
Running Services in a Container
Running Services in a Container
A brief overview of container networking
Envisaging container as a service
Exposing container services
Summary
7
Sharing Data with Containers
Sharing Data with Containers
Data volume
The volume management command
Sharing host data
Sharing data between containers
Avoiding common pitfalls
Summary
8
Orchestrating Containers
Orchestrating Containers
Docker inbuilt service discovery
Linking containers
Orchestration of containers
Summary
9
Testing with Docker
Testing with Docker
A brief overview of TDD
Testing your code inside Docker
Integrating Docker testing into Jenkins
Summary
10
Debugging Containers
Debugging Containers
Process-level isolation for Docker containers
The docker exec command
The docker ps command
The docker top command
The docker stats command
The Docker events command
The docker logs command
The docker attach command
Debugging a Dockerfile
Summary
11
Securing Docker Containers
Securing Docker Containers
The security scenario in the containerization domain
Immutable infrastructure
The best practices for container security
Summary
12
The Docker Platform – Distinct Capabilities and Use Cases
The Docker Platform – Distinct Capabilities and Use Cases
Describing containers
Briefing the Docker platform
Implications of the Docker technology
The Docker use cases
Summary

Debugging a Dockerfile

Sometimes creating a Dockerfile may not start with everything working. A Dockerfile does not always build images and sometimes it does, but starting a container would crash on startup.

Every instruction we set in the Dockerfile is going to be built as a separate, temporary image for the other instruction to build itself on top of the previous instruction. The following example explains this:

  1. Create a Dockerfile using your favorite editor:
      FROM busybox 
      RUN ls -lh 
      CMD echo Hello world
  1. Now, build the image by executing the following command:
      $ docker build .
      Sending build context to Docker daemon 2.048 kB
      Step 1 : FROM busybox
      latest: Pulling from library/busybox
      56bec22e3559: Pull complete 
      Digest: sha256:29f5d56d12684887bdfa50dcd29fc31eea4aaf4ad3bec43daf19026a7ce69912
      Status: Downloaded newer image for busybox:latest
      ---> e02e811dd08f...
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