Docker and Makefiles

Difficulty: Beginner

Estimated Time: 10 minutes

In this scenario you will learn how to use Make for managing docker image creation.

Like source code, Docker images are required to be built, tested and deployed. While Docker doesn't have a build framework, you can take advantage of Make to automate the build process across different environments.

Makefiles are text files that provide a simple way to organise code compilation, or in this case Docker image compilation, into named targets. They are used by the make utility in order to execute the required commands to complete an action, such as build a docker images. These Makefiles can contain multiple different targets allowing for a centralised place to store the commands required to build, test, debug and push docker images.

In this scenario we'll explore how to create a Makefile that builds a Docker image.

This was created based on http://blog.benhall.me.uk

As demonstrated in this scenario, Makefiles make it really easy to manage the creation of Docker images. By having a single file you can organise the required commands for creating, debugging and releasing in a single and consistent approach.

NAME = benhall/docker-make-demo
  
  default: build
  
  build:
      docker build -t $(NAME) .
  
  push:
      docker push $(NAME)
  
  debug:
      docker run --rm -it $(NAME) /bin/bash
  
  run:
      docker run --rm $(NAME)
  
  release: build push

Your environment is currently being packaged as a Docker container and the download will begin shortly. To run the image locally, once Docker has been installed, use the commands

cat scrapbook_ben_hall_1_container.tar | docker load

docker run -it /ben_hall_1:

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Step 1 of 5

Step 1 - Dockerfile

This scenario has a Dockerfile which defines a Docker container to output the current date.

The command docker build -t benhall/docker-make-example . will create a Docker image is a friendly tag benhall/docker-make-example which we can use when starting a container based on the image.

In the next step we'll demostrate how to use this command inside a Makefile.

Step 2 - Makefile

The format of a Makefile is very simple. You start by defining a name for your target. The target is a collection of commands that need to be performed to complete an action, such as building the Docker image. The example below defines a target called MyTask which executes a script called mycommand.

MyTask:
    ./mycommand

Task

Use the editor to create a Makefile with a target called build that executes the command docker build -t benhall/docker-make-example .

Protip

Make requires Makefiles to use tabs for intention. Using spaces will cause the error Makefile:2: * missing separator. Stop.

build:
    docker build -t benhall/docker-make-example .

Step 4 - Additional Commands

Makefiles become extremely useful when they define all the different aspects of the build as different targets. Each target can either be executed independently or chained together.

Task

Create a second target called run that launches the newly created docker image using the command docker run benhall/docker-make-example

run:
    docker run benhall/docker-make-example

Step 5 - Setting Default Command

By default make will execute the first target in the file. You can specify a default by creating a target named default which links to an existing target.

By listing multiple targets you can chain their execution together.

For example to build and then launch the tests as default our target would be:

default: build test

Makefile

Terminal

cd <directory>	Change directory
ls	List directory
echo 'contents' > <file>	Write contents to a file
cat <file>	Output contents of file

i	In Command Mode	Change into Insert Mode, you can now insert and edit text in the file
esc	In Insert Mode	Change into Command Mode, you can now execute commands
:wq	In Command Mode	Save and Exit

Welcome!

Docker and Makefiles

Congratulations!

You've completed the scenario!

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