Docker and Makefiles by ben_hall

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.

To complete this step you need to execute the following code:

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

Step 3 - Executing Make

Once the Makefile has been updated it can be used by the make utility. After executing, the utility will output the logs and if successful the artifacts will be created.

Task

Execute the build command for the image using make

Protip

You can find the additional command options using make --help. To see the Docker image create use the command docker images

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

To complete this step you need to execute the following code:

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

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

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ben_hall - Docker and Makefiles

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