DevOps Katas: Mastering DevOps Practices/

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Jenkins Kata 5: Docker Container Build Step

Jenkins Kata 5: Docker Container Build Step

Learn about adding a Dockerfile, installing a Docker plugin, running a private Docker repository, and adding a Docker build step.

We'll cover the following...

Step 1: Add a Dockerfile

To do this:

  • Use the NGINX image and copy the files to the container.
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nano Dockerfile
  • Enter the following into the text editor:
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FROM nginx
ADD storelist.htm store.png style.css /usr/share/nginx/html/
  • Save the changes.

Build the Dockerfile as follows:

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docker build -t storelist_image .

Command's Parameters

Command / Parameter

Description

docker build

This is the parent command. Docker build creates a new image from a Dockerfile.

-t

This adds a tag to the image.

storelist_image

This is the tag to be added to the new image.

.

This is a reference to the local directory, which indicates to the docker command where to find the Dockerfile.

Cody’s first step in containerizing the “web-storelist” application is to add a Dockerfile. The Dockerfile contains directives that copy the files of the application to an image based on the official NGINX image. NGINX is an open-source HTTP server. Cody then tests the Dockerfile by building it manually with the docker build command.

Run the image locally as follows:

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docker container run -d -p 81:80 storelist_image

Command's Parameters

Command / Parameter

Description

container

This is the parent command. The container parent command executes commands related to containers.

run

The run command runs a container.

-p

This maps ports between the container and the host.


80:80

This is the value used by the -p parameter to map ports. This value maps port 80 on the host to port 80 in the container. Requests to port 80 on the host IP address will be routed to port 80 in the container.

storelist_image

This is the name of the image to run.

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curl localhost

Commands

Command / Parameter

Description

curl

The curl command sends an HTTP request to a URL and returns the response to the terminal.

localhost

This is an alias for the local computer.

The commands to add the Dockerfile to Cody’s repository index, commit, and push are given below:

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git add Dockerfile
git commit -a -m "Adding Dockerfile"
git push origin master #(username: cody.coder | password: katas)

Command's Parameters

Command / Parameter

Description

git commit

This creates a new commit in the local repository.

-a

This includes all modified files in the new commit.

-m

This sets the commit message in the command line.

"Adding Dockerfile"

This is the commit message that will be associated with the new commit.

git push

This pushes commits to a remote Git server. All local commits missing from the remote will be pushed.

origin

This is the registered name of the remote Git server. The default name is `origin`.

master

This is the name of the branch to push.

These commands commit the addition of the Dockerfile to the local “web-storelist” Git repository, then push that commit to the Gogs server. If we return to Jenkins, we should see a new, recent build in the “web-storelist” job. When the commit was pushed to Gogs, the webhook executed and triggered the build. We can also view the workspace of the job and should ...