Unit 2 Chapter 1: Custom Docker Image

What's the point?

A Docker image can be used to provide a pre-built, pre-installed, and pre-configured development environment.
The custom Docker images for the app should include all necessary software that's time-consuming to install. This makes it easy to set up your development environment and to quickly reset it to initial conditions.
When you reset your development environment, git clone the Rails app in the Docker container, and run the build_fast.sh script in the app, you should be ready to roll. This should take just a few minutes, not hours.

It is assumed here that you are familiar with the special Ruby on Racetracks way of using Docker. This is covered in the Different Docker Tutorial.

Copy the Docker image creation repository from the Different Docker Tutorial. Remove everything the .git directory, git init your repository, and push it to your own BitBucket (or GitHub) account.
Remove all directories except for the rails-general and 32rails-general directories. Git add, commit, and push these changes.
Rename the rails-general and 32rails-general directories. Rename the check-rails-general, rails-general-root, and rails-general-user scripts within the rails-general/usr_local_bin directory. Git add, commit, and push these changes.
Use the SearchMonkey tool to find all instances of "rubyonracetracks" and replace them with your username. Git add, commit, and push this change.
Use the SearchMonkey tool to find all instances of "rails-general" and replace them with the appropriate name. Git add, commit, and push these changes.
Update the scripts within the usr_local_bin directory for your Docker image, especially the rails-*-user script.
- Check the Gemfile and Gemfile.lock files for the correct version of the Ruby language and the ffi, nokogiri, pg, rails gems. (Having these elements in the custom Docker image speeds up the setup process of your Rails app.)
- Check the Rails app's setup instructions to see if there's anything else you need to add, such as PostgreSQL extensions or PhantomJS.
- You may need to revisit this step later. Git add, commit, and push these changes.
Update the README.md file. Git add, commit, and push these changes.

If you haven't already done so, create an account on Docker Hub.
Add a repository for the custom 32-bit Docker image for the Rails app.
Add an automated build for the custom 64-bit Docker image for the Rails app. Set the build to automatically be triggered when the 64-bit development Docker image (the one your Docker image is based on) is updated.
Start the automated build for your 64-bit Docker image. If all goes well, you're ready to move on. If not, you'll need to revisit the previous section in this chapter and update the scripts.

Go back to the terminal window within your Docker image build repository. Go to the directory for the 32-bit version of the Rails project's custom Docker image. Enter the command "sh build.sh" to start the build process.
At the end of the build process, you will see the sanity checks, and you will be asked if you wish to push the new image. If all goes well, enter "y" for yes. If not, enter "n" for no, and fix the code for building the Docker image.

Copy the Docker image usage repository from the Different Docker Tutorial. Remove everything the .git directory, git init your repository, and push it to your own BitBucket (or GitHub) account.
Remove the scripts in the root directory for using the minimal, development, and Javascript images. Git add, commit, and push these changes.
Rename the rails-general.sh script. Git add, commit, and push this change.
Use the SearchMonkey tool to find all instances of "rubyonracetracks" and replace them with your username. Git add, commit, and push this change.
Use the Searchmonkey tool to find all instances of "rails-general" and replace them with the appropriate name. Git add, commit, and push these changes.
Update the README.md file. Git add, commit, and push these changes.
On both 64-bit and 32-bit Debian Stable Linux systems, download and boot up your new Docker image. Run the info.sh script in the shared directory to confirm that everything works as expected.

When you are able to download and use your custom Docker images, you are ready to move on to the next chapter.
You may need to revisit this chapter later.