| File | Required? | Description |
|---|---|---|
| Dockerfile | Yes | Defines the base builder image |
| s2i/bin/assemble | Yes | Script that builds the application |
| s2i/bin/usage | No | Script that prints the usage of the builder |
| s2i/bin/run | Yes | Script that runs the application |
| s2i/bin/save-artifacts | No | Script for incremental builds that saves the built artifacts |
| test/run | No | Test script for the builder image |
| test/test-app | Yes | Test application source code |
Create a Dockerfile that installs all of the necessary tools and libraries that are needed to build and run our application. This file will also handle copying the s2i scripts into the created image.
Create an assemble script that will build our application, e.g.:
- build python modules
- bundle install ruby gems
- setup application specific configuration
The script can also specify a way to restore any saved artifacts from the previous image.
Create a run script that will start the application.
Create a save-artifacts script which allows a new build to reuse content from a previous version of the application image.
Create a usage script that will print out instructions on how to use the image.
Make sure that all of the scripts are executable by running chmod +x s2i/bin/*
The following command will create a builder image named nginx-centos7 based on the Dockerfile that was created previously.
docker build -t nginx-centos7 .
The builder image can also be created by using the make command since a Makefile is included.
Once image has finished building, the command s2i usage nginx-centos7 will print out the help info that was defined in the usage script.
The builder image can be tested using the following commands:
docker build -t nginx-centos7-candidate .
IMAGE_NAME=nginx-centos7-candidate test/run
The builder image can also be tested by using the make test command since a Makefile is included.
The application image combines the builder image with your applications source code, which is served using whatever application is installed via the Dockerfile, compiled using the assemble script, and run using the run script. The following command will create the application image:
s2i build test/test-app nginx-centos7 nginx-centos7-app
---> Building and installing application from source...
Using the logic defined in the assemble script, s2i will now create an application image using the builder image as a base and including the source code from the test/test-app directory.
Running the application image is as simple as invoking the docker run command:
docker run -d -p 8080:8080 nginx-centos7-app
The application, which consists of a simple static web page, should now be accessible at http://localhost:8080.
Rebuilding the application using the saved artifacts can be accomplished using the following command:
s2i build --incremental=true test/test-app nginx-centos7 nginx-app
---> Restoring build artifacts...
---> Building and installing application from source...
This will run the save-artifacts script which includes the custom code to backup the currently running application source, rebuild the application image, and then re-deploy the previously saved source using the assemble script.
It is possible to configure nginx server itself via this s2i builder image. To do so, simply provide an nginx.conf file in the root directory of your application. The s2i/bin/assemble will find this configuration file and make nginx use it. See the example configuration file in test/test-app-redirect/ directory. You can build and run it by using these commands:
s2i build test/test-app-redirect nginx-centos7 nginx-centos7-redirect
docker run -d -p 8080:8080 nginx-centos7-redirect
Going to http://localhost:8080 should now redirect you to https://openshift.com.
More generally, it is possible to configure any kind of service using s2i, assuming that the provided assemble and/or run scripts support this and can recognize and use provided configuration files. It's also possible, assuming the s2i image supports it, to provide scripts that get executed by the s2i run script to further customize the functionality. Some more advanced examples of this can be found at https://github.com/sclorg/mongodb-container and https://github.com/sclorg/mariadb-container/.