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Learn OpenShift

Learn OpenShift

By : Denis Zuev, Artemii Kropachev, Aleksey Usov
3 (2)
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Learn OpenShift

Learn OpenShift

3 (2)
By: Denis Zuev, Artemii Kropachev, Aleksey Usov

Overview of this book

Docker containers transform application delivery technologies to make them faster and more reproducible, and to reduce the amount of time wasted on configuration. Managing Docker containers in the multi-node or multi-datacenter environment is a big challenge, which is why container management platforms are required. OpenShift is a new generation of container management platforms built on top of both Docker and Kubernetes. It brings additional functionality to the table, something that is lacking in Kubernetes. This new functionality significantly helps software development teams to bring software development processes to a whole new level. In this book, we’ll start by explaining the container architecture, Docker, and CRI-O overviews. Then, we'll look at container orchestration and Kubernetes. We’ll cover OpenShift installation, and its basic and advanced components. Moving on, we’ll deep dive into concepts such as deploying application OpenShift. You’ll learn how to set up an end-to-end delivery pipeline while working with applications in OpenShift as a developer or DevOps. Finally, you’ll discover how to properly design OpenShift in production environments. This book gives you hands-on experience of designing, building, and operating OpenShift Origin 3.9, as well as building new applications or migrating existing applications to OpenShift.
Table of Contents (24 chapters)
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Separating configuration from application code using ConfigMaps

The ConfigMap resource is used to separate data from a pod running an application. These kinds of resource contain arbitrary data to be injected into a pod as configuration. Injection in this context means that the pod can use it in the following ways:

  • Export its key/value pairs as environment variables
  • Supply its values as command-line arguments to the application
  • Mount it as a volume inside the pod to the location where the application expects to find its configuration file

Before you begin, make sure you are logged in as an unprivileged user for the most representative experience:

# oc login -u alice

Let's look at the process of exporting ConfigMap as an environment variable into a container. First, we have to create ConfigMap itself from a list of environment variables:

# cat example.env 
VAR_1=Hello
VAR_2...

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