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Learn OpenShift

You're reading from   Learn OpenShift Deploy, build, manage, and migrate applications with OpenShift Origin 3.9

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Product type Paperback
Published in Jul 2018
Publisher Packt
ISBN-13 9781788992329
Length 504 pages
Edition 1st Edition
Languages
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Authors (3):
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Denis Zuev Denis Zuev
Author Profile Icon Denis Zuev
Denis Zuev
Aleksey Usov Aleksey Usov
Author Profile Icon Aleksey Usov
Aleksey Usov
Artemii Kropachev Artemii Kropachev
Author Profile Icon Artemii Kropachev
Artemii Kropachev
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Toc

Table of Contents (24) Chapters Close

Preface 1. Containers and Docker Overview FREE CHAPTER 2. Kubernetes Overview 3. CRI-O Overview 4. OpenShift Overview 5. Building an OpenShift Lab 6. OpenShift Installation 7. Managing Persistent Storage 8. Core OpenShift Concepts 9. Advanced OpenShift Concepts 10. Security in OpenShift 11. Managing OpenShift Networking 12. Deploying Simple Applications in OpenShift 13. Deploying Multi-Tier Applications Using Templates 14. Building Application Images from Dockerfile 15. Building PHP Applications from Source Code 16. Building a Multi-Tier Application from Source Code 17. CI/CD Pipelines in OpenShift 18. OpenShift HA Architecture Overview 19. OpenShift HA Design for Single and Multiple DCs 20. Network Design for OpenShift HA 21. What is New in OpenShift 3.9? 22. Assessments 23. Other Books You May Enjoy

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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