OpenShift v3

Archived

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Basics

Workflow

  1. After you create a new app (see below for instructions), OpenShift will first build it
    1. OpenShift spins up a new build container. Because this container is just for building, its resources will be listed under compute-resources-timebound if you go to Resources > Quota
    2. OpenShift will choose an appropriate Docker image based on the framework/DB you picked from the catalog
      • For example, if you picked Nodejs, a Docker image with Node.js will automatically be selected (e.g. openshift/nodejs:latest)
    3. Once the build container is running, it performs the build by taking your git repository and combining it with the Docker image into a new Docker image using a process called S2I (Source-to-Image)
      • You can see this image by going to Builds > Images. The image stream will be something like project/appname:tag
  2. OpenShift will then deploy your app
    1. OpenShift will now create a deployment container. This container will create and start the container that’s actually responsible for running your application, based on the new Docker image it created during the build step
      • The deployment container, like the build container, will use terminating resources and will be listed under compute-resources-timebound if you go to Resources > Quota
      • The application container will use non-terminating resources and will be listed under compute-resources if you go to Resources > Quota

Terminology

  • A project can have multiple applications
  • An application can have multiple pods
  • A pod is built from a docker image plus a repo, then deployed
  • An Image Stream is an abstract, flexible way to reference an actual Docker Image

Applications

Set up a new app

  1. Create a new project
  2. Add to Project > Browse Catalog
  3. Pick a framework, etc
  4. Continue to fill out the form as instructed
    • You’ll typically at a minimum need to provide the application name and git repository

Stop an app

  1. Go to Applications > Deployments
  2. Click on the build number of the application you wish to stop
  3. Find the circle that shows how many pods are running, and click the down arrow until it says 0 pods

Builds

Get webhook URL

  1. Using oc, get the build configuration

     oc describe buildconfig

  2. Look for Webhook GitHub or Webhook Generic and copy the URL

  3. In the OpenShift web interface, go to Applications > Builds > click the build for your application > Actions > Edit > Show advanced options

  4. Scroll down to Triggers > click the toggle button next to the secret for the webhook (GitHub or Generic) > copy the secret

  5. Replace the secret in the webhook URL with the secret you copied and configure it in your Git/build server as desired

Secrets

Configure SSH keys for a private Git repository

https://blog.openshift.com/private-git-repositories-part-2a-repository-ssh-keys/

CLI reference

Set up CLI tools

https://docs.openshift.com/online/cli_reference/get_started_cli.html

Login

In the web interface click ? > Command Line Tools and copy the line starting with oc login

SSH to a pod

  1. List pods

     oc get pods

  2. SSH to the desired pod

     oc rsh podname

List everything in a project

oc get all

Delete everything in a project

  1. Delete everything except secrets and persistent volume claims

     oc delete all --all

  2. Delete any secrets

     oc get secrets
 oc delete secrets ...

  3. Delete persistent volume claims

     oc delete pvc --all

Delete an app

Note: this can be done from the Web UI, you’d just have to delete all the components individually

  1. Get the label for the app you want to delete (look in the LABELS column) 
     oc get all --show-labels
  2. Delete the app by deleting everything with that label 
     oc delete all -l app=APPLABEL
  3. Delete secrets and persistent volume claims 
     oc get secrets
 oc delete secrets ...
 oc get pvc
 oc delete pvc ...

Templates

Create a template from an existing project

Follow the steps here: https://github.com/bmaupin/kleanup#usage

See also: https://docs.openshift.com/container-platform/latest/dev_guide/templates.html#export-as-template

Common Problems

Build is pending and never starts

Builds seem to frequently hang. Provided there are no errors this can often be fixed by manually redoing the build:

  1. Go to Builds > Builds and click the build number
  2. Go to Events and make sure there are no errors
  3. Go to Details and make sure the Duration is greater than 5 minutes. If not, wait a little bit longer.
  4. If there are no errors, at the top click Cancel Build > Rebuild