Chapter 2. Using .NET Core 3.0 on Red Hat OpenShift Container Platform

If you are a system administrator or otherwise have sufficient permissions, change to the openshift project. Using the openshift project allows you to globally update the image stream definitions.

$ oc project openshift

If you do not have permissions to use the openshift project, you can still update your project definitions starting with Step 2.

Run the following commands to list all available .NET Core image versions.

$ oc describe is dotnet -n openshift
$ oc describe is dotnet

The output shows installed images or the message Error from server (NotFound) if no images are installed.

To pull the images, OpenShift needs credentials for authenticating with the registry.redhat.io server. These credentials are stored in a secret.

Enter the following command to list secrets. The first column shows the secret name.

$ oc get secret | grep kubernetes.io/dockerc

To check the contents of a secret, you can decode the .dockercfg or .dockerconfigjson data from Base64 format. This allows you to see if you already have credentials for the registry.redhat.io server. Enter the following command to show the .dockercfg section in a secret.

$ oc get secret <secret-name> -o yaml | grep .dockercfg
  .dockercfg: eyJyZWdpc3RyeS5yZWRoYXQuaW8iOnsidXNlcm5hbWUiOiIqKioqKioqKiIsInBhc3N3b3JkIjoiKioqKioqKioiLCJlbWFpbCI6InVudXNlZCIsImF1dGgiOiJLaW9xS2lvcUtpbzZLaW9xS2lvcUtpbz0ifX0=

Copy and paste the output in the following command to convert it from Base64 format. The example below shows the credentials for the registry.redhat.io server.

$ echo eyJyZWdpc3RyeS5yZWRoYXQuaW8iOnsidXNlcm5hbWUiOiIqKioqKioqKiIsInBhc3N3b3JkIjoiKioqKioqKioiLCJlbWFpbCI6InVudXNlZCIsImF1dGgiOiJLaW9xS2lvcUtpbzZLaW9xS2lvcUtpbz0ifX0= | base64 -d
{"registry.redhat.io":{"username":"********","password":"********","email":"unused","auth":"KioqKioqKio6KioqKioqKio="}}

You need to add a secret if there is no secret listed with credentials for the registry.redhat.io server.

Red Hat account credentials are used for registry.redhat.io access. If you are a customer with entitlements to Red Hat products, you already have account credentials to use. These are typically the same credentials used to log in to the Red Hat Customer Portal. To verify your Red Hat credentials, enter the following command and attempt to log in.

$ podman login registry.redhat.io

If you cannot log in, you first need to get an account with Red Hat. See Red Hat Container Registry Authentication for additional information. If you can log in, enter the following commands to create the secret.

$ oc create secret docker-registry redhat-registry \
    --docker-server=registry.redhat.io \
    --docker-username=<user-name> \
    --docker-password=<password> \
    --docker-email=unused
$ oc secrets link default redhat-registry --for=pull
$ oc secrets link builder redhat-registry

After creating the secret, enter the following command to import new image streams.

$ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json

If image streams were already installed, use the replace command to update the image stream definitions.

$ oc replace -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json

Run the following commands to deploy the ASP.NET Core application, which is in the app folder on the dotnetcore-3.0 branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository.

$ oc new-app --name=exampleapp 'dotnet:3.0~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-3.0' --build-env DOTNET_STARTUP_PROJECT=app

Use the oc logs command to track progress of the build.

$ oc logs -f bc/exampleapp

View the deployed application once the build is finished.

$ oc logs -f dc/exampleapp

At this point, the application is accessible within the project. To make it accessible externally, use the oc expose command. You can then use oc get routes to find the URL.

$ oc expose svc/exampleapp
$ oc get routes

Publish your application as described in Publish Applications. For example, the following commands create a new web application and publish it.

$ dotnet new web -o webapp
$ cd webapp
$ dotnet publish -c Release

Create a new binary build using the oc new-build command.

$ oc new-build --name=mywebapp dotnet:3.0 --binary=true

Start a build using the oc start-build command, specifying the path to the binary artifacts on your local machine.

$ oc start-build mywebapp --from-dir=bin/Release/netcoreapp3.0/publish

Create a new application using the oc new-app command.

$ oc new-app mywebapp

Change to the project where Jenkins is (or will be) deployed.

$ oc project <projectname>

Create a dotnet-jenkins-slave.yaml file. The value used for the <serviceAccount> element is the account used by the Jenkins slave. If no value is specified, the default service account is used.

kind: ConfigMap
apiVersion: v1
metadata:
  name: dotnet-jenkins-slave-30
  labels:
    role: jenkins-slave
data:
  dotnet30: |-
    <org.csanchez.jenkins.plugins.kubernetes.PodTemplate>
      <inheritFrom></inheritFrom>
      <name>dotnet-30</name>
      <instanceCap>2247483647</instanceCap>
      <idleMinutes>0</idleMinutes>
      <label>dotnet-30</label>
      <serviceAccount>jenkins</serviceAccount>
      <nodeSelector></nodeSelector>
      <volumes/>
      <containers>
        <org.csanchez.jenkins.plugins.kubernetes.ContainerTemplate>
          <name>jnlp</name>
          <image>registry.access.redhat.com/dotnet/dotnet-30-jenkins-slave-rhel7:latest</image>
          <privileged>false</privileged>
          <alwaysPullImage>true</alwaysPullImage>
          <workingDir>/tmp</workingDir>
          <command></command>
          <args>${computer.jnlpmac} ${computer.name}</args>
          <ttyEnabled>false</ttyEnabled>
          <resourceRequestCpu></resourceRequestCpu>
          <resourceRequestMemory></resourceRequestMemory>
          <resourceLimitCpu></resourceLimitCpu>
          <resourceLimitMemory></resourceLimitMemory>
          <envVars/>
        </org.csanchez.jenkins.plugins.kubernetes.ContainerTemplate>
      </containers>
      <envVars/>
      <annotations/>
      <imagePullSecrets/>
      <nodeProperties/>
    </org.csanchez.jenkins.plugins.kubernetes.PodTemplate>

Import the configuration into the project.

$ oc create -f dotnet-jenkins-slave.yaml

The slave image can now be used.

Create the buildconfig.yaml file.

kind: BuildConfig
apiVersion: v1
metadata:
  name: dotnetapp-build
spec:
  strategy:
    type: JenkinsPipeline
    jenkinsPipelineStrategy:
      jenkinsfile: |-
        node("dotnet-30") {
          stage('clone sources') {
            sh "git clone https://github.com/redhat-developer/s2i-dotnetcore-ex --branch dotnetcore-3.0 ."
          }
          stage('publish') {
            dir('app') {
              sh "dotnet publish -c Release"
            }
          }
          stage('create image') {
            dir('app') {
              sh 'oc new-build --name=dotnetapp dotnet:3.0 --binary=true || true'
              sh 'oc start-build dotnetapp --from-dir=bin/Release/netcoreapp3.0/publish --follow'
            }
          }
        }

Import the BuildConfig file to OpenShift.

$ oc create -f buildconfig.yaml

Click Start Pipeline. It may take a while for the build to start because the Jenkins image(s) need to be downloaded first.

During the build you can watch the different pipeline stages complete in the OpenShift console. You can also click View Log to see the pipeline stages complete in Jenkins.