Getting Started Guide

.NET Core 2.1

Red Hat Customer Content Services


.NET Core is a general purpose development platform featuring automatic memory management and modern programming languages. It allows users to build high-quality applications efficiently. .NET Core is available in Red Hat Enterprise Linux and OpenShift Container Platform via certified containers.
.NET Core offers the following features:
  • The ability to follow a microservices-based approach, where some components are built with .NET and others with Java, but all can run on a common, supported platform in Red Hat Enterprise Linux and OpenShift Container Platform.
  • The capacity to more easily develop new .NET Core workloads on Microsoft Windows. Customers can deploy and run on either Red Hat Enterprise Linux or Windows Server.
  • A heterogeneous data center, where the underlying infrastructure is capable of running .NET applications without having to rely solely on Windows Server.
.NET Core 2.1 is supported on Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, and OpenShift Container Platform versions 3.3 and later.

Chapter 1. Using .NET Core 2.1 on Red Hat Enterprise Linux

This Getting Started Guide describes how to install .NET Core 2.1 on Red Hat Enterprise Linux (RHEL). See Red Hat Enterprise Linux documentation for more information about RHEL 7.

1.1. Install and Register Red Hat Enterprise Linux

  1. Install RHEL 7 using one of the following images:

  2. Use the following command to register the system.

    $ sudo subscription-manager register

    You can also register the system by following the appropriate steps in Registering and Unregistering a System in the Red Hat Subscription Management document.

  3. Display a list of all subscriptions that are available for your system and identify the pool ID for the subscription.

    $ sudo subscription-manager list --available

    This command displays the subscription name, unique identifier, expiration date, and other details related to it. The pool ID is listed on a line beginning with Pool ID.

  4. Attach the subscription that provides access to the dotNET on RHEL repository. Use the pool ID you identified in the previous step.

    $ sudo subscription-manager attach --pool=<appropriate pool ID from the subscription>
  5. Enable the .NET Core channel for Red Hat Enterprise 7 Server, Red Hat Enterprise 7 Workstation, or HPC Compute Node with one of the following commands, respectively.

    $ sudo subscription-manager repos --enable=rhel-7-server-dotnet-rpms
    $ sudo subscription-manager repos --enable=rhel-7-workstation-dotnet-rpms
    $ sudo subscription-manager repos --enable=rhel-7-hpc-node-dotnet-rpms
  6. Verify the list of subscriptions attached to your system.

    $ sudo subscription-manager list --consumed
  7. Install the scl tool.

    $ sudo yum install scl-utils

1.2. Install .NET Core

  1. Install .NET Core 2.1 and all of its dependencies.

    $ sudo yum install rh-dotnet21 -y
  2. Enable the rh-dotnet21 Software Collection environment so you can run dotnet commands in the bash shell

    This procedure installs the .NET Core 2.1 runtime with the latest 2.1 SDK. When a newer SDK becomes available, it automatically installs as a package update.

    $ scl enable rh-dotnet21 bash

    This command does not persist; it creates a new shell, and the dotnet command is only available within that shell. If you log out, use another shell, or open up a new terminal, the dotnet command is no longer enabled.


    Red Hat does not recommend permanently enabling rh-dotnet21 because it may affect other programs. For example, rh-dotnet21 includes a version of libcurl that differs from the base RHEL version. This may lead to issues in programs that do not expect a different version of libcurl. If you want to enable rh-dotnet permanently, add the following line to your ~/.bashrc file.

    source scl_source enable rh-dotnet21

  3. Run the following command to verify the installation succeeded.

    $ dotnet --info
    .NET Core SDK (reflecting any global.json):
     Version:   2.1.300
     Commit:    ded465c666
    Runtime Environment:
     OS Name:     rhel
     OS Version:  7
     OS Platform: Linux
     RID:         rhel.7-x64
     Base Path:   /opt/rh/rh-dotnet21/root/usr/lib64/dotnet/sdk/2.1.300/
    Host (useful for support):
      Version: 2.1.0
      Commit:  N/A
      .NET Core SDKs installed:
      2.1.300 [/opt/rh/rh-dotnet21/root/usr/lib64/dotnet/sdk]
    .... omitted

1.3. Create an Application

  1. Create a new Console application in a directory called hello-world.

    $ dotnet new console -o hello-world
      The template "Console Application" was created successfully.
      Processing post-creation actions...
      Running 'dotnet restore' on hello-world/hello-world.csproj...
      Restoring packages for /home/<USER>/hello-world/hello-world.csproj...
      Generating MSBuild file /home/<USER>/hello-world/obj/hello-world.csproj.nuget.g.props.
      Generating MSBuild file /home/<USER>/hello-world/obj/hello-world.csproj.nuget.g.targets.
      Restore completed in 224.85 ms for /home/<USER>/hello-world/hello-world.csproj.
      Restore succeeded.
  2. Run the project.

    $ cd hello-world
    $ dotnet run
    Hello World!

1.4. Publish Applications

The .NET Core 2.1 applications can be published to use a shared system-wide version of .NET Core or to include .NET Core. These two deployment types are called framework-dependent deployment (FDD) and self-contained deployment (SCD), respectively.

For RHEL, we recommend publishing by FDD. This method ensures the application is using an up-to-date version of .NET Core, built by Red Hat, that includes a specific set of native dependencies. These native libraries are part of the rh-dotnet21 Software Collection. On the other hand, SCD uses a runtime built by Microsoft. Running applications outside the rh-dotnet21 Software Collection may cause issues due to the unavailability of native libraries.

1.4.1. Publish .NET Core Applications

  1. Use the following command to publish a framework-dependent application.

    $ dotnet publish -f netcoreapp2.1 -c Release
  2. Optional: If the application is only for RHEL, trim out the dependencies needed for other platforms with these commands.

    $ dotnet restore -r rhel.7-x64
    $ dotnet publish -f netcoreapp2.1 -c Release -r rhel.7-x64 --self-contained false
  3. Enable the Software Collection and pass the application assembly name to the dotnet command to run the application on a RHEL system.

    $ scl enable rh-dotnet21 -- dotnet <app>.dll
  4. This command can be added to a script that is published with the application. Add the following script to your project and update the ASSEMBLY variable.

    DIR="$(dirname "$(readlink -f "$0")")"
    scl enable $SCL -- dotnet "$DIR/$ASSEMBLY" "$@"
  5. To include the script when publishing, add this ItemGroup to the csproj file.

        <None Update="<scriptname>" Condition="'$(RuntimeIdentifier)' == 'rhel.7-x64' and '$(SelfContained)' == 'false'" CopyToPublishDirectory="PreserveNewest" />

1.4.2. Publish ASP.NET Core Applications

When using the Microsoft SDK, ASP.NET Core 2.1 web applications are published with a dependency on the ASP.NET Core shared framework. This is a set of packages that are expected to be available on the runtime system.

When publishing on RHEL, these packages are included with the application. To include the packages using the Microsoft SDK, the MicrosoftNETPlatformLibrary property must be set to Microsoft.NETCore.App in the project file as shown below.

<Project Sdk="Microsoft.NET.Sdk.Web">
    <PackageReference Include="Microsoft.AspNetCore.App" Version="2.1" />

As an alternative, this property can be set when publishing the application.

$ dotnet publish -f netcoreapp2.1 -c Release -r rhel.7-x64 --self-contained false /p:MicrosoftNETPlatformLibrary=Microsoft.NETCore.App

1.5. Run Applications on Linux containers

This section shows how to use the dotnet/dotnet-21-runtime-rhel7 image to run a precompiled application inside a Linux container.

  1. Create a new mvc project in a directory named mvc_runtime_example.

    $ dotnet new mvc -o mvc_runtime_example --no-restore
    $ cd mvc_runtime_example
  2. Restore and publish the project.

    $ dotnet restore -r rhel.7-x64
    $ dotnet publish -f netcoreapp2.1 -c Release -r rhel.7-x64 --self-contained false /p:MicrosoftNETPlatformLibrary=Microsoft.NETCore.App
  3. Create the Dockerfile.

    $ cat > Dockerfile <<EOF
    ADD bin/Release/netcoreapp2.1/rhel.7-x64/publish/ .
    CMD ["dotnet", "mvc_runtime_example.dll"]
  4. Build your image.

    $ podman build -t dotnet-21-runtime-example .

    If you get an error containing the message unable to retrieve auth token: invalid username/password, you need to provide credentials for the server. Use the command $ podman login to log in. Your credentials are typically the same as those used for the Red Hat Customer Portal.

  5. Run your image.

    $ podman run -d -p8080:8080 dotnet-21-runtime-example
  6. View the result in a browser:

Report a bug

Chapter 2. Using .NET Core 2.1 on Red Hat OpenShift Container Platform

2.1. Installing Image Streams

The .NET Core image streams definition can be defined globally in the openshift namespace or locally in your specific project.

  1. 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.

  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.

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


    For OpenShift 3.11 and later, a secret is preconfigured for the openshift namespace.

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

    $ oc get secret | grep

    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 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 server.

    $ echo eyJyZWdpc3RyeS5yZWRoYXQuaW8iOnsidXNlcm5hbWUiOiIqKioqKioqKiIsInBhc3N3b3JkIjoiKioqKioqKioiLCJlbWFpbCI6InVudXNlZCIsImF1dGgiOiJLaW9xS2lvcUtpbzZLaW9xS2lvcUtpbz0ifX0= | base64 -d

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

  4. Red Hat account credentials are used for 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

    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-username=<user-name> \
        --docker-password=<password> \
    $ oc secrets link default redhat-registry --for=pull
    $ oc secrets link builder redhat-registry
  5. After creating the secret, enter the following command to import new image streams.

    $ oc create -f

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

    $ oc replace -f

2.2. Deploying Applications from Source

  1. Run the following commands to deploy the ASP.NET Core application, which is in the app folder on the dotnetcore-2.1 branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository.

    $ oc new-app --name=exampleapp 'dotnet:2.1~' --build-env DOTNET_STARTUP_PROJECT=app
  2. Use the oc logs command to track progress of the build.

    $ oc logs -f bc/exampleapp
  3. View the deployed application once the build is finished.

    $ oc logs -f dc/exampleapp
  4. 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

2.3. Deploying Applications from Binary Artifacts

The .NET Core S2I builder image can be used to build an application using binary artifacts that you provide.

  1. 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 /p:MicrosoftNETPlatformLibrary=Microsoft.NETCore.App
  2. Create a new binary build using the oc new-build command.

    $ oc new-build --name=mywebapp dotnet:2.1 --binary=true
  3. 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/netcoreapp2.1/publish
  4. Create a new application using the oc new-app command.

    $ oc new-app mywebapp

2.4. Using a Jenkins Slave

The OpenShift Container Platform Jenkins image provides auto-discovery of the .NET Core 2.1 slave image (dotnet-21). For auto-discovery to work, you need to add a Jenkins slave ConfigMap yaml file to the project.

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

    $ oc project <projectname>
  2. 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
      name: dotnet-jenkins-slave-21
        role: jenkins-slave
      dotnet21: |-
              <args>${computer.jnlpmac} ${}</args>
  3. Import the configuration into the project.

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

    The slave image can now be used.

Example: The following example shows a Jenkins pipeline added to OpenShift Container Platform. Note that when a Jenkins pipeline is added and no Jenkins master is running, OpenShift automatically deploys a master. See OpenShift Container Platform and Jenkins for additional information about deploying and configuring a Jenkins server instance.

In the example steps, the BuildConfig yaml file includes a simple Jenkins pipeline configured using the dotnet-21 Jenkins slave. There are three stages in the example BuildConfig yaml file:

  • First, the sources are checked out.
  • Second, the application is published.
  • Third, the image is assembled using a binary build. See Deploying Applications from Binary Artifacts for additional information about binary builds.

Complete the steps below to configure the example Jenkins master-slave pipeline.

  1. Create the buildconfig.yaml file.

    kind: BuildConfig
    apiVersion: v1
      name: dotnetapp-build
        type: JenkinsPipeline
          jenkinsfile: |-
            node("dotnet-21") {
              stage('clone sources') {
                sh "git clone --branch dotnetcore-2.1 ."
              stage('publish') {
                dir('app') {
                  sh "dotnet publish -c Release /p:MicrosoftNETPlatformLibrary=Microsoft.NETCore.App"
              stage('create image') {
                dir('app') {
                  sh 'oc new-build --name=dotnetapp dotnet:2.1 --binary=true || true'
                  sh 'oc start-build dotnetapp --from-dir=bin/Release/netcoreapp2.1/publish --follow'
  2. Import the BuildConfig file to OpenShift.

    $ oc create -f buildconfig.yaml
  3. Launch the OpenShift console. Go to Builds > Pipelines. The dotnetapp-build pipeline is available.
  4. 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.

  5. When the Jenkins pipeline build completes, go to Builds > Images. The dotnetapp image is built and available.

2.5. Environment Variables

The .NET Core images support a number of environment variables to control the build behavior of your .NET Core application. These variables can be set as part of the build configuration, or they can be added to an .s2i/environment file in the application source code repository.

Variable NameDescriptionDefault


Selects project to run. This must be a project file (for example, csproj or fsproj) or a folder containing a single project file.



Selects the assembly to run. This must not include the .dll extension. Set this to the output assembly name specified in csproj (PropertyGroup/AssemblyName).

The name of the csproj file


Specifies the space-separated list of NuGet package sources used during the restore operation. This overrides all of the sources specified in the NuGet.config file.



Specifies a list of .NET tools to install before building the app. It is possible to install a specific version by post pending the package name with @<version>.



Specifies a list of NPM packages to install before building the application.



Specifies the list of test projects to test. This must be project files or folders containing a single project file. dotnet test is invoked for each item.



Runs the application in Debug or Release mode. This value should be either Release or Debug.



Specifies the verbosity of the dotnet build commands. When set, the environment variables are printed at the start of the build. This variable can be set to one of the msbuild verbosity values (q[uiet], m[inimal], n[ormal], d[etailed], and diag[nostic]).



Configures the HTTP/HTTPS proxy used when building and running the application.



When set to true, the source code will not be included in the image.



Used to specify a list of folders/files with additional SSL certificates to trust. The certificates are trusted by each process that runs during the build and all processes that run in the image after the build (including the application that was built). The items can be absolute paths (starting with /) or paths in the source repository (for example, certificates).



Uses a custom NPM registry mirror to download packages during the build process.



This variable is set to http://*:8080 to configure ASP.NET Core to use the port exposed by the image. Changing this is not recommended.



When set to true, disables restoring multiple projects in parallel. This reduces restore timeout errors when the build container is running with low CPU limits.



When set to true, the NuGet packages will be kept so they can be re-used for an incremental build. Defaults to false.



When set to true, creates a tar.gz file at /opt/app-root/app.tar.gz that contains the published application.



Selects the default sdk version when building. If there is a global.json file in the source repository, that takes precedence. When set to latest, the latest sdk in the image is used.

Lowest sdk version available in the image

2.6. Sample Applications

Three sample applications are available:

  • dotnet-example: This is the default model–view–controller (MVC) application.
  • dotnet-runtime-example: This shows how to build an MVC application using a chained build. The application is built in dotnet/dotnet-21-rhel7. The result is deployed in dotnet/dotnet-21-runtime-rhel7. Note that chained builds are not supported on OpenShift Online.
  • dotnet-pgsql-persistent: This is the Microsoft ASP.NET Core MusicStore sample application using a PostgreSQL backend.

To add the samples using the OpenShift Web Console, browse to your project and click Add to project. You can filter for dotnet. If the samples do not show up, you can add them to your installation by running the following commands.

$ oc create -f
$ oc create -f
$ oc create -f

Report a bug

Chapter 3. Migrating to .NET Core 2.1

This chapter provides migration information for .NET Core 2.1.

3.1. Migrating from previous versions of .NET Core

Microsoft provides instructions for migrating from most previous versions of .NET Core. When migrating, the following ASP.NET Core 2.0 property should no longer be specified. It should remain the default value for .NET Core 2.1. Make sure to remove this property from the project file and command line, if it is being specified there.


See the following Microsoft articles to migrate from previous versions of .NET Core.


If migrating from .NET Core 1.x to 2.0, see the first few related sections in Migrate from ASP.NET Core 1.x to 2.0. These sections provide guidance that is appropriate for a .NET Core 1.x to 2.0 migration path.

3.2. Migrating from .NET Framework to .NET Core 2.1

Review the following information to migrate from the .NET Framework.

3.2.1. Migration considerations

Several technologies and APIs present in the .NET Framework are not available in .NET Core. If your application or library requires these APIs, consider finding alternatives or continue using the .NET Framework. .NET Core does not support the following technologies and APIs.

  • Desktop applications, for example, Windows Forms and Windows Presentation Foundation (WPF)
  • Windows Communication Foundation (WCF) servers (WCF clients are supported)
  • .NET remoting

Additionally, a number of .NET APIs can only be used in Microsoft Windows environments. The following list shows a few examples of these Windows-specific APIs.

  • Microsoft.Win32.Registry
  • System.AppDomains
  • System.Drawing
  • System.Security.Principal.Windows

Consider using the .NET Portability Analyzer to identify API gaps and potential replacements. For example, enter the following command to find out how much of the API used by your .NET Framework 4.6 application is supported by .NET Core 2.1.

$ dotnet /path/to/ApiPort.dll analyze -f . -r html --target '.NET Framework,Version=4.6' --target '.NET Core,Version=2.1'

Several APIs that are not supported in the out-of-the-box version of .NET Core may be available from the Microsoft.Windows.Compatibility nuget package. Be careful when using this nuget package. Some of the APIs provided (such as Microsoft.Win32.Registry) only work on Windows, making your application incompatible with Red Hat Enterprise Linux.

3.2.2. .NET Framework migration articles

Refer to the following Microsoft articles when migrating from .NET Framework.

Report a bug

Appendix A. Revision History




Les Williams

Generally available



Les Williams




Les Williams

Revised Section 1.2 to include a note about how to permanently enable rh-dotnet20



Les Williams

Revised Section 2.2 to resolve BZ 1500230; added quoting for zsh and other shells



Les Williams

Revised to include SDK 2.0 and 2.1



Les Williams

Generally available



Toby Drake

Added Chapter 3 to provide migration instructions



Toby Drake

Added steps to enable a user to get new image streams



Toby Drake

Revised Section 2.1 to include -n openshift in a command for listing .NET Core image versions. Modified the grep command to enable better search results.



Toby Drake

Added DOTNET_SSL_DIRS and DOTNET_RM_SRC to Environment Variables. Added Deploy Applications from Binary Artifacts.



Toby Drake

Changed references from docker to podman. Changed registry server to Added procedure to set up Jenkins master-slave pipeline. See Using a Jenkins Slave.



Toby Drake

Added reference to support for RHEL 8.



Les Williams

Revised environment variables section for DOTNET_INCREMENTAL and DOTNET_PACK variables

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