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Getting started with .NET on RHEL 9

.NET 6.0

Installing and running .NET 6.0 on RHEL 9 and OpenShift Container Platform

Red Hat Customer Content Services

Abstract

This guide describes how to install and run .NET 6.0 on RHEL 9.

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Chapter 1. Introducing .NET 6.0

.NET is a general-purpose development platform featuring automatic memory management and modern programming languages. Using .NET, you can build high-quality applications efficiently. .NET is available on Red Hat Enterprise Linux (RHEL) and OpenShift Container Platform through certified containers.

.NET 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 on RHEL and OpenShift Container Platform.
  • The capacity to more easily develop new .NET workloads on Microsoft Windows. You can deploy and run your applications on either RHEL 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 6.0 is supported on RHEL 7, RHEL 8, RHEL 9, and OpenShift Container Platform versions 3.11 and later.

Chapter 2. Installing .NET 6.0

.NET 6.0 is included in the AppStream repositories for RHEL 9. The AppStream repositories are enabled by default on RHEL 9 systems.

You can install the .NET 6.0 runtime with the latest 6.0 Software Development Kit (SDK). When a newer SDK becomes available for .NET 6.0, you can install it by running sudo yum upgrade.

Prerequisites

Procedure

  • Install .NET 6.0 and all of its dependencies: 

    $ sudo yum install dotnet-sdk-6.0 -y

Verification steps

  • Verify the installation: 

    $ dotnet --info

    The output returns the relevant information about the .NET installation and the environment.

Chapter 3. Creating an application using .NET 6.0

Learn how to create a C# hello-world application.

Procedure

  1. Create a new Console application in a directory called my-app: 

    $ dotnet new console --output my-app

    The output returns: 

    The template "Console Application" was created successfully.

Processing post-creation actions...
Running 'dotnet restore' on my-app/my-app.csproj...
  Determining projects to restore...
  Restored /home/username/my-app/my-app.csproj (in 67 ms).
Restore succeeded.

    A simple Hello World console application is created from a template. The application is stored in the specified my-app directory.

Verification steps

  • Run the project: 

    $ dotnet run --project my-app

    The output returns: 

    Hello World!

Chapter 4. Publishing applications with .NET 6.0

.NET 6.0 applications can be published to use a shared system-wide version of .NET or to include .NET.

The following methods exist for publishing .NET 6.0 applications:

  • Single-file application - The application is self-contained and can be deployed as a single executable with all dependent files contained in a single binary.
Note

Single-file application deployment is not available on IBM Z and LinuxONE.

  • Framework-dependent deployment (FDD) - The application uses a shared system-wide version of .NET.
Note

When publishing an application for RHEL, Red Hat recommends using FDD, because it ensures that the application is using an up-to-date version of .NET, built by Red Hat, that uses a set of native dependencies.

  • Self-contained deployment (SCD) - The application includes .NET. This method uses a runtime built by Microsoft.
Note

SCD is not available on IBM Z and LinuxONE.

Prerequisites

4.1. Publishing .NET applications

The following procedure outlines how to publish a framework-dependent application.

Procedure

  1. Publish the framework-dependent application: 

    $ dotnet publish my-app -f net6.0 -c Release

    Replace my-app with the name of the application you want to publish.

  2. Optional: If the application is for RHEL only, trim out the dependencies needed for other platforms: 

    $ dotnet publish my-app -f net6.0 -c Release -r rhel.9-architecture --self-contained false

    • Replace architecture based on the platform you are using:

      • For Intel: x64
      • For IBM Z and LinuxONE: s390x
      • For 64-bit Arm: arm64

Chapter 5. Running .NET 6.0 applications in containers

Use the ubi8/dotnet-60-runtime image to run a precompiled application inside a Linux container.

Prerequisites

  • Preconfigured containers.

    The following example uses podman.

Procedure

  1. Optional: If you are in another project’s directory and do not wish to create a nested project, return to the parent directory of the project: 

    # cd ..

  2. Create a new MVC project in a directory called mvc_runtime_example: 

    $ dotnet new mvc --output mvc_runtime_example

  3. Publish the project: 

    $ dotnet publish mvc_runtime_example -f net6.0 -c Release

  4. Create the Dockerfile: 

    $ cat > Dockerfile <<EOF
FROM registry.access.redhat.com/ubi8/dotnet-60-runtime

ADD bin/Release/net6.0/publish/ .

CMD ["dotnet", "mvc_runtime_example.dll"]
EOF

  5. Build your image: 

    $ podman build -t dotnet-60-runtime-example .

  6. Run your image: 

    $ podman run -d -p8080:8080 dotnet-60-runtime-example

Verification steps

  • View the application running in the container: 

    $ xdg-open http://127.0.0.1:8080

Chapter 6. Using .NET 6.0 on OpenShift Container Platform

6.1. Overview

NET images are added to OpenShift by importing imagestream definitions from s2i-dotnetcore.

The imagestream definitions includes the dotnet imagestream which contains sdk images for different supported versions of .NET. .NET Life Cycle provides an up-to-date overview of supported versions.

VersionTagAlias

.NET Core 3.1

dotnet:3.1-el7

dotnet:3.1

dotnet:3.1-ubi8

 

.NET 5

dotnet:5.0-ubi8

dotnet:5.0

.NET 6

dotnet:6.0-ubi8

dotnet:6.0

The sdk images have corresponding runtime images which are defined under the dotnet-runtime imagestream.

The container images work across different versions of Red Hat Enterprise Linux and OpenShift.

The RHEL7-based (suffix -el7) are hosted on the registry.redhat.io image repository. Authentication is required to pull these images. These credentials are configured by adding a pull secret to the OpenShift namespace.

The UBI-8 based images (suffix -ubi8) are hosted on the registry.access.redhat.com and do not require authentication.

6.2. Installing .NET image streams

To install .NET image streams, use image stream definitions from s2i-dotnetcore with the OpenShift Client (oc) binary. Image streams can be installed from Linux, Mac, and Windows. A script enables you to install, update or remove the image streams.

You can define .NET image streams in the global openshift namespace or locally in a project namespace. Sufficient permissions are required to update the openshift namespace definitions.

6.2.1. Installing image streams using OpenShift Client

You can use OpenShift Client (oc) to install .NET image streams.

Prerequisites

Procedure

  1. List the available .NET image streams: 

    $ oc describe is dotnet

    The output shows installed images. If no images are installed, the Error from server (NotFound) message is displayed.

    • If the Error from server (NotFound) message is displayed:

      • Install the .NET image streams: 

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

    • If the Error from server (NotFound) message is not displayed:

      • Include newer versions of existing .NET image streams: 

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

6.2.2. Installing image streams on Linux and macOS

You can use this script to install, upgrade, or remove the image streams on Linux and macOS.

Procedure

  1. Download the script.

    1. On Linux use: 

      $ wget https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh

    2. On Mac use: 

      $ curl https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.sh -o install-imagestreams.sh

  2. Make the script executable: 

    $ chmod +x install-imagestreams.sh

  3. Log in to the OpenShift cluster: 

    $ oc login

  4. Install image streams and add a pull secret for authentication against the registry.redhat.io: 

    ./install-imagestreams.sh --os rhel [--user subscription_username --password subscription_password]

    Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.

    If the pull secret is already present, the --user and --password arguments are ignored.

Additional information

  • ./install-imagestreams.sh --help

6.2.3. Installing image streams on Windows

You can use this script to install, upgrade, or remove the image streams on Windows.

Procedure

  1. Download the script. 

    Invoke-WebRequest https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/install-imagestreams.ps1 -UseBasicParsing -OutFile install-imagestreams.ps1

  2. Log in to the OpenShift cluster: 

    $ oc login

  3. Install image streams and add a pull secret for authentication against the registry.redhat.io: 

    .\install-imagestreams.ps1 --OS rhel [-User subscription_username -Password subscription_password]

    Replace subscription_username with the name of the user, and replace subscription_password with the user’s password. The credentials may be omitted if you do not plan to use the RHEL7-based images.

    If the pull secret is already present, the -User and -Password arguments are ignored.

Note

The PowerShell ExecutionPolicy may prohibit executing this script. To relax the policy, run Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass -Force.

Additional information

  • Get-Help .\install-imagestreams.ps1

6.3. Deploying applications from source using oc

The following example demonstrates how to deploy the example-app application using oc, which is in the app folder on the {dotnet-branch} branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository:

Procedure

  1. Create a new OpenShift project: 

    $ oc new-project sample-project

  2. Add the ASP.NET Core application: 

    $ oc new-app --name=example-app 'dotnet:6.0-ubi8~https://github.com/redhat-developer/s2i-dotnetcore-ex#{dotnet-branch}' --build-env DOTNET_STARTUP_PROJECT=app

  3. Track the progress of the build: 

    $ oc logs -f bc/example-app

  4. View the deployed application once the build is finished: 

    $ oc logs -f dc/example-app

    The application is now accessible within the project.

  5. Optional: Make the project accessible externally: 

    $ oc expose svc/example-app

  6. Obtain the shareable URL: 

    $ oc get routes

6.4. Deploying applications from binary artifacts using oc

You can use .NET Source-to-Image (S2I) builder image to build applications using binary artifacts that you provide.

Prerequisites

  1. Published application.

    For more information, see Publishing applications with .NET 6.0.

Procedure

  1. Create a new binary build: 

    $ oc new-build --name=my-web-app dotnet:6.0-ubi8 --binary=true

  2. Start the build and specify the path to the binary artifacts on your local machine: 

    $ oc start-build my-web-app --from-dir=bin/Release/net6.0/publish

  3. Create a new application: 

    $ oc new-app my-web-app

6.5. Environment variables for .NET 6.0

The .NET images support several environment variables to control the build behavior of your .NET application. You can set these variables as part of the build configuration, or add them to the .s2i/environment file in the application source code repository.

Variable NameDescriptionDefault

DOTNET_STARTUP_PROJECT

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

.

DOTNET_ASSEMBLY_NAME

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

DOTNET_PUBLISH_READYTORUN

When set to true, the application will be compiled ahead of time. This reduces startup time by reducing the amount of work the JIT needs to perform when the application is loading.

false

DOTNET_RESTORE_SOURCES

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. This variable cannot be combined with DOTNET_RESTORE_CONFIGFILE.

 

DOTNET_RESTORE_CONFIGFILE

Specifies a NuGet.Config file to be used for restore operations. This variable cannot be combined with DOTNET_RESTORE_SOURCES.

 

DOTNET_TOOLS

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>.

 

DOTNET_NPM_TOOLS

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

 

DOTNET_TEST_PROJECTS

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.

 

DOTNET_CONFIGURATION

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

Release

DOTNET_VERBOSITY

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]).

 

HTTP_PROXY, HTTPS_PROXY

Configures the HTTP or HTTPS proxy used when building and running the application, respectively.

 

DOTNET_RM_SRC

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

 

DOTNET_SSL_DIRS

Specifies a list of folders or 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).

 

NPM_MIRROR

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

 

ASPNETCORE_URLS

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.

http://*:8080

DOTNET_RESTORE_DISABLE_PARALLEL

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.

false

DOTNET_INCREMENTAL

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

false

DOTNET_PACK

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

 

6.6. Creating the MVC sample application

s2i-dotnetcore-ex is the default Model, View, Controller (MVC) template application for .NET.

This application is used as the example application by the .NET S2I image and can be created directly from the OpenShift UI using the Try Example link.

The application can also be created with the OpenShift client binary (oc).

Procedure

To create the sample application using oc:

  1. Add the .NET application: 

    $ oc new-app dotnet:6.0-ubi8~https://github.com/redhat-developer/s2i-dotnetcore-ex#{dotnet-branch} --context-dir=app

  2. Make the application accessible externally: 

    $ oc expose service s2i-dotnetcore-ex

  3. Obtain the sharable URL: 

    $ oc get route s2i-dotnetcore-ex

Additional resources

6.7. Creating the CRUD sample application

s2i-dotnetcore-persistent-ex is a simple Create, Read, Update, Delete (CRUD) .NET web application that stores data in a PostgreSQL database.

Procedure

To create the sample application using oc:

  1. Add the database: 

    $ oc new-app postgresql-ephemeral

  2. Add the .NET application: 

    $ oc new-app dotnet:6.0-ubi8~https://github.com/redhat-developer/s2i-dotnetcore-persistent-ex#{dotnet-branch} --context-dir app

  3. Add environment variables from the postgresql secret and database service name environment variable: 

    $ oc set env dc/s2i-dotnetcore-persistent-ex --from=secret/postgresql -e database-service=postgresql

  4. Make the application accessible externally: 

    $ oc expose service s2i-dotnetcore-persistent-ex

  5. Obtain the sharable URL: 

    $ oc get route s2i-dotnetcore-persistent-ex

Additional resources

Chapter 7. Migration from previous versions of .NET

7.1. Migration from previous versions of .NET

Microsoft provides instructions for migrating from most previous versions of .NET Core.

If you are using a version of .NET that is no longer supported or want to migrate to a newer .NET version to expand functionality, see the following articles:

Note

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.

7.2. Porting from .NET Framework

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

Several technologies and APIs present in the .NET Framework are not available in .NET Core and .NET. If your application or library requires these APIs, consider finding alternatives or continue using the .NET Framework. .NET Core and .NET do 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, several .NET APIs can only be used in Microsoft Windows environments. The following list shows examples of these Windows-specific APIs:

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

Several APIs that are not supported in the default version of .NET 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.

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