Getting Started Guide

.NET Core 2.0

Red Hat Customer Content Services

Abstract

.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 (RHEL 7) and OpenShift Container Platform via certified containers.
.NET Core offers:
  • 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 2.0 is supported on Red Hat Enterprise Linux 7 and OpenShift Container Platform versions 3.3 and later.

Chapter 1. .NET Core 2.0 on Red Hat Enterprise Linux

This Getting Started Guide describes how to install .NET Core 2.0 on Red Hat Enterprise Linux (RHEL). See Red Hat Enterprise Linux documentation for more information about Red Hat Enterprise Linux 7.

1.1. Install and Register Red Hat Enterprise Linux

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

  2. Register the system by following the appropriate steps in Registering, Unregistering, and Reregistering a System in the Red Hat Subscription Management document.

    You can also use the following command to register the system.

    $ sudo subscription-manager register
  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 2.0 and all of its dependencies.

    $ sudo yum install rh-dotnet20 -y
  2. Enable the rh-dotnet20 Software Collection environment so you can run dotnet commands in the bash shell.

    $ scl enable rh-dotnet20 bash
    Note

    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.

    Warning

    Red Hat does not recommend permanently enabling rh-dotnet20 because it may affect other programs. For example, rh-dotnet20 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 verison of libcurl. If you want to permanently enable rh-dotnet for yourself, add the following line to your ~/.bashrc file.

    source scl_source enable rh-dotnet20

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

    $ dotnet --help
    .NET Command Line Tools (2.0.0)
    Usage: dotnet [runtime-options] [path-to-application]
    Usage: dotnet [sdk-options] [command] [arguments] [command-options]
    
    path-to-application:
      The path to an application .dll file to execute.
    
    SDK commands:
      new              Initialize .NET projects.
      restore         Restore dependencies specified in the .NET project.
      run               Compiles and immediately executes a .NET project.
      build             Builds a .NET project.
      publish          Publishes a .NET project for deployment (including the runtime).
    ....

1.3. Create an Application

  1. If you want to run the classic "Hello World" test case, create the following directory.

    $ mkdir hello-world
  2. Navigate to the hello-world directory.

    $ cd hello-world
  3. Create a project.

    $ dotnet new console
    The template "Console Application" was created successfully.
    
    Processing post-creation actions...
    Running 'dotnet restore' on /home/<USER>/hello-world/hello-world.csproj...
    Restore succeeded.
  4. Pull the dependencies needed for the project.

    $ dotnet build
  5. Run the project.

    $ dotnet run
    Hello World!

1.4. Publish Applications

The .NET Core 2.0 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 dotnet Software Collection. On the other hand, SCD uses a runtime built by Microsoft and uses the global Red Hat Enterprise Linux libraries. There are known issues when using .NET Core with these libraries.

1.4.1. Publish .NET Core Applications

  1. Use the following command to publish an application using the FDD.

    $ dotnet publish -f netcoreapp2.0 -c Release
  2. If the application will only be used on RHEL, you can trim the dependencies needed for other platforms by using these commands.

    $ dotnet restore -r rhel.7-x64
    $ dotnet publish -f netcoreapp2.0 -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-dotnet20 -- 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.

    #!/bin/bash
    
    ASSEMBLY=<app>.dll
    SCL=rh-dotnet20
    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.

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

1.4.2. Publish ASP.NET Core Applications

  1. By default, ASP.NET Core 2.0 web applications are published with a dependency on a runtime store. This is a set of packages that are expected to be available on the runtime system. They are not included with the published application. RHEL does not include the ASP.NET runtime store, so the applications must be published, including all dependencies. This can be done by setting the PublishWithAspNetCoreTargetManifest property to false in the project file.

    <Project Sdk="Microsoft.NET.Sdk.Web">
      <PropertyGroup>
        <TargetFramework>netcoreapp2.0</TargetFramework>
        <PublishWithAspNetCoreTargetManifest>false</PublishWithAspNetCoreTargetManifest>
      </PropertyGroup>
      <ItemGroup>
        <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.0" />
      </ItemGroup>
    </Project>
  2. Alternatively, this property can be set when publishing the application.

    $ dotnet publish -f netcoreapp2.0 -c Release -r rhel.7-x64 --self-contained false /p:PublishWithAspNetCoreTargetManifest=false

1.5. Run Applications on Docker

This section shows how to use the dotnet/dotnet-20-runtime-rhel7 image to run your application inside a Docker container. It requires you to have the docker binary installed, the docker daemon running, and the rh-dotnet20 Software Collection enabled.

  1. Create and navigate to the following directory.

    $ mkdir mvc_runtime_example && cd mvc_runtime_example
  2. Create a new project.

    $ dotnet new mvc --no-restore
  3. Pull all dependencies.

    $ dotnet restore -r rhel.7-x64
  4. Publish the project.

    $ dotnet publish -f netcoreapp2.0 -c Release -r rhel.7-x64 \
    --self-contained false /p:PublishWithAspNetCoreTargetManifest=false
  5. Create a file called Dockerfile and add the following contents.

    $ cat > Dockerfile <<EOF
    FROM registry.access.redhat.com/dotnet/dotnet-20-runtime-rhel7
    
    ADD bin/Release/netcoreapp2.0/rhel.7-x64/publish/ .
    
    CMD ["dotnet", "mvc_runtime_example.dll"]
    EOF
  6. Build your image.

    $ sudo docker build -t dotnet-20-runtime-example .
  7. Run your image.

    $ sudo docker run -d -p8080:8080 dotnet-20-runtime-example
  8. View the result in a browser: http://127.0.0.1:8080

Report a bug

Chapter 2. .NET Core 2.0 on Red Hat OpenShift Container Platform

2.1. Install Image Streams

  1. The image stream definitions may already be part of your OpenShift Container Platform installation. Run the following command to list all dotnet versions that are available globally.

    $ oc describe is dotnet --namespace openshift
  2. If the 2.0 release is not part of the output, you can add the image streams to your installation. The image streams can be added to the current project.

    $ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/dotnet_imagestreams.json
  3. You can also add the image streams globally if you have sufficient rights.

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

2.2. Deploy Applications

  1. Run the following commands to deploy the ASP.NET Core application, which is in the app folder on the dotnetcore-2.0 branch of the redhat-developer/s2i-dotnetcore-ex GitHub repository.

    $ oc new-app --name=exampleapp dotnet:2.0~https://github.com/redhat-developer/s2i-dotnetcore-ex#dotnetcore-2.0 --build-env DOTNET_STARTUP_PROJECT=app
  2. As suggested by the output of the new-app command, you can track progress of the build using the oc logs command.

    $ oc logs -f bc/exampleapp
  3. Once the build is finished, you can see the deployed application.

    $ 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. Configuration

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

DOTNET_STARTUP_PROJECT

Used to select 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

Used to select 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_RESTORE_SOURCES

Used to specify 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.

Unset

DOTNET_NPM_TOOLS

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

Unset

DOTNET_TEST_PROJECTS

Used to specify 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.

Unset

DOTNET_CONFIGURATION

Used to run the application in Debug or Release mode. This value should be either Release or Debug.

Release

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

2.4. 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 and the .NET runtime image.
  • 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 https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/templates/dotnet-example.json
$ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/templates/dotnet-runtime-example.json
$ oc create -f https://raw.githubusercontent.com/redhat-developer/s2i-dotnetcore/master/templates/dotnet-pgsql-persistent.json

2.5. Create a Runtime Image

The .NET Core runtime image contains the files sufficient to run a .NET application, but not to build one. As such, you must provide an already published application for the runtime image. This can be a static application inside of an image that layers on top of the runtime image or a new image can be built that is fed the application from a build image. This last method is commonly referred to as chaining builds.

Deploying a build chain requires a more in-depth configuration than a simple application build. At a minimum, a build chain needs:

  • a build config for the build image
  • a build config for the runtime image
  • an inline dockerfile for the runtime image
  • a deployment config that uses the runtime image

The following elements are optional but recommended:

  • an internal image stream
  • a trigger for the build image based on the source project
  • a trigger for the runtime build based on the build image

See dotnet-runtime-example template for an example of such a configuration.

In this template, we define a *-build and a *-runtime build config. The build image builds from a GitHub project and has a trigger to rebuild automatically when the project changes or when the base image (in this case, dotnet-20-rhel7) updates.

The runtime image builds from the dotnet-20-runtime-rhel7 base image but pulls a tar.gz file from the build image that contains the build project. That is done using this source definition in the build config.

"source": {
    "dockerfile": "FROM ${DOTNET_RUNTIME_IMAGE_STREAM_TAG}\nADD app.tar.gz .",
    "images": [
        {
            "from": {
                "kind": "ImageStreamTag",
                "name": "${NAME}-build:latest"
            },
            "paths": [
                {
                    "sourcePath": "/opt/app-root/app.tar.gz",
                    "destinationDir": "."
                }
            ]
        }
    ]
}

The runtime image also has triggers to rebuild automatically when build image is updated in the projects internal image stream or when the dotnet-20-runtime-rhel7 base image updates.

There is also a deployment defined for the runtime image. A deployment is not necessary for the build image.

The use of these triggers means that any object in the chain will be rebuilt as necessary when images or code is updated.

Report a bug

Appendix A. Revision History

DateVersionAuthorChanges

08/21/2017

2.0

Les Williams

Generally available

08/30/2017

2.0

Les Williams

Revised DOTNET_STARTUP_PROJECT and DOTNET_TEST_PROJECTS entries in Section 2.3

09/13/2017

2.0

Les Williams

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

Report a bug

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