tmds / build-image

Containerize .NET apps without writing Dockerfiles.

dotnet build-image

A .NET global tool to create container images from .NET projects, because life is too short to write Dockerfiles.

• The application image is built using a multi-stage build: first the application is published in an SDK image, and then the result is copied into a runtime image.
• Images are chosen that support the .NET version targetted in the project (TargetFramework).
• If a global.json file is present, it is used to determine the SDK image version.
• The image base OS can be chosen.
• Both podman and docker are supported to build the image.
• Caches NuGet packages across builds.
• The target architecture can be chosen.
• The application image runs as a non-root user.
• Supports the same properties as the SDK's built-in support to build images (https://github.com/dotnet/sdk-container-builds).

Usage

Install the tool:

$ dotnet tool install -g dotnet-build-image

Create an app:

$ dotnet new web -o web
$ cd web

Build an image:

$ dotnet build-image -t web:latest
Building image 'web:latest' from project '/tmp/web/web.csproj'.
[1/2] STEP 1/13: FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build-env
...
[2/2] STEP 9/9: ENTRYPOINT ["dotnet", "/app/web.dll"]
[2/2] COMMIT web:latest
--> 97a42d41790
Successfully tagged localhost/web:latest
97a42d41790c7d926f0152f5a86dbdbd0b5c4b6592423f6af97b7cd72c57324b

Run the image:

$ podman run -p 8080:8080 web

Options

Description:
  Build a container image from a .NET project.

Usage:
  build-image [<PROJECT>] [options]

Arguments:
  <PROJECT>  .NET project to build [default: .]

Options:
  -b, --base <base>    Flavor of the base image
  -t, --tag <tag>      Name for the built image [default: dotnet-app]
  -a, --arch <arch>    Target architecture ('x64'/'arm64'/'s390x'/'ppc64le')
                       The base image needs to support the selected architecture
  --push               After the build, push the image to the repository
  --portable           Avoid using features that make the Containerfile not portable
  --context <context>  Context directory for the build [default: .]
  --as-file <as-file>  Generates a Containerfile with the specified name
  --print              Print the Containerfile
  --version            Show version information
  -?, -h, --help       Show help and usage information

The --base option can be used to select the .NET base image. When not specified, Microsoft images from mcr.microsoft.com are used. When set to ubi, Red Hat images from registry.access.redhat.com are used. When set to another value, like alpine, the corresponding Microsoft images are used. You can also use the full image repository names, like mcr.microsoft.com/dotnet/runtime:6.0-alpine.

The options can also be specified in the .NET project file.

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    ...
    <ContainerImageName>myapp</ContainerImageName>
    <ContainerImageTag>latest</ContainerImageTag>
    <ContainerBaseImage>ubi</ContainerBaseImage>
  </PropertyGroup>

</Project>

The following properties are supported: ContainerImageTag, ContainerImageTags, ContainerImageName, ContainerRegistry, ContainerBaseImage, ContainerWorkingDirectory, ContainerImageArchitecture, ContainerSdkImage, ContainerEnvironmentVariable, ContainerLabel, ContainerPort.

Using the CI build

dotnet tool install -g dotnet-build-image --prerelease --add-source https://www.myget.org/F/tmds/api/v3/index.json