/container-publish

name: container-publish
description: >
  Dockerfile-less containerization using the .NET 10 SDK container publishing
  feature. Covers MSBuild properties, chiseled images, multi-arch builds, and
  registry publishing — all without writing a Dockerfile.
  Load this skill when the user wants to containerize without a Dockerfile, or
  mentions "dotnet publish container", "PublishContainer", "ContainerRepository",
  "ContainerFamily", "chiseled", "distroless", "container publish", "SDK
  container", "no Dockerfile", or "containerize without Docker".

Container Publishing (No Dockerfile)

Core Principles

1. **No Dockerfile needed** — The .NET 10 SDK builds OCI-compliant container images directly from `dotnet publish /t:PublishContainer`. No Dockerfile to write or maintain. 2. **Chiseled images for production** — Use `noble-chiseled` base images: no shell, no package manager, 7 Linux components vs 100+. Smallest attack surface. 3. **Non-root by default** — .NET 10 container images run as the `app` user automatically. Never override to root in production. 4. **Configuration in the .csproj** — All container settings are MSBuild properties, versioned with your project. No separate files to drift.

Patterns

Minimal Container Publish

No project file changes needed. Just publish:

dotnet publish /t:PublishContainer --os linux --arch x64

This creates a container image in your local Docker daemon using the default `aspnet:10.0` base image.

Production-Ready .csproj Configuration

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

  <PropertyGroup>
    <TargetFramework>net10.0</TargetFramework>
    <ContainerRepository>mycompany/myapp-api</ContainerRepository>
    <ContainerFamily>noble-chiseled</ContainerFamily>
  </PropertyGroup>

  <ItemGroup>
    <ContainerPort Include="8080" Type="tcp" />
    <ContainerEnvironmentVariable Include="ASPNETCORE_HTTP_PORTS" Value="8080" />
    <ContainerEnvironmentVariable Include="DOTNET_EnableDiagnostics" Value="0" />
    <ContainerLabel Include="org.opencontainers.image.vendor" Value="MyCompany" />
  </ItemGroup>

</Project>

Publishing to a Registry

Authenticate with `docker login` first, then specify the registry:

# GitHub Container Registry
docker login ghcr.io
dotnet publish /t:PublishContainer --os linux --arch x64 \
    -p ContainerRegistry=ghcr.io \
    -p ContainerImageTag=1.0.0

# Azure Container Registry
az acr login --name myregistry
dotnet publish /t:PublishContainer --os linux --arch x64 \
    -p ContainerRegistry=myregistry.azurecr.io

# Docker Hub (requires username prefix in repository)
dotnet publish /t:PublishContainer --os linux --arch x64 \
    -p ContainerRegistry=docker.io \
    -p ContainerRepository=myuser/myapp

Multi-Architecture Images

Build images for multiple platforms with a single publish:

<PropertyGroup>
    <RuntimeIdentifiers>linux-x64;linux-arm64</RuntimeIdentifiers>
    <ContainerRuntimeIdentifiers>linux-x64;linux-arm64</ContainerRuntimeIdentifiers>
</PropertyGroup>

dotnet publish /t:PublishContainer

This produces an OCI Image Index — registries serve the correct architecture automatically.

Multiple Tags

# Bash — note the quoting for semicolons
dotnet publish /t:PublishContainer --os linux --arch x64 \
    -p ContainerImageTags='"1.0.0;latest"'

Or in the project file:

<ContainerImageTags>1.0.0;latest</ContainerImageTags>

Save as Tarball (No Docker Required)

No container runtime needed on the build machine. Useful for CI scanning:

dotnet publish /t:PublishContainer --os linux --arch x64 \
    -p ContainerArchiveOutputPath=./images/myapp.tar.gz

# Scan with Trivy before pushing
trivy image --input ./images/myapp.tar.gz

Chiseled Image Variants

| ContainerFamily | Use Case | Shell | Size | |----------------|----------|-------|------| | *(default)* | General purpose (Debian) | Yes | ~220 MB | | `noble-chiseled` | Production (no shell) | No | ~110 MB | | `noble-chiseled-extra` | Production with localization (ICU) | No | ~120 MB | | `alpine` | Small size, has shell | Yes | ~112 MB |

<!-- Standard chiseled (InvariantGlobalization=true) -->
<ContainerFamily>noble-chiseled</ContainerFamily>

<!-- Chiseled with ICU for localization -->
<ContainerFamily>noble-chiseled-extra</ContainerFamily>

For Native AOT, the SDK auto-selects `chiseled-aot`:

<PublishAot>true</PublishAot>
<!-- SDK picks runtime-deps:10.0-noble-chiseled-aot automatically -->

CI/CD with GitHub Actions

jobs:
  publish:
    runs-on: ubuntu-latest
    permissions:
      packages: write
    steps:
      - uses: actions/checkout@v5
      - uses: actions/setup-dotnet@v5
        with:
          dotnet-version: '10.0.x'
      - uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - run: |
          dotnet publish src/MyApp.Api/MyApp.Api.csproj \
            /t:PublishContainer --os linux --arch x64 \
            -p ContainerRegistry=ghcr.io \
            -p ContainerRepository=${{ github.repository_owner }}/myapp \
            -p ContainerImageTag=${{ github.sha }}

Anti-patterns

Don't Use the Deprecated Property Names

<!-- BAD — ContainerImageName is deprecated -->
<ContainerImageName>myapp</ContainerImageName>

<!-- GOOD — use ContainerRepository -->
<ContainerRepository>myapp</ContainerRepository>

Don't Use PublishProfile=DefaultContainer

# BAD — old approach, inconsistent across project types
dotnet publish -p:PublishProfile=DefaultContainer

# GOOD — use the MSBuild target directly
dotnet publish /t:PublishContainer

Don't Forget to Target Linux

# BAD on Windows — may produce a Windows container
dotnet publish /t:PublishContainer

# GOOD — explicitly target Linux
dotnet publish /t:PublishContainer --os linux --arch x64

Don't S