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SKILL.md
npx skills add github/awesome-copilot --skill containerize-aspnetcore
Containerize an ASP.NET Core project by creating Dockerfile and .dockerfile files customized for the project.
npx skills add github/awesome-copilot --skill containerize-aspnetcore
Containerize the ASP.NET Core (.NET) project specified in the settings below, focusing exclusively on changes required for the application to run in a Linux Docker container. Containerization should consider all settings specified here.
Abide by best practices for containerizing .NET Core applications, ensuring that the container is optimized for performance, security, and maintainability.
This section of the prompt contains the specific settings and configurations required for containerizing the ASP.NET Core application. Prior to running this prompt, ensure that the settings are filled out with the necessary information. Note that in many cases, only the first few settings are required. Later settings can be left as defaults if they do not apply to the project being containerized.
Any settings that are not specified will be set to default values. The default values are provided in [square brackets].
Project to containerize:
[ProjectName (provide path to .csproj file)].NET version to use:
[8.0 or 9.0 (Default 8.0)]Linux distribution to use:
[debian, alpine, ubuntu, chiseled, or Azure Linux (mariner) (Default debian)]Custom base image for the build stage of the Docker image ("None" to use standard Microsoft base image):
[Specify base image to use for build stage (Default None)]Custom base image for the run stage of the Docker image ("None" to use standard Microsoft base image):
[Specify base image to use for run stage (Default None)]Ports that must be exposed in the container image:
[e.g., 8080][List any additional ports, or "None"]User account the container should run as:
[User account, or default to "$APP_UID"]Application URL configuration:
[Specify ASPNETCORE_URLS, or default to "http://+:8080"]Custom build steps that must be performed before building the container image:
[List any specific build steps, or "None"]Custom build steps that must be performed after building the container image:
[List any specific build steps, or "None"]NuGet package sources that must be configured:
[List any private NuGet feeds with authentication details, or "None"]System packages that must be installed in the container image:
[Package names for the chosen Linux distribution, or "None"]Native libraries that must be copied to the container image:
[Library names and paths, or "None"]Additional .NET tools that must be installed:
[Tool names and versions, or "None"][Variable names and values, or "Use defaults"]Files/directories that need to be copied to the container image:
[Paths relative to project root, or "None"][Container paths, or "Not applicable"]Files/directories to exclude from containerization:
[Paths to exclude, or "None"]Volume mount points that should be configured:
[Volume paths for persistent data, or "None"].dockerignore file (.dockerignore will already have common defaults; these are additional patterns):
[List any additional patterns, or "None"]Health check endpoint:
[Health check URL path, or "None"]Health check interval and timeout:
[Interval and timeout values, or "Use defaults"]Other instructions that must be followed to containerize the project:
[Specific requirements, or "None"]Known issues to address:
[Describe any known issues, or "None"]progress.md file to track changes with check marksTargetFramework element$APP_UID))
$APP_UID variable to specify the user account..dockerignore file in the root of the project directory to exclude unnecessary files from the Docker image. The .dockerignore file MUST include at least the following elements as well as additional patterns as specified in the containerization settings:
Confirm that Docker build succeeds once the Dockerfile is completed. Use the following command to build the Docker image:
If the build fails, review the error messages and make necessary adjustments to the Dockerfile or project configuration. Report success/failure.
Maintain a progress.md file with the following structure:
Do not pause for confirmation between steps. Continue methodically until the application has been containerized and Docker build succeeds.
YOU ARE NOT DONE UNTIL ALL CHECKBOXES ARE MARKED! This includes building the Docker image successfully and addressing any issues that arise during the build process.
An example Dockerfile for an ASP.NET Core (.NET) application using a Linux base image.
Note: Customize this template based on the specific requirements in containerization settings.
When adapting this example Dockerfile:
YourProject.csproj, YourProject.dll, etc. with your actual project namesFor smaller image sizes, you can use Alpine Linux:
For minimal attack surface, consider using chiseled images:
For Azure-optimized containers:
AS stage-name syntax gives each stage a name--from=stage-name to copy files from a previous stagefinal stage is the one that becomes the final container imagelatest# ============================================================
# Stage 1: Build and publish the application
# ============================================================
# Base Image - Select the appropriate .NET SDK version and Linux distribution
# Possible tags include:
# - 8.0-bookworm-slim (Debian 12)
# - 8.0-noble (Ubuntu 24.04)
# - 8.0-alpine (Alpine Linux)
# - 9.0-bookworm-slim (Debian 12)
# - 9.0-noble (Ubuntu 24.04)
# - 9.0-alpine (Alpine Linux)
# Uses the .NET SDK image for building the application
FROM mcr.microsoft.com/dotnet/sdk:8.0-bookworm-slim AS build
ARG BUILD_CONFIGURATION=Release
WORKDIR /src
# Copy project files first for better caching
COPY ["YourProject/YourProject.csproj", "YourProject/"]
COPY ["YourOtherProject/YourOtherProject.csproj", "YourOtherProject/"]
# Copy NuGet configuration if it exists
COPY ["NuGet.config", "."]
# Restore NuGet packages
RUN dotnet restore "YourProject/YourProject.csproj"
# Copy source code
COPY . .
# Perform custom pre-build steps here, if needed
# RUN echo "Running pre-build steps..."
# Build and publish the application
WORKDIR "/src/YourProject"
RUN dotnet build "YourProject.csproj" -c $BUILD_CONFIGURATION -o /app/build
# Publish the application
RUN dotnet publish "YourProject.csproj" -c $BUILD_CONFIGURATION -o /app/publish /p:UseAppHost=false
# Perform custom post-build steps here, if needed
# RUN echo "Running post-build steps..."
# ============================================================
# Stage 2: Final runtime image
# ============================================================
# Base Image - Select the appropriate .NET runtime version and Linux distribution
# Possible tags include:
# - 8.0-bookworm-slim (Debian 12)
# - 8.0-noble (Ubuntu 24.04)
# - 8.0-alpine (Alpine Linux)
# - 8.0-noble-chiseled (Ubuntu 24.04 Chiseled)
# - 8.0-azurelinux3.0 (Azure Linux)
# - 9.0-bookworm-slim (Debian 12)
# - 9.0-noble (Ubuntu 24.04)
# - 9.0-alpine (Alpine Linux)
# - 9.0-noble-chiseled (Ubuntu 24.04 Chiseled)
# - 9.0-azurelinux3.0 (Azure Linux)
# Uses the .NET runtime image for running the application
FROM mcr.microsoft.com/dotnet/aspnet:8.0-bookworm-slim AS final
# Install system packages if needed (uncomment and modify as needed)
# RUN apt-get update && apt-get install -y \
# curl \
# wget \
# ca-certificates \
# libgdiplus \
# && rm -rf /var/lib/apt/lists/*
# Install additional .NET tools if needed (uncomment and modify as needed)
# RUN dotnet tool install --global dotnet-ef --version 8.0.0
# ENV PATH="$PATH:/root/.dotnet/tools"
WORKDIR /app
# Copy published application from build stage
COPY --from=build /app/publish .
# Copy additional files if needed (uncomment and modify as needed)
# COPY ./config/appsettings.Production.json .
# COPY ./certificates/ ./certificates/
# Set environment variables
ENV ASPNETCORE_ENVIRONMENT=Production
ENV ASPNETCORE_URLS=http://+:8080
# Add custom environment variables if needed (uncomment and modify as needed)
# ENV CONNECTIONSTRINGS__DEFAULTCONNECTION="your-connection-string"
# ENV FEATURE_FLAG_ENABLED=true
# Configure SSL/TLS certificates if needed (uncomment and modify as needed)
# ENV ASPNETCORE_Kestrel__Certificates__Default__Path=/app/certificates/app.pfx
# ENV ASPNETCORE_Kestrel__Certificates__Default__Password=your_password
# Expose the port the application listens on
EXPOSE 8080
# EXPOSE 8081 # Uncomment if using HTTPS
# Install curl for health checks if not already present
RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/*
# Configure health check
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
CMD curl -f http://localhost:8080/health || exit 1
# Create volumes for persistent data if needed (uncomment and modify as needed)
# VOLUME ["/app/data", "/app/logs"]
# Switch to non-root user for security
USER $APP_UID
# Set the entry point for the application
ENTRYPOINT ["dotnet", "YourProject.dll"]FROM mcr.microsoft.com/dotnet/sdk:8.0-alpine AS build
# ... build steps ...
FROM mcr.microsoft.com/dotnet/aspnet:8.0-alpine AS final
# Install packages using apk
RUN apk update && apk add --no-cache curl ca-certificatesFROM mcr.microsoft.com/dotnet/aspnet:8.0-jammy-chiseled AS final
# Note: Chiseled images have minimal packages, so you may need to use a different base for additional dependenciesFROM mcr.microsoft.com/dotnet/aspnet:8.0-azurelinux3.0 AS final
# Install packages using tdnf
RUN tdnf update -y && tdnf install -y curl ca-certificates && tdnf clean all