Docker 1 – Explain basic Docker file

FROM mcr.microsoft.com/dotnet/aspnet:6.0 AS base

WORKDIR /app

EXPOSE 80

FROM mcr.microsoft.com/dotnet/sdk:6.0 AS build

WORKDIR /src

COPY . .

RUN dotnet publish -c Release -o /app/publish

FROM base AS final

WORKDIR /app

COPY –from=build /app/publish .

ENTRYPOINT [“dotnet”, “YourApp.dll”]

This Dockerfile is a multi-stage build for a .NET 6.0 ASP.NET application

🧠 Layman’s Explanation:

Imagine you’re baking a cake:

1. You prepare the kitchen (base image).
2. You mix and bake the cake (build stage).
3. You serve the cake on a clean plate (final stage).

This Dockerfile does the same:

• It sets up the environment.
• Builds the app.
• Packages only the final result into a clean container.

💻 Technical Breakdown:

🔹 Stage 1: Base Image

• Uses the ASP.NET runtime image (no SDK).
• Sets working directory to /app.
• Exposes port 80 for incoming traffic.

This is the lightweight runtime environment where the app will eventually run.

Stage 2: Build Image

• Uses the SDK image (includes compilers and tools).
• Copies your source code into the container.
• Runs dotnet publish to compile and prepare the app for deployment.

This is the build kitchen — it compiles the code and prepares the final dish.

Stage 3: Final Image

• Starts from the base image again (clean runtime).
• Copies the published output from the build stage.
• Sets the entry point to run your app.

This is the serving plate — clean, optimized, and ready to run.

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✅ Benefits of Multi-Stage Build:

• Keeps the final image small and secure.
• Avoids shipping unnecessary build tools.
• Separates build and runtime environments.