Docker

Core Principles

1. Multi-stage builds always — Separate build and runtime stages. Build in the SDK image, run in the ASP.NET runtime image.
2. Non-root by default — .NET container images support USER app by default since .NET 8. Never run as root in production.
3. Layer caching matters — Copy .csproj files and restore before copying source code. This caches NuGet dependencies across builds.
4. Health probes at the orchestrator level — Expose a /health/live endpoint and let Kubernetes/Compose probe it. Chiseled and default aspnet images have no shell or curl, so in-image HEALTHCHECK commands have nothing to run with.

Patterns

Multi-Stage Dockerfile for Web API

# Stage 1: Build
FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
WORKDIR /src