What are Docker init systems and why are they important?

Docker init systems handle process management inside containers: 1) Problem: PID 1 responsibilities in containers, Signal handling (SIGTERM, SIGINT), Zombie process reaping, Proper shutdown procedures, 2) Solutions: tini (lightweight init), dumb-init (simple process supervisor), s6-overlay (full init system), Docker --init flag, 3) Implementation: Dockerfile: RUN apk add --no-cache tini, ENTRYPOINT ["/sbin/tini", "--"], CMD ["myapp"], Docker run: docker run --init myapp, 4) Benefits: Proper signal forwarding to application, Zombie process cleanup, Graceful shutdown handling, Better container behavior, 5) Use cases: Applications that spawn child processes, Long-running services, Containers that need proper signal handling, 6) Example without init: Application ignores SIGTERM, docker stop waits 10 seconds then SIGKILL, Zombie processes accumulate. Example with init: tini forwards SIGTERM to application, Application shuts down gracefully, Clean process tree. Best practices: Always use init for production containers, Test signal handling, Monitor process behavior, Use minimal init systems.