Fix: Docker Container Exiting Immediately

!Symptoms

• Container starts and immediately exits (status 'Exited')
• docker run returns immediately without keeping the container alive
• docker ps shows nothing but docker ps -a shows exited containers
• docker logs shows the application error or nothing at all

?Root Causes

• Entrypoint or CMD process exits (no foreground process)
• Application crashes on startup due to configuration error
• Missing environment variables required by the application
• Incorrect working directory or file permissions inside the container
• Using shell form CMD that exits when the shell exits

#Diagnosis Steps

1. 1Check container logs: `docker logs <container-id>`
2. 2Check exit code: `docker inspect <container-id> --format='{{.State.ExitCode}}'`
3. 3Inspect the entrypoint: `docker inspect <image> --format='{{.Config.Entrypoint}} {{.Config.Cmd}}'`
4. 4Run interactively to debug: `docker run -it --entrypoint /bin/sh <image>`
5. 5Check if all required env vars are set in your docker run command

>Fix

1. 1Ensure CMD runs a foreground process (not a daemon/background process)
2. 2Use exec form for CMD: `CMD ["node", "server.js"]` not `CMD node server.js &`
3. 3Pass all required environment variables with -e flags or --env-file
4. 4Fix file permissions: add proper USER and chmod in Dockerfile
5. 5If debugging, keep alive temporarily: `docker run -it <image> /bin/sh`

*Prevention

• Always test Docker images locally before deploying
• Use HEALTHCHECK in Dockerfile to detect startup failures
• Document all required environment variables in the README or .env.example
• Use docker-compose for consistent environment variable management
• Add proper signal handling (SIGTERM) in your application for graceful shutdown

Related Error Messages