DevOps Classroom notes 09/Oct/2024

Dockerfile (Containerization contd…)

CMD and ENTRYPOINT
- When a docker container starts it executes
  - Whatever is present in entrypoint and what ever has been written in CMD will be arguments to ENTRYPOINT
  - If entrypoint is present but CMD is not present in Dockerfile then whatever is written in ENTRYPOINT will be executed
  - IF ENTRYPOINT is not found and ony CMD Exists then CMD will be executed
- CMD can be overriten by passing arguments after image name in docker run command
- IF We donot write entrypoint or CMD the base images entrypoint or CMD will be considered
Your container will be in running state as long as PID1 (ENTRYPOINT + CMD) is running
Ideally anything can go in CMD or entrypoint, But in practice we execute the commands that start our application and wait till the application is executing.
Typical startup commands
- java:
  - spring boot: java -jar <jarfile path>
  - app server: if your app runs on some external server then take the base image of the app server and dont write CMD or ENTRYPOINT
- react js/angular js/vue js
  - first option: npm run start or equivalent
  - best option is to create a html site and run in nginx
- dotnet (asp.net core)
  - dotnet <dll path>
- Python
  - flask python app.py or server based startup
  - django python app.py or server based startup
  - fastapi uvicorn main:app --host 0.0.0.0 ...