What is the difference between CMD and RUN in Containerfile/Dockerfile?

RUN lets you execute commands inside of your Docker image. These commands get executed once at build time and get written into your Docker image as a new layer. CMD is the command the container executes by default when you launch the built image. A Containerfile/Dockerfile can only have one CMD. You could say that CMD is a Docker run-time operation, meaning it’s not something that gets executed at build time. It happens when you run an image. A running image is called a container.