Cmd directive
The Dockerfile CMD instruction specifies the default command or arguments executed when a container starts, unless overridden at runtime.
Road to Kubernetes
CMD is a Dockerfile instruction that specifies the default command for a container when it starts.
- How it is used
- Configures the command a container uses by default when it starts.
- How deep it goes
- Explains direct commands and entrypoint scripts, stopping short of detailed ENTRYPOINT behavior.
- Examples
- Uses NGINX, Python with Gunicorn, and Node.js applications launched through shell scripts.
- What you can do after
- Builds Dockerfiles that start web applications directly or through configurable entrypoint scripts.
Podman in Action: Secure, rootless containers for Kubernetes, microservices, and more
A container image build directive that specifies the default command or arguments for a container.
- How it is used
- Defines the default command used when Podman launches an image without an explicit command.
- How deep it goes
- Explains defaulting, parent-image inheritance, and the distinction between build-time RUN and launch-time CMD.
- Examples
- Uses CMD /usr/bin/start.sh as a default startup command.
- What you can do after
- Apply CMD in a Containerfile to define an image's default Podman startup command.
Related concepts
- containerconfigures · A software container is an isolated execution environment that packages an application and its dependencies while sharing the host operating system kernel.
- Dockerfilepart of · A Dockerfile is a text file containing declarative instructions for building a container image and specifying its contents and runtime metadata.
- entrypoint instructionalternative to · The ENTRYPOINT instruction is a Dockerfile directive that specifies the executable or command run when a container starts.
- npm start commanduses · npm start is an npm command that runs the package manifest’s configured start script.
- run instructioncontrasts with · A Dockerfile RUN instruction executes a command during container image construction, producing filesystem changes that become part of the resulting image.
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