How do ENTRYPOINT and CMD instructions interact?
Experience Level: Senior
Tags: Docker
Answer
Both ENTRYPOINT and CMD instructions define what command gets executed when running a container. There are few rules that describe their co-operation.
- Dockerfile should specify at least one of CMD or ENTRYPOINT commands.
- ENTRYPOINT should be defined when using the container as an executable.
- CMD should be used as a way of defining default arguments for an ENTRYPOINT command or for executing an ad-hoc command in a container.
- CMD will be overridden when running the container with alternative arguments.
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