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feat(docker): add exec notes & rework CMD and ENTRYPOINT notes

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Marcello 2023-06-26 11:38:33 +02:00
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docs/containers/docker.md
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@ -86,12 +86,13 @@ docker container ls -a|--all # list of all containers, running and exited
docker container rm <container> # remove one or more containers
docker container prune # remove stopped containers
docker container inspect <container> # full details about a container
docker container logs <container> # see container logs
docker container stop <container> # stop a running container
docker container start <container> # start a stopped container
docker container exec <container> <command> # exec a command inside a container
```
### [`docker image`](https://docs.docker.com/engine/reference/commandline/image/)
@ -146,41 +147,12 @@ CMD <executable> <arg1> <arg2>
ENTRYPOINT <executable> <arg1> <arg2>
```
### `CMD`
### `CMD` vs `ENTRYPOINT`
Used to provide all the default scenarios which can be overridden.
`CMD` is used to provide all the default scenarios which can be overridden. _Anything_ defined in CMD can be overridden by passing arguments in `docker run` command.
#### Default executable
This instructions is used to define a default executable for a container to execute.
If you want to create a generic docker image, where users can pass any supported command to be executed on container invocation, then this instruction is the one to use.
Entrypoint instruction should not be defined in Dockerfile for this use case.
```docker
CMD ["executable", "arg1", "arg2"]
```
#### Default arguments
For this use case, we don’t specify executable in this instruction at all, but simply define some arguments which are used as default/additional
arguments for executable defined in the entrypoint instruction.
Thus, entrypoint instruction is required in dockerfile for this use case to define an executable.
```docker
ENTRYPOINT ["executable"]
CMD ["arg1", "arg2"]
```
> **Note**: Anything defined in CMD can be overridden by passing arguments in `docker run` command.
### `ENTRYPOINT`
Used to define specific executable and arguments to be executed during container invocation which cannot be overridden.
This is used to constraint the user to execute anything else. User can however define arguments to be passed in the executable by adding them in the `docker run` command.
`ENTRYPOINT` is used to define a specific executable (and it's arguments) to be executed during container invocation which cannot be overridden.
The user can however define arguments to be passed in the executable by adding them in the `docker run` command.
## [Docker Multi-Stage Build](https://docs.docker.com/develop/develop-images/multistage-build/)