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@@ -950,6 +950,29 @@ If you then run `docker stop test`, the container will not exit cleanly - the
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user 0m 0.04s
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sys 0m 0.03s
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+### Understand how CMD and ENTRYPOINT interact
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+
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+Both `CMD` and `ENTRYPOINT` instructions define what command gets executed when running a container.
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+There are few rules that describe their co-operation.
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+
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+1. Dockerfile should specify at least one of `CMD` or `ENTRYPOINT` commands.
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+
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+2. `ENTRYPOINT` should be defined when using the container as an executable.
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+
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+3. `CMD` should be used as a way of defining default arguments for an `ENTRYPOINT` command
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+or for executing an ad-hoc command in a container.
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+
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+4. `CMD` will be overridden when running the container with alternative arguments.
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+
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+The table below shows what command is executed for different `ENTRYPOINT` / `CMD` combinations:
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+
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+| | No ENTRYPOINT | ENTRYPOINT exec_entry p1_entry | ENTRYPOINT ["exec_entry", "p1_entry"] |
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+|--------------------------------|----------------------------|-----------------------------------------------------------|------------------------------------------------|
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+| **No CMD** | *error, not allowed* | /bin/sh -c exec_entry p1_entry | exec_entry p1_entry |
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+| **CMD ["exec_cmd", "p1_cmd"]** | exec_cmd p1_cmd | /bin/sh -c exec_entry p1_entry exec_cmd p1_cmd | exec_entry p1_entry exec_cmd p1_cmd |
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+| **CMD ["p1_cmd", "p2_cmd"]** | p1_cmd p2_cmd | /bin/sh -c exec_entry p1_entry p1_cmd p2_cmd | exec_entry p1_entry p1_cmd p2_cmd |
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+| **CMD exec_cmd p1_cmd** | /bin/sh -c exec_cmd p1_cmd | /bin/sh -c exec_entry p1_entry /bin/sh -c exec_cmd p1_cmd | exec_entry p1_entry /bin/sh -c exec_cmd p1_cmd |
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+
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## VOLUME
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VOLUME ["/data"]
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Sebastiaan van Stijn