CMD vs ENTRYPOINT in a Dockerfile

常常忘記，很粗略的筆記一下
經同事說明

根據：

• https://stackoverflow.com/questions/21553353/what-is-the-difference-between-cmd-and-entrypoint-in-a-dockerfile
• https://docs.docker.com/v17.09/engine/reference/builder/

CMD

• The CMD specifies arguments that will be fed to the ENTRYPOINT.
• There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect.

ENTRYPOINT

• The ENTRYPOINT specifies a command that will always be executed when the container starts.
• An ENTRYPOINT allows you to configure a container that will run as an executable.

應該是這樣子：

• 一個 Dockerfile 內只能有一個 CMD，如果有多，生效會是最後一個 CMD
• CMD 會被當成 ENTRYPOINT 參數
• ENTRYPOINT 預設是 /bin/sh -c
• CMD 沒有預設值

初步的感覺有點像
今天 Dockerfile 只有

FROM ubuntu

⚡ docker build -t ajdfajdfl/test-entrypoint .
⚡ docker run --rm --name test ajdfajdfl/test-entrypoint ls

也就是
預設會是這樣 ENTRYPOINT + CMD： /bin/sh -c "ls"