如果镜像有入口脚本，Docker 无法启动交互式 shell

Question

My custom-made image ends with

ENTRYPOINT [ "/bin/bash", "-c", "/home/tool/entry_script.sh" ]

This is absolutely needed because at runtime, the first thing the user must do is to update an already cloned github project, and users will often forget to do it.

But then, when i try to launch using

docker run -it --rm my_image /bin/bash

i can see that the ENTRYPOINT script is being executed, but then the container exit.

I expect to have /bin/bash being executed and the shell to remain in interactive mode, due to -it flags.

What am I doing wrong?

UPDATE: I add my entry script

#!/bin/bash

echo "UPDATING GIT REPO";

cd /home/tool/cloned_github_tools_root
git pull
git submodule init
git submodule update

echo "Entrypoint ended";

Actually I've not kind of errors at runtime

Answer 1

When you set and entry point in a docker container. It is the only thing it will run. It's the one and only process that matters (PID 1). Once your entry_point.sh script finishes running and returns and exit code, docker thinks the container has done what it needed to do and exits, since the only process inside it exits.

If you want to launch a shell inside the container, you can modify your entry point script like so:

#!/bin/bash

echo "UPDATING GIT REPO";

cd /home/tool/cloned_github_tools_root
git pull
git submodule init
git submodule update

echo "Entrypoint ended";

/bin/bash "$@"

This starts a shell after the repo update has been done. The container will now exit when the user quits the shell.

The -i and -t flags will make sure the session gives you an stdin/stdout and will allocate a psuedo-tty for you, but they will not automatically run bash for you. Some containers don't even have bash in them.

Answer 2

I think the original question and answer are pretty good (thank you!). However I had the same exact problem but the provided solution did not work for me. I ended up wasting a lot of time figuring out what I was doing wrong. Hence I came up with a solution that should work all the time, if this could save time for others. In my docker entry point I'm sourcing a shell script file from Intel compiler and the received parameters $@ are somewhat changed by the 'source' command. Then when ending the script with /bin/bash "$@" the original parameters are gone. Here is my updated version that would be safer for all use cases:

#!/bin/bash

# Save original parameters
allparams=("$@")

echo "UPDATING GIT REPO";

cd /home/tool/cloned_github_tools_root
git pull
git submodule init
git submodule update

echo "Entrypoint ended";

# Forward initial parameters
/bin/bash "${allparams[@]}"