how can I make a docker container run a command that will restart another container

Question

I made a fastAPI docker container, and it's running fine, unless 1 command...
I need it to restart another docker container when some event happen.

I have a server[host], running docker, docker is running containerA (fastAPI) and containerB ...
How can I make containerA run a command that will make the host execute this command:

docker restart containerB

Note, the host OS is linux.

I tried to use python's subprocess.run() , but it didn't work of course , containerA doesn't have docker installed, so of course it has no docker commands.
I've read articles saying that mounting unix socket will work, I tried mounting '/var/run/docker.sock:/var/run/docker.sock' but it didn't work as well.

If you have an idea how to make it work, I'd be grateful.
Thanks.

Answer 1

Mounting /var/run/docker.sock inside the container is the usual approach for this, as long as you’re comfortable exposing your host’s Docker daemon to the container. For this to work, you also need to ensure the Docker client binary (docker) is available inside the container; in your case it isn’t, you need to add it to the image.

Answer 2

This would be a better design to mount bind a directory, then create a file on the mount between host and container, and from host look changes on this directory, then restart docker container.

To bind mount, as usual from host:

docker run ... -v /host/path:/container/path:rw

On host, check directory:

while true; do
    if test -e "$dir/test"; then
        docker restart containerX
        rm -f "$dir/test"
    fi
    sleep 1
done

From the container:

touch "$dir/test"

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Even if it's technically possible to share the docker's socket to run docker commands inside containers, docker's experts suggest to not do because of security reasons.

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Read about DooD and DinD, maybe podman is better for security if you insist to use that approach. podman don't have a root service running like docker.