How do I find out which random port Docker has chosen?

Question

I ran this:

$ docker run -p 8080 --rm my_container 

which I guess maps the container port 8080 to some random available port on the host. But how do I find out which port?

Answer 1

You can use the docker port command:

docker port my_container

This command output like the following (example with MySQL image):

3306/tcp -> 0.0.0.0:3306

The value before -> specifies the port on the container side. The value after -> specifies the chosen port on the host machine.

---

You can also run the container with a specific port on the host machine (if available):

docker run -p "80:8080" --rm my_container

This would give the following output on docker port:

8080/tcp -> 0.0.0.0:80