Easily Add or Modify Docker Container Port Mappings on macOS

Container Not Started?

If your container hasn't been built yet and you want to add port mappings, include the -p option when creating the container; add one -p for each port you wish to map. Example:

docker run --name api_dfo_hyperf_ws \
-v /Users/pudongping/glory/codes/dfo/api_dfo_hyperf:/api_dfo_hyperf \
-p 9502:9502 \
-p 9503:9503 \
-p 9504:9504 \
-p 9505:9505 \
-it \
--entrypoint /bin/sh \
alex/alex_api_dfo:v1.0

Container Already Running?

To modify or add ports you must first stop the running container.

All commands below use container id cbe26510c276 ; replace it with your own container id.

docker stop {container_name_or_id}

Example: docker stop cbe26510c276 Find the full container hash: docker inspect {container_name_or_id} | grep Id Then edit the hostconfig.json file located at:

vim /var/lib/docker/containers/{hash_of_the_container}/hostconfig.json

Or change to the container directory first:

cd /var/lib/docker/containers/{hash_of_the_container}*

vim hostconfig.json

Modify hostconfig.json

In hostconfig.json locate the "PortBindings":{} entry and add the desired mappings. For example, map host ports 8502 and 8505 to container ports 8502 and 8505:

{
    "PortBindings": {
        "8502/tcp": [
            {
                "HostIp": "",
                "HostPort": "8502"
            }
        ],
        "8505/tcp": [
            {
                "HostIp": "",
                "HostPort": "8505"
            }
        ]
    }
}

Usually the host port should match the container port for easier management.

If config.v2.json or config.json also contain port definitions, edit the "ExposedPorts" section accordingly:

{
    "Config": {
        "ExposedPorts": {
            "8502/tcp": {},
            "8505/tcp": {}
        },
        "Entrypoint": ["/bin/sh"]
    }
}

Restart Docker and verify the changes:

# Restart Docker
service docker restart
# or
systemctl restart docker

docker inspect {container_name_or_id}

Finally start the container again:

docker start {container_name_or_id}

Docker Desktop for Mac

How to log into the VM of Docker Desktop for Mac

Docker Desktop runs containers inside a Linux VM. The VM path can be found in the Docker Desktop settings under “Disk image location”. The simplest way to enter the VM is to run the tiny justincormack/nsenter1 image:

docker run -it --rm --privileged --pid=host justincormack/nsenter1

--rm

removes the container on exit. --privileged grants access to host devices. --pid=host shares the host’s process namespace.

Then navigate to /var/lib/docker/containers and edit config.v2.json and hostconfig.json with vi (the image does not include vim).