How to Add or Modify Docker Container Port Mappings After Creation

If a container hasn't been built yet, you can add port mappings during creation by using multiple -p options in the docker run command, for 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

To modify or add ports on an already running container, first stop it: docker stop <container_id_or_name> Find the full container hash with:

docker inspect <container_id_or_name> | grep Id

Open the container's hostconfig.json (path: /var/lib/docker/containers/<hash>/hostconfig.json) using vim or vi. If you prefer, cd into the container directory first: cd /var/lib/docker/containers/<hash>* In hostconfig.json, locate the "PortBindings":{} object and add the desired mappings, e.g.:

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

Also update "ExposedPorts" in config.v2.json or config.json if those files contain port entries:

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

After editing, restart Docker and verify the changes:

# Restart Docker
service docker restart
# or
systemctl restart docker

# Inspect the container to confirm
docker inspect <container_id_or_name>

Finally, start the container again:

docker start <container_id_or_name>

Docker Desktop for Mac

On macOS, containers run inside a VM, so you need to enter that VM to edit the files. Use the tiny justincormack/nsenter1 image:

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

--rm

removes the helper container on exit. --privileged grants access to host devices. --pid=host shares the host's PID namespace, allowing you to see host processes.

Once inside the VM, navigate to /var/lib/docker/containers and edit hostconfig.json and, if needed, config.v2.json using vi (the image lacks vim).

vi /var/lib/docker/containers/<hash>/hostconfig.json
vi /var/lib/docker/containers/<hash>/config.v2.json

After modifications, restart Docker on macOS and verify the container configuration as described above.