How to get the IP address of the docker host from inside a docker container

Question

As the title says. I need to be able to retrieve the IP address the docker hosts and the portmaps from the host to the container, and doing that inside of the container.

Answer 1

/sbin/ip route|awk '/default/ { print $3 }' 

As @MichaelNeale noticed, there is no sense to use this method in Dockerfile (except when we need this IP during build time only), because this IP will be hardcoded during build time.

Answer 2

As of version 18.03, you can use host.docker.internal as the host's IP.

Works in Docker for Mac, Docker for Windows, and perhaps other platforms as well.

This is an update from the Mac-specific docker.for.mac.localhost, available since version 17.06, and docker.for.mac.host.internal, available since version 17.12, which may also still work on that platform.

Note, as in the Mac and Windows documentation, this is for development purposes only.

For example, I have environment variables set on my host:

MONGO_SERVER=host.docker.internal 

In my docker-compose.yml file, I have this:

version: '3'  services:   api:     build: ./api     volumes:       - ./api:/usr/src/app:ro     ports:       - "8000"     environment:       - MONGO_SERVER     command: /usr/local/bin/gunicorn -c /usr/src/app/gunicorn_config.py -w 1 -b :8000 wsgi