Docker: Connect to host from container on Linux

If you’re coming from the Mac, you’re probably used to connecting to the host from inside a container with the address host.docker.internal. On Linux, however, this does not work out of the box.

Docker CLI

If you run the following command on a Linux machine, you will see that DNS resolution is not working:

docker run --rm alpine ping -c 1 host.docker.internal

To fix this, we need to set the DNS name manually:

docker run --add-host=host.docker.internal:host-gateway --rm alpine ping -c 1 host.docker.internal

Instead of host.docker.internal you could use any other name.

Docker Compose

To achieve the same result in Docker Compose, use the extra_hosts property.

Create a docker-compose.yml file:

version: '3.9'

services:
  test:
    image: alpine
    extra_hosts:
      - 'host.docker.internal:host-gateway'

Test it with:

docker-compose run --rm test ping -c 1 host.docker.internal

Further reading

• Overview of Docker container communication options
• Set specific ip address by creating a custom network

Tags

#devops #docker #dx #linux

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