How to debug network issues in Docker

In case of network-related issues in Docker, or to verify that a hostname can be resolved and hosts can reach each other, a strategy that is often used is to docker exec into one of the containers and execute diagnostic tools from within the container. Because of the way the REST API image is built, no operating system tools are available in the container, so this strategy is not available.

To enable network debugging, a special service called debughost is defined in the Docker Compose file. It can start an interactive container that has curl available and is connected to all defined networks. Being a Debian-based image, additional tools can be installed via APT, like iproute2 or iputils-ping.

To start the container, run: