Using Docker-in-Docker

Using Docker-in-Docker or DinD is useful for docker development or when you want to have different isolated environments for a complex application like CI for example. Though I needed to use this approach to run a WordPress Multi-tenant architecture and it worked nicely.

There are two ways to run a DinD:

• Run a Docker container inside another Docker container and it will have its own Docker daemon and spawned containers
• Run a Docker container and share the host Docker socket with the container so that it runs containers on the host directly

I needed to use the second approach. The idea is to share the host socket /var/run/docker.sock:/var/run/docker.sock with the Docker container.

So an example command will be like this

docker run -it -v /var/run/docker.sock:/var/run/docker.sock docker:26-cli docker run nginx

This will run a nginx container from a docker container all shared on the same docker host

Read more:

• Using Docker-in-Docker for your CI or testing environment? Think twice