Docker-in-Docker (DinD) refers to the act of running Docker containers within another Docker container. With Docker-in-Docker (DinD), you can build, run and manage Docker containers from inside a container as if it were a virtual machine.
Docker images capable of running Docker engine internally are available on the Docker Hub registry. These images are primarily used for testing environments.
Here are the simplified steps to get Docker-in-Docker running:
1. Get a Docker image capable of running Docker internally:
You can pull a DinD image from Docker Hub with this command:
```
docker pull docker
```
This Docker image has Docker pre-installed and can run the Docker client command line.
1. Run the DinD container
After pulling the Docker image, you can start running your Docker-in-Docker container with this command:
```
docker run —privileged —name dind -d docker:dind
```
The `—privileged` flag will allow the container to access the host’s Docker daemon. This is vital for initiating the Docker-in-Docker functionality.
The `—name dind` attribute sets the name of the container to `dind`.
The `-d` flag tells Docker to run the container in the background and print the container ID.
1. Interact with the DinD container
To interact with your newly created DinD container:
```
docker exec -it dind sh
```
The `docker exec -it dind sh` command opens a shell (sh) into the `dind` container. Once inside the shell, you can run any ordinary Docker command.
Please note running Docker inside a Docker container, or Docker-in-Docker (DinD) is primarily used for testing and is not usually recommended for production environments. Moreover, running Docker in Docker can have some complex security implications.
Additionally, there might be limitations depending on your host system. It’s critical to comprehend why you require DinD for your specific application and to understand other possible methods and third-party tools.
