DinD(Docker Inside Docker)

Mount the Docker Socket and Devices

docker run -it --gpus all --runtime=nvidia \
  -v /var/run/docker.sock:/var/run/docker.sock \
  -v /usr/bin/docker:/usr/bin/docker \
  -v /dev/nvidia0:/dev/nvidia0 \
  -v /dev/nvidiactl:/dev/nvidiactl \
  -v /dev/nvidia-uvm:/dev/nvidia-uvm \
  --name outer-nv-container nvidia/cuda:12.2.0-base-ubuntu22.04

Security Issue

running Docker-in-Docker (DinD) with GPU support does indeed involve passing a higher permission level from the host system into the outer container. Specifically:

1. Privileged Mode

• When you run the outer container with the --privileged flag, you are granting it elevated permissions that allow it to manage devices, execute system-level commands, and access resources typically restricted for containers. This elevated permission is crucial for running Docker within Docker, as it allows the outer container to start and manage its own Docker daemon and containers.

2. Mounting the Docker Socket

• By mounting the Docker socket from the host (/var/run/docker.sock) into the outer container, you give the container direct access to the host’s Docker daemon. This enables the outer container to execute Docker commands as if it were running on the host itself. This also means the containers run inside the outer container are effectively managed by the host’s Docker daemon.

3. Device Access

• To use the GPU, you pass through GPU device files like /dev/nvidia0, /dev/nvidiactl, and other necessary Nvidia device files into the container. This allows the containerized Docker instance to directly interface with the GPU, utilizing the host’s Nvidia drivers and CUDA libraries.

4. Security Implications

• While passing these permissions allows for powerful configurations like DinD with GPU support, it also introduces significant security risks. For example, the outer container (and any containers it runs) can potentially modify or control the host system. This is why running in privileged mode and mounting system-level resources like the Docker socket should be done cautiously and only in trusted environments.

Conclusion

The permission level, including device access and privileged mode, is indeed passed into the DinD setup. This allows the inner Docker containers to function correctly, particularly when using specialized hardware like GPUs. However, with great power comes great responsibility—ensure that this configuration is secure and controlled.