After installing the nvidia-container-toolkit and using nvidia-ctk runtime configure to register the NVIDIA runtime with Docker, the Docker daemon must be restarted. This step is necessary for the Docker service to reload its configuration and become aware of the newly added NVIDIA runtime. Without a restart, Docker will continue to operate with its old configuration, and attempts to run GPU-enabled containers will fail as it will not know how to use the nvidia runtime to expose the GPUs to the container.

(Assuming options are: A. Reboot the system, B. Run docker pull nvidia/cuda, C. Restart the Docker service, D. Configure the NVIDIA driver)

A: A full system reboot is unnecessary and excessive; only the affected service (Docker) needs to be restarted to apply the configuration changes.

B: Pulling a container image is a subsequent user action. It is not a required step to complete the installation and configuration of the toolkit itself.

D: The NVIDIA driver should already be installed before the container toolkit. This command does not affect the driver configuration.

1. NVIDIA Docs. (2023). NVIDIA Container Toolkit Installation Guide. Section: "Setting up Docker". The official guide explicitly lists restarting the Docker service as the final step after configuration. "sudo systemctl restart docker".

2. GitHub. NVIDIA/nvidia-docker repository. README.md. The installation instructions consistently show that after configuring the Docker daemon file (/etc/docker/daemon.json), a restart of the service is required.