An OS made of Containers
In RancherOS, the Docker daemon runs as PID 1, the first process the kernel starts when it boots. We call this instance of Docker “System Docker,” as it is responsible for initiating system services, such as udev, DHCP and the console. Each of these system services run as containers. System Docker takes the place of the init system, such as sysvinit or systemd, in other Linux distributions.