Container Runtime

Container runtime refers to the software that is responsible for running containers. Containers are a method of operating system virtualization that allow applications to run in an isolated environment with their own filesystem, resources, dependencies, and configuration.

The container runtime pulls container images, unpacks them, creates isolated environments called containers, and starts the application processes inside these containers. Popular container runtimes include Docker Engine, containerd, CRI-O, and rkt. For example, when running a Docker container, the Docker Engine acts as the container runtime by managing the lifecycle of the container. It will pull the image specified in the Dockerfile, create a writable container layer, allocate resources like CPU and memory based on configurations, and start the main process defined in the image all while keeping the container isolated from the host system. The runtime continues to monitor and manage the container while the application runs inside it.