Containerd

Runc is a low-level implementation of a container runtime; containerd builds on top of it, and adds higher-level features, such as image transfer and storage, container execution, and supervision, as well as network and storage attachments. With this, it manages the complete life cycle of containers. Containerd is the reference implementation of the OCI specifications and is by far the most popular and widely-used container runtime.

Containerd has been donated to and accepted by the CNCF in 2017. There exist alternative implementations of the OCI specification. Some of them are rkt by CoreOS, CRI-O by RedHat, and LXD by Linux Containers. However, containerd at this time is by far the most popular container runtime and is the default runtime of Kubernetes 1.8 or later and the Docker platform.