A container init so simple it's effectively brain-dead.

containerd is a daemon with an API and a command line client, to manage
containers on one machine. It uses runC to run containers according to the OCI
specification. containerd has advanced features such as seccomp and user
namespace support as well as checkpoint and restore for cloning and live
migration of containers.

Docker runs unix processes with strong guarantees of isolation and repeatability across servers. Docker is a great building block for automating distributed systems: large-scale web deployments, database clusters, continuous deployment systems, private PaaS, service-oriented architectures, etc.

go-mtree is a reimplementation of the BSD utility mtree(8) for GNU/Linux,
focusing on UX compatibility. In addition, it exposes a library allowing for
other developers to implement effective filesystem verification and comparison.

LXC is the well-known and heavily tested low-level Linux container runtime.

LXCFS is a small FUSE filesystem written with the intention of making Linux containers feel more like a virtual machine. It started as a side-project of LXC but is useable by any runtime.

LXD is a next generation system container manager. It offers a user experience similar to virtual machines but using Linux containers instead.

runc is a CLI tool for spawning and running containers according to the OCI
specification. It is designed to be as minimal as possible, and is the workhorse
of Docker. It was originally designed to be a replacement for LXC within Docker,
and has grown to become a separate project entirely.

skopeo is a command line utility for various operations on container images and
image repositories. skopeo is able to inspect a repository on a Docker registry
and fetch images layers. skopeo can copy container images between various
storage mechanisms.

umoci modifies Open Container images.

umoci intends to be a complete manipulation tool for OCI images. In particular,
it should be seen as a more end-user-focused version of the oci-image-tools
provided by the OCI. The hope is that all of this tooling will eventually be
merged with the upstream repository, so that it is always kept up-to-date by
the Open Container Initiative community.