linuxcontainers.org is the umbrella project behind LXC, LXD and LXCFS.
The goal is to offer a distro and vendor neutral environment for the development of Linux container technologies.
Our main focus is system containers. That is, containers which offer an environment as close as possible as the one you'd get from a VM but without the overhead that comes with running a separate kernel and simulating all the hardware.
LXC is the well known set of tools, templates, library and language bindings. It's pretty low level, very flexible and covers just about every containment feature supported by the upstream kernel.
LXC is production ready with LXC 1.0 getting 5 years of security updates and bugfixes (until April 2019).
LXD is the new LXC experience. It offers a completely fresh and intuitive user experience with a single command line tool to manage your containers. Containers can be managed over the network in a transparent way through a REST API. It also works with large scale deployments by integrating with OpenStack.
Userspace (FUSE) filesystem offering two main things:
It's designed to workaround the shortcomings of procfs, sysfs and cgroupfs by exporting files which match what a system container user would expect.
CGManager is our cgroup manager daemon. It's designed to allow nested unprivileged containers to still be able to create and manage their cgroups through a DBus API.
CGManager was used by default with LXC in Ubuntu since April 2014 and then by other distributions as they started needing working unprivileged containers.
It has now been deprecated in favor of the CGroup namespace in recent Linux kernels. On older kernels, LXCFS still offers a cgroupfs emulation that can be used instead of cgmanager and is more widely compatible with existing userspace.