The LXD container-management system is no longer a part of the linuxcontainers.org project:
Canonical, the creator and main contributor of the LXD project has decided that after over 8 years as part of the Linux Containers community, the project would now be better served directly under Canonical’s own set of projects.
While the team behind Linux Containers regrets that decision and will be missing LXD as one of its projects, it does respect Canonical’s decision and is now in the process of moving the project over.