LXD is a modern, secure system container and virtual machine manager developed by Canonical. It provides a REST API over a Unix socket and HTTPS, a command-line client (lxc), and an in-guest agent (lxd-agent). The architecture is a monolithic daemon with pluggable storage drivers (ZFS, Btrfs, LVM, Ceph, dir, and enterprise SAN), network drivers (bridge, OVN, macvlan, SR-IOV, physical), and device passthrough (GPU, USB, NIC, TPM, proxy). It supports clustering via dqlite/Raft for high availability, fine-grained authorization via OpenFGA, OIDC authentication, and ACME certificate provisioning. The codebase is written in Go with CGo for low-level Linux operations (namespaces, seccomp, AppArmor, cgroups) and includes extensive unit and integration tests. Key features include live migration, incremental backups, cloud-init integration, and a built-in metrics endpoint for Prometheus.
The Moby project is the upstream open-source project for Docker Engine, implementing a container platform with daemon/client architecture. It provides container lifecycle management, image handling, networking, storage, and orchestration capabilities through a highly modular design with swappable components for storage drivers, network drivers, logging drivers, and authorization plugins. The codebase demonstrates strong engineering practices including context propagation, consistent error handling, plugin architecture, and functional options patterns. The system uses containerd as the underlying container runtime and exposes both HTTP and gRPC APIs for client interaction.