LXCFS is a simple userspace filesystem designed to work around some current limitations of the Linux kernel.
Specifically, it's providing two main things
The code is pretty simple, written in C using libfuse.
The main driver for this work was the need to run systemd based containers as a regular unprivileged user
while still allowing systemd inside the container to interact with cgroups.
Now with the introduction of the cgroup namespace in the Linux kernel, that part is no longer necessary
on recent kernels and focus is now on making containers feel more like a real independent system through
the proc masking feature.
LXCFS is free software and is developed under the Apache 2 license.