Lightweight host for Linux system containers.

vpsAdminOS is an operating system that serves as a host for container virtualization. It is based on not-os and NixOS.

vpsAdminOS was designed for purposes of vpsFree.cz, a non-profit association that provides virtual servers to its members. We were using OpenVZ Legacy since 2009, but needed to upgrade to a newer kernel, as modern Linux distributions stopped supporting the OpenVZ Legacy kernel. We didn't like the new OpenVZ 7 and seemed to have different needs than what LXC/LXD provided, so we decided to create our custom toolset to manage the containers to bring us closer to the experience of OpenVZ on upstream kernels. vpsAdminOS is built on:

vpsAdminOS provides means to create and manage system containers, which look and feel as much as a virtual machine as possible. It focuses on user namespace and cgroup management to isolate containers, all containers are running as unprivileged. One can set resource limits on a single container or groups of containers, allowing for fine-grained control and resource sharing.

osctl/osctld is an abstraction on top of LXC, managing system users, LXC homes, cgroups and system containers. vpsAdminOS uses ZFS to store containers and configuration. We have patched ZFS for seamless integration with user namespaces, i.e. user/group id mapping on the file system level, until a proper solution is provided in upstream to avoid chowning all containers' files into appropriate user namespaces.