Running GNOME in a Container

Adam Verslype — Wed, 07 Aug 2019 19:00:00 +0000

Containerizing the GUI separates your work and play.

Virtualization has always been a rich man's game, and more frugal enthusiasts—unable to afford fancy server-class components—often struggle to keep up. Linux provides free high-quality hypervisors, but when you start to throw real workloads at the host, its resources become saturated quickly. No amount of spare RAM shoved into an old Dell desktop is going to remedy this situation. If a properly decked-out host is out of your reach, you might want to consider containers instead.

Instead of virtualizing an entire computer, containers allow parts of the Linux kernel to be portioned into several pieces. This occurs without the overhead of emulating hardware or running several identical kernels. A full GUI environment, such as GNOME Shell can be launched inside a container, with a little gumption.

You can accomplish this through namespaces, a feature built in to the Linux kernel. An in-depth look at this feature is beyond the scope of this article, but a brief example sheds light on how these features can create containers. Each kind of namespace segments a different part of the kernel. The PID namespace, for example, prevents processes inside the namespace from seeing other processes running in the kernel. As a result, those processes believe that they are the only ones running on the computer. Each namespace does the same thing for other areas of the kernel as well. The mount namespace isolates the filesystem of the processes inside of it. The network namespace provides a unique network stack to processes running inside of them. The IPC, user, UTS and cgroup namespaces do the same for those areas of the kernel as well. When the seven namespaces are combined, the result is a container: an environment isolated enough to believe it is a freestanding Linux system.

Container frameworks will abstract the minutia of configuring namespaces away from the user, but each framework has a different emphasis. Docker is the most popular and is designed to run multiple copies of identical containers at scale. LXC/LXD is meant to create containers easily that mimic particular Linux distributions. In fact, earlier versions of LXC included a collection of scripts that created the filesystems of popular distributions. A third option is libvirt's lxc driver. Contrary to how it may sound, libvirt-lxc does not use LXC/LXD at all. Instead, the libvirt-lxc driver manipulates kernel namespaces directly. libvirt-lxc integrates into other tools within the libvirt suite as well, so the configuration of libvirt-lxc containers resembles those of virtual machines running in other libvirt drivers instead of a native LXC/LXD container. It is easy to learn as a result, even if the branding is confusing.

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