If pollsters asked for the Linux word of the year for 2022, "immutable" would definitely make the short list. The term, referring to an immutable filesystem, shows up wherever the topic turns to distributions. The technology is by no means new, but has not seen much use thus far.

For several years, the major commercial Linux vendors such as Red Hat and SUSE have been preparing for a paradigm shift with their enterprise software, focusing on protection both against unwanted intruders and against operating errors or systemic defects. A remedy against imponderables like this is a read-only filesystem mounted at boot time. However, this type of system also changes the format and method of delivering software and the package manager's position as a central component of a distribution.

Immutable filesystems are no longer limited to enterprise distributions and are beginning to show up on the home desktop. One immutable filesystem that has received advance praise is Vanilla OS [1], an ambitious Linux distribution that cleverly combines existing solutions instead of reinventing the wheel. Although Vanilla OS has only been in development for a few months, the creators, headed by project founder Mirko Brombin [2], recently released the first stable version Vanilla OS 22.10 Kinetic.

Ubuntu Underpinnings

Vanilla OS is based on a lean Ubuntu 22.10, a pure Gnome 43 without the Ubuntu customizations as the desktop and a separate installer. The distribution follows the Ubuntu release cycle. While this seems unspectacular so far, Vanilla OS differs significantly from typical Ubuntu derivatives. The first visual impression is colorful and reminds you more of Fedora than Ubuntu in terms of the layout (Figure 1). Vanilla OS's strategy also tends more towards Fedora Silverblue, but with different ingredients. At first glance, however, the system's special features are not apparent.

Figure 1: You can't see the Ubuntu underpinnings in Vanilla OS. Instead, it is more reminiscent of Fedora, but there is far more going on under the hood than its unassuming appearance suggests.

Vanilla OS is designed to be mostly immutable. By default, only /home, /etc, /opt, and /var can be written to in a separate partition. The system maps them in a container. This means that you can easily access configuration files, settings, and other important data that the installed packages need. The same applies to the files you create.

Double Root

ABRoot, Vanilla OS's core component, manages two partitions, each 20G in size and identified as a and b (Figure 2). They each consist of an identical root filesystem partitioned with Btrfs, which hosts the core applications. The system sets the active partition to read-only, which is why Vanilla OS requires at least 50GB of free disk space.

Figure 2: Two root partitions and a home directory require at least 50GB of disk space.

If possible, you will want to give the system more space, because 50GB only leaves you with 8GB for /home. Because the installer does not currently let you create partitions manually, it's important to be careful here. At install time, the setup formats the entire assigned hard disk and deletes all the existing data. This is due to change in the next version, Vanilla OS 2.0 Orchid [3].

From Apt to Apx

Another Vanilla OS core component is Apx, an Apt-based package manager developed in-house. Apx installs software from the Ubuntu archives, but it also lets you use packages from other distributions such as Fedora or Arch Linux. To do this, Apx creates containers based on the Distrobox tool that isolate applications from the root filesystem [4].

Vanilla OS distinguishes between updates and upgrades, the latter being a jump from, say, the current Ubuntu 22.10 to the upcoming version 23.04. Updates take place weekly or monthly, depending on the settings, and (if so desired, automatically) introduce small improvements, bug fixes, and security updates in the background.

These updates control the Vanilla System Operator (VSO) component. If you select the SmartUpdate option, VSO determines the update time by checking if the device is currently relatively idle and, in the case of laptops, if the battery level will let the procedure complete. You can configure VSO in Vanilla Control Center | Updates or at the command line.