How WSL Actually Packages and Distributes Linux Distros

Installing a Linux distro through WSL feels app-store-simple — pick Ubuntu or Debian from the Microsoft Store, click install, done. Underneath that simplicity is a genuinely straightforward packaging model: a root filesystem tarball plus a small amount of registration metadata.

What a “WSL distro” actually is, technically

At its core, a WSL distro is a root filesystem tarball (a compressed archive containing an entire Linux filesystem tree, similar in concept to what a container image’s filesystem layer contains) plus a small launcher application and registration with the WSL platform’s distro list — considerably simpler than it might seem from the Microsoft Store installation experience.

Why this makes exporting and importing distros straightforward

wsl --export Ubuntu ubuntu-backup.tar
wsl --import UbuntuCopy C:\WSL\UbuntuCopy ubuntu-backup.tar

Because a distro instance is fundamentally just a filesystem tarball plus registration, exporting one is literally packaging up its current filesystem state, and importing is registering a new distro instance from that same tarball — no more complex than that, which is why backup, cloning, and migration between machines work as cleanly as they do.

Why this also makes custom, non-Store distros possible

Since any root filesystem tarball can be imported as a distro, you’re not limited to the specific distros Microsoft or distro maintainers publish through the Store — a custom-built filesystem tarball (for a specialized environment, a specific team’s standardized dev environment, or an unofficial distro entirely) can be imported and used identically to an official one.

What actually gets stored where

Each imported or Store-installed distro instance’s filesystem lives in its own .vhdx virtual disk file under your Windows user profile — meaning multiple installed distros are genuinely separate filesystem instances, not shared installations, and each has its own independent state, packages, and configuration.

Why registration metadata matters beyond just the filesystem

The WSL platform layer tracks each registered distro’s default user, default working directory, and various per-distro settings separately from the filesystem tarball itself — which is why wsl --export and --import alone don’t perfectly preserve every configuration detail (default user, in particular, sometimes needs resetting after import) even though the underlying filesystem transfers completely.

What “cloning” a distro really means in this model

wsl --export Ubuntu temp.tar
wsl --import UbuntuClone C:\WSL\UbuntuClone temp.tar

Because import creates a genuinely independent distro instance from the exported tarball, this is real cloning — the new instance shares no ongoing state with the original after the import completes, unlike, say, a symlink or reference-based approach that would keep the two instances connected.

Why this simple underlying model is a genuine strength

A more complex, opaque distro installation mechanism would make backup, cloning, and custom-distro creation all considerably harder — the fact that a WSL distro reduces to “a filesystem tarball plus some registration metadata” is exactly what makes backing up and restoring a distro a straightforward, well-understood operation rather than something requiring specialized backup tooling.

The tar.gz appx-adjacent packaging Microsoft actually publishes

Store-distributed distros specifically ship as an application package (built around the same underlying packaging technology Windows uses for Store apps generally) that bundles a compressed root filesystem tarball alongside the small launcher and registration components. Microsoft and distro maintainers (Canonical for Ubuntu, the Debian project, and others) publish and update these packages independently — meaning an update to, say, Ubuntu’s Store-distributed WSL package is a separate event from any update to the WSL platform layer itself, and separate again from an update to the underlying WSL2 kernel, each moving on its own release cadence.

Building a genuinely custom distro from any compatible root filesystem

Because the import mechanism accepts any correctly-structured root filesystem tarball, tools exist specifically to help build one from scratch or from an existing container image — a Docker image’s exported filesystem, for instance, can serve as the starting point for a custom WSL distro tarball, since a container image’s root filesystem and a WSL distro’s expected root filesystem share the same fundamental Linux filesystem-tree structure. This is precisely why “build a standardized team development environment and distribute it as an importable WSL distro” is a workable, real pattern for organizations wanting consistent tooling across every developer’s machine, without depending on the Microsoft Store’s own distro catalog covering their specific needs.

Version pinning as a direct consequence of this model

Because each distro instance is a genuinely separate filesystem, holding one distro back at a specific package version while running a newer version in a second, independently registered instance is straightforward — install a second distro from the same base image, keep it deliberately unpatched, and use it specifically for testing compatibility against an older environment. This is a natural consequence of the packaging model’s separation, not a special feature requiring dedicated tooling.

What doesn’t transfer automatically, and why checking after import matters

Beyond the default-user quirk already mentioned, a few other things live at the registration layer rather than inside the filesystem tarball itself: the distro’s display name as WSL shows it, and certain per-distro settings configured through the WSL platform rather than through /etc/wsl.conf inside the filesystem. After any import — whether from an official Store package or a custom-built tarball — checking these registration-level details explicitly, rather than assuming a successful wsl --import means every configuration detail carried over identically to the source, avoids a class of “why does the imported copy behave slightly differently” confusion.

Confirm a custom or imported distro’s actual package versions directly rather than assuming they match the source image, since the export/import cycle itself doesn’t perform any updates along the way.

Why the tarball model made third-party distro projects possible at all

Beyond individual custom images built for a single team, the same simple packaging model is what let entirely separate projects publish and maintain their own WSL-compatible distro images independent of Microsoft’s own Store catalog — a community or vendor only needs to produce a correctly-structured root filesystem tarball and a small registration manifest to make their own Linux environment installable through the exact same wsl --import mechanism everyone else uses, without needing any special cooperation from Microsoft or inclusion in the official Store listing to reach real users.

Related:

Sources: