NSL (NSpawn Subsystem for Linux) offers WSL-like persistent Linux machines on Linux hosts

Introduction to NSL

NSL, or NSpawn Subsystem for Linux, introduces a mechanism for Linux hosts to run persistent Linux machines, drawing a parallel to how Windows Subsystem for Linux (WSL) functions on Windows. Each machine operates as a complete distribution with its own set of packages and services, contained within a systemd-nspawn container inside a small virtual machine.

Key Features and Functionality

Users can access any supported distribution with a single command, with `nsl` opening a login shell in the default machine and `nsl run` executing specific commands. The system integrates host files, making `$HOME`, `/run/media/USER`, and `/mnt` accessible within the machine at `/mnt/host`, while preserving user identity (username, UID, GID) and passwordless sudo. Network services listening within a machine are accessible on the host's `127.0.0.1` at the same port, and Wayland applications can display windows directly on the host desktop.

Distribution Support and Isolation

NSL supports seven signed distributions: Debian, Ubuntu, Fedora, CentOS Stream, Arch, openSUSE Tumbleweed, and Leap. These images are rebuilt weekly and verified through the Frostyard publishing workflow. For security, an `--isolated` option provides a machine with its own VM, preventing access to host files, desktop, or actions, suitable for untrusted software.

Host System Integrity

NSL operates as a user-level process, ensuring the host system remains clean. It does not install host packages, alter device permissions, modify groups, or change sudoers configurations. This design aims to maintain the host's atomic state.

Current Status and Compatibility

NSL is currently in a pre-release state, with v0.4.0 being the first release of its current design. Earlier versions (v0.3.0 and prior) are retired prototypes. The tested host environment includes Snow Linux 13 on x86-64 with systemd 261.2, QEMU 10.0.13, virtiofsd 1.13.2, and GNOME Wayland.