Windows Subsystem for Linux

The wsl.exe command is used to manage distributions in the Windows Subsystem for Linux on the command-line. It can list available distributions, set a default distribution, and uninstall distributions.[31] The command can also be used to run Linux binaries from the Windows Command Prompt or Windows PowerShell.[32] wsl.exe replaces lxrun.exe which is deprecated as of Windows 10 1803 and later.[33]

WSLg is short for Windows Subsystem for Linux GUI built with the purpose of enabling support for running Linux GUI applications (X11 and Wayland) on Windows in a fully integrated desktop experience.[34] WSLg was officially released at the Microsoft Build 2021 conference. It is included in Windows 10 Insider build 21364 or later.[19] However, with the introduction of Windows 11 WSLg is finally shipping with a production build of Windows bringing support for both graphics and audio in WSL apps.[35] FreeRDP is used to encode all communications going from the RDP Server (in Weston) to the RDP Client (mstsc on Windows) according to the RDP protocol specifications. [36]

Prerequisites for running WSLg include:

• Windows 11 or Windows 10 Insider Preview builds 21362-21390.[34][37]
• A system with virtual GPU (vGPU) enabled for WSL is recommended, as it will allow you to benefit from hardware accelerated OpenGL rendering[34]

Firefox for Linux running on WSL

LXSS Manager Service is the service in charge of interacting with the subsystem (through the drivers lxss.sys and lxcore.sys), and the way that Bash.exe (not to be confused with the Shells provided by the Linux distributions) launches the Linux processes, as well as handling the Linux system calls and the binary locks during their execution.[38] All Linux processes invoked by a particular user go into a "Linux Instance" (usually, the first invoked process is init). Once all the applications are closed, the instance is closed.

WSL 1's design featured no hardware emulation / virtualization (unlike other projects such as coLinux) and makes direct use of the host file system (through VolFS and DrvFS)[39] and some parts of the hardware, such as the network, which guarantees interoperability. Web servers for example, can be accessed through the same interfaces and IP addresses configured on the host, and shares the same restrictions on the use of ports that require administrative permissions, or ports already occupied by other applications.[40] There are certain locations (such as system folders) and configurations whose access/modification is restricted, even when running as root, with sudo from the shell. An instance with elevated privileges must be launched in order to get "sudo" to give real root privileges, and allow such access.[21]

WSL 1 is not capable of running all Linux software, such as 32-bit binaries,[41][42] or those that require specific Linux kernel services not implemented in WSL. Due to a lack of any "real" Linux kernel in WSL 1, kernel modules, such as device drivers, cannot be run. WSL 2, however, makes use of live virtualized Linux kernel instances. It is possible to run some graphical (GUI) applications (such as Mozilla Firefox) by installing an X11 server within the Windows (host) environment (such as VcXsrv or Xming),[43] although not without caveats, such as the lack of audio support (though this can be remedied by installing PulseAudio in Windows in a similar manner to X11) or hardware acceleration (resulting in poor graphics performance). Support for OpenCL and CUDA is also not being implemented currently, although planned for future releases.[44][45] Microsoft stated WSL was designed for the development of applications, and not for desktop computers or production servers, recommending the use of virtual machines (Hyper-V), Kubernetes, and Azure for those purposes.[21]

In benchmarks WSL 1's performance is often near native Linux Ubuntu, Debian, Intel Clear Linux or other Linux distributions. I/O is in some tests a bottleneck for WSL.[46][47][48] The redesigned WSL 2 backend is claimed by Microsoft to offer twenty-fold increases in speed on certain operations compared to that of WSL 1.[5] In June 2020, a benchmark with 173 tests with an AMD Threadripper 3970x shows good performance with WSL 2 (20H2) with 87% of the performance of native Ubuntu 20.04.0 LTS. This is an improvement over WSL 1, which has only 70% of the performance of native Ubuntu in this comparison. WSL 2 improves I/O performance, providing a near-native level.[49] A comparison of 69 tests with Intel i9 10900K in May 2020 shows nearly the same relative performance.[50] In December 2020, a benchmark with 43 tests with an AMD Ryzen 5900X shows good performance with WSL 2 (20H2) with 93% of the performance of native 20.04.1 LTS. This is an improvement over WSL 1, which has only 73% in this comparison.[51]

Synaptic package manager running on WSL

Version 2 introduces changes in the architecture. Microsoft has opted for virtualization through a highly optimized subset of Hyper-V features, in order to run the kernel and distributions (based upon the kernel), promising performance equivalent to WSL 1. For backward compatibility, developers don't need to change anything in their published distributions. WSL 2 settings can be tweaked by the WSL global configuration, contained in an INI file named .wslconfig in the User Profile folder.[52][53]

The distribution installation resides inside an ext4-formatted filesystem inside a virtual disk, and the host file system is transparently accessible through the 9P protocol,[54] similarly to other virtual machine technologies like QEMU.[55] For the users, Microsoft promised up to 20 times the read/write performance of WSL 1.[4] From Windows an IFS network redirector is provided for Linux guest file access using the UNC path prefix of \\wsl$.

WSL 2 requires Windows 11,[56] or Windows 10 version 1903 or higher, with Build 18362 or higher, for x64 systems, and Version 2004 or higher, with Build 19041 or higher, for ARM64 systems.[7]