Windows Subsystem for Linux

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.[21]

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

Developer(s)	Microsoft
Initial release	August 2, 2016 (2016-08-02)
Operating system	Microsoft Windows
Type	Command
Website	docs.microsoft.com/en-us/windows/wsl/

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.[22] The command can also be used to run Linux binaries from the Windows Command Prompt or Windows PowerShell.[23] wsl.exe replaces lxrun.exe which is deprecated as of Windows 10 1803 and later.[24]

Run uname command in WSL using PowerShell.

PS C:\temp> wsl uname --all
Linux WikiMachine 4.4.0-18362-Microsoft #1-Microsoft Mon Mar 18 12:02:00 PST 2019 x86_64 x86_64 x86_64 GNU/Linux

Example using sudo command from Command Prompt.

C:\temp> wsl sudo apt-get update
[sudo] password for username:
Hit:1 https://archive.ubuntu.com/ubuntu xenial InRelease
Get:2 https://security.ubuntu.com/ubuntu xenial-security InRelease [94.5 kB]

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)[25] 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.[26]

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.[16]

WSL 1 is not capable of running all Linux software, such as 32-bit binaries,[27][28] 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, can't 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),[29] 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.[30][31]

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.[16]

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.[32][33][34] 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.[3]

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.[35][36]

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,[37] similarly to other virtual machine technologies like QEMU.[38] For the users, Microsoft promised up to 20 times the read/write performance of WSL 1.[39] From Windows an IFS network redirector is provided for Linux guest file access using the UNC path prefix of \\wsl$.

WSL 2 requires 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.[40]