Wslhost.exe

wslhost.exe is a Windows executable that's used to display desktop notifications, and run Linux processes in the background.

COM server

When running as COM server, wslhost.exe registers a NotificationActivatorFactory, which is then used to display desktop notifications to the user.

Notifications can be used to:

• Notify the user about a WSL update
• Warn the user about a configuration error
• Notify the user about a proxy change

See: src/windows/common/notifications.cpp

Background processes

When wsl.exe terminates before the associated Linux processes terminates, wslhost.exe takes over the lifetime of the Linux process.

This allows Linux processes to keep running Windows commands and access the terminal even after the associated wsl.exe terminates.

See src/windows/wslhost/main.cpp and interop