Microsoft's latest Windows 10 preview lets users attach and mount a physical disk inside their Windows Subsystem for Linux 2 (WSL 2) distribution of choice.
The new feature is available in Windows 10 Insider Preview build 20211, which Microsoft has just released to Windows Insiders in the Dev Channel.
The feature lets users access Linux file systems, such as ext4, that aren't natively supported by Windows. It also means those who are dual-booting Windows and Linux with different disks can now access Linux files from Windows.
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Additionally, after mounting a physical disk, Windows 10 WSL 2 users can get to the Linux files it contains using the Windows File Explorer app, building on the File Explorer WSL integration Microsoft introduced earlier this year, which included a new Linux penguin icon in File Explorer. Users need to navigate to \wsl$ in File Explorer and then go to the mount folder.
The key new WSL 2 feature that Microsoft is adding to support non-native Windows file systems is 'wsl --mount', which can be run from a PowerShell window with administrative privileges. This lets users mount a physical disk inside WSL 2, with the feature attempting to mount the disk by default as ext4. 'wsl --unmount' lets users unmount and detach the disk from WSL 2.
The new preview builds on Microsoft's efforts to improve Linux on the Windows 10 desktop in 2020.
Microsoft notes there are three main current limitations to the feature. Only whole disks can be attached to WSL 2, so users can't attach a partition.
"Concretely, this means that it's not possible to use wsl --mount to read a partition on the boot device, because that device can't be detached from Windows," explains Microsoft in WSL documentation.
It doesn't support USB flash drives at this time, but USB disks are supported.
Also, Microsoft notes that "only file systems that are natively supported in the kernel can be mounted by wsl --mount".
"This means that it's not possible to use installed file system drivers (such as NTFS-3G for example) by calling wsl --mount."
Microsoft has also confirmed it is investigating user reports that surfaced this week that the September 2020 Patch Tuesday update breaks WSL 2. The issue is listed among several known issues with this preview build.
"We are investigating an issue affecting Windows Subsystem for Linux 2 distros where users can receive the error: 'The remote procedure call failed' on startup," Microsoft noted.
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The preview 20211 contains several bug fixes too, including a bug that stopped certain 32-bit applications running on a 64-bit OS from being properly promoted to the discrete GPU for hybrid configurations.
Microsoft has also fixed a Start menu glitch causing tiles to display an 'Update in progress' bar after an app had been successfully updated. Some app icons were appearing smaller than they should be. It also includes fixes for Arm64 devices causing Start crashes for certain apps, hanging issues affecting the lock screen and ShellExperienceHost.exe.
The build fixes an issue that was causing Windows update to get stuck while downloading the update and users will no longer get asked to reinstall a .NET update after each flight.