Create new virtual ext4 disk and attach to available WSL2

[phongmis]

Does WSL2 allow create new ext4 virtual disk and attach to available WSL2 instance ?
If WSL2 allow, how can I do that.

[guissalustiano]

just came out of the oven this functionality
https://devblogs.microsoft.com/commandline/access-linux-filesystems-in-windows-and-wsl-2

[ad-on-is]

just came out of the oven this functionality
https://devblogs.microsoft.com/commandline/access-linux-filesystems-in-windows-and-wsl-2

This blog post explains only how to mount a physical disk, but not how to mount a *.vhdx file.

[onomatopellan]

Not easy, but possible. I've been using this for weeks without problems:

https://gist.github.com/onomatopellan/90024008a0d8c8a2ed6fa57e8b64df54

[therealkenc]

This blog post explains only how to mount a physical disk

Documentation requests and PRs can be sent here.

[benhillis]

Yes it does.

[benapetr]

This is a terrible answer, he wanted to know HOW and you failed to answer that

[onomatopellan]

Well, that was easy. Just tried the new --mount function on latest insider build and works flawlessly.

Double clicking the vhdx file shows some error but it still appears on the list of wmic diskdrive list brief.

Now what I miss is

• an easy way to create a new ext4 dynamic vhdx disk (wsl.exe --new-vhdx ./storage.vhdx 😜 )
• automount the vhdx (using .wslconfig / wsl.conf files?)

[phongmis]

Thank you

[benapetr]

how did you create that disk formatted with ext4? I am on Home Windows and there is no Hyper-V manager. When I create a blank vhdx using disk manager, I can't mount it:

wsl --mount D:\wsl2\debian2.vhdx --bare 
Failed to attach disk 'D:\wsl2\debian2.vhdx' to WSL2: The parameter is incorrect.
Error code: Wsl/Service/AttachDisk/MountDisk/E_INVALIDARG 

[onomatopellan]

The easiest way to create a dynamic vhdx formatted in ext4 is installing a distro. You can for example extract the contents of Alpine.zip from https://github.com/yuk7/AlpineWSL/releases and after running the executable it will create a vhdx file on that folder.

[benapetr]

The easiest way to create a dynamic vhdx formatted in ext4 is installing a distro. You can for example extract the contents of Alpine.zip from https://github.com/yuk7/AlpineWSL/releases and after running the executable it will create a vhdx file on that folder.

I already have a distro (debian) but I have many disks in my system and I want to create a vhdx on separate disk and mount it inside of that distro so that I can move some data to different disk which is very large and has free space.

Using the "local" mounts that access the underlying NTFS disks via windows is extremely slow and NTFS doesn't support many linux features that I want.

[onomatopellan]

I've been using this method (for Ubuntu but it should also work for Debian) succesfuly for years. Basically consists in copying the alpine.exe to an external drive like D:, run it and create the .vhdx file and then use that .vhdx from your Debian trough the /mnt/wsl/Alpine mount point.

[craigloewen-msft]

Hey folks, just went through this process and wanted to write it down incase others stumbled upon it.

How to create a dynamically expanding VHDX with WSL

Create your base VHD

You can do this multiple ways. I'd recommend going to Hyper-V Manager -> Create New -> Virtual Hard Disk, and then make an expandable one up to whatever size you like.

Mount it into WSL using wsl --mount --bare

So first mount the VHD into Windows using:
Write-Output "\\.\PhysicalDrive$((Mount-VHD -Path ./ext4.vhdx -PassThru | Get-Disk).Number)"
And then mount it into WSL using the output from the above command. For reference mine was:
wsl --mount \\.\PhysicalDrive3 --bare

Format the VHD into ext4

You can use the dmesg command to see what drive it was mounted as. Mine was mounted under sdc. So I use the command:
sudo mkfs -t ext4 -i 12000 /dev/sdc
To format it as ext4 and I've changed the ratio of inodes in it to allow more inodes than normal.

Mount it in WSL

You can then remount this disk by running
wsl --unmount; wsl --mount \\.\PhysicalDrive3
And then you should have access to the disk!

[edwpang]

Can I use disk management to create the vhd?

[ophers]

yes. see https://winaero.com/create-a-new-vhd-or-vhdx-file-in-windows-10/

[philipmgrant]

Unfortunately this doesn't work on stable Windows 10 (because the --mount option isn't available): it requires an insider build or Windows 11.

[ophers]

You can try installing WSL2 preview from the Store: https://www.microsoft.com/store/productId/9P9TQF7MRM4R
If you hit issues, you can go back simply by uninstalling the store app.
A major feature I like is exactly the ability to mount a disk as regular user (does not need elevation), so I can place the command in "startup".

[josesa-xx]

WSLg and wsl --mount and other features were backported to Windows 10, you can download it from KB5020030

More details on microsoft devblog

[anodynos]

When I use this method to mount an NTFS image onto WSL Linux, I get very low writing speeds of around ~20Mb/Sec for a large file (from Windows to \wsl.localhost\Ubuntu22.04\mnt\mydisk).

Whereas when I copy the same file inside the main .vhdx (i.e to my /home/user/) OR when I format the same .vhdx as ext4, I get x10 the speed of around 200mb/sec (on a fast SSD).

I can't believe just the filesystem (NTFS vs ext4), is making it so slow. NTFS inside Linux works pretty well in general...

[ophers]

It's a known issue that accessing from windows into a WSL2 mounted volume is slow.
Assuming you do not need to concurrently access that volume from Windows and WSL2, you could:

1. Shutdown WSL
2. Mount the NTFS vhdx onto your Windows
3. Copy files in/out
4. Dismount the volume from Windows
5. Start the WSL2 instance