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I have Windows Subsystem for Linux, but I don't know which version I have, and many things won't work in version 1. How do I check my version?

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    @Rinzwind You are welcome to join with me requesting such at github.com/microsoft/WSL/issues/4555
    – K7AAY
    Sep 30, 2019 at 18:07
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    From that thread, it looks like the following bash command works: uname -r | grep Microsoft > /dev/null && echo "WSL1". -- It's a pretty adhoc way to detect it, but it will print "WSL1" if that's what you're running. Aug 12, 2020 at 23:23
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    @BrainSlugs83 Extremely fragile but works for me! In WSL1, uname -r ends with -Microsoft, in WSL2, it ends -microsoft-standard ... lower case "m"! Aug 14, 2020 at 9:09
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    @Rinzwind Any questions regarding WSL, including how to install it, are on-topic, in my opinion.
    – Flimm
    Aug 24, 2020 at 9:15
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    @Rinzwind If the question is on-topic, then so are the answers to that question. If someone asks how to create a bootable Ubuntu USB stick on Windows, then that question is on-topic, and so are all the answers to it, even if the answers mention unetbootin.exe . Same thing with WSL.
    – Flimm
    Aug 25, 2020 at 13:36

5 Answers 5

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  1. At a Windows 10 command prompt, run ver. Is the next-to-last numeric group version 18917 or higher? If so, it is possible you have WSL 2 but not yet verified. Go on to step A or B.
    If you do not see Windows version 18917 or higher, you have version 1.
    This illustrates the result when the OS is Build 16299:

    Version 16299

    A. Open Windows PowerShell or cmd and enter the command wsl -l -v. If version 2 is installed properly, you will see the version number. If you don't see a version number, or if you see an error message (Thank you, Cornea Valentin) you have version 1 (you may also see a version number '1' which could indicate that you're running v1 - see here). Uninstall it then reinstall it as per https://scotch.io/bar-talk/trying-the-new-wsl-2-its-fast-windows-subsystem-for-linux

    B. From the WSL shell prompt, run uname or uname -r. If the kernel version >= 4.19, it's WSL Version 2.

Why is this relevant?

WSL 1 was based on Microsoft's Linux-compatible kernel interface, a compatibility translation layer with no Linux kernel code.

WSL 2 was redesigned with a Linux kernel running in a lightweight VM environment, and innovators have found many more things they can do with WSL 2.

Windows 10 Version 2004 (build 19041.153 & later) enhances WSL2 further; see https://devblogs.microsoft.com/commandline/wsl2-will-be-generally-available-in-windows-10-version-2004/ and https://winaero.com/blog/wsl2-will-ship-with-windows-10-version-2004-with-kernel-updates-via-windows-update/ .

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    also if he get any errors after: wsl -l -v it's 100% wsl 1. Oct 5, 2019 at 15:04
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    I needed to use uname -r to see the kernel version, but the kernel version ended up being 4.4.0, which I'm pretty sure means WSL 1.
    – Keara
    Jun 12, 2020 at 15:27
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    Use uname -a to print kernel version. Jul 23, 2020 at 11:35
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    For me, wsl -l -v prints the usage info (i.e. doesn't work), but wsl -l --verbose prints the verbose list as intended. systeminfo.exe gives me OS Version: 10.0.19041 N/A Build 19041.
    – drkvogel
    Aug 10, 2020 at 14:35
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    I'm seeing 4.4, is that greater or less than 4.19?
    – quant
    Sep 17, 2020 at 22:48
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  1. Open PowerShell
  2. Check the version with wsl -l -v
  3. If at version 1, then update the version with wsl --set-version Ubuntu-20.04 2

Note: Changing the version of a running OS will terminate it. The name of the OS need not be Ubuntu-20.04 for you. Please select the actual name listed in wsl -l -v

If you are not able to update to version 2, then you may not be on the WSL 2 Kernel. This can be downloaded from Microsoft.

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  • Note on point 3, running it will instantly kill currently running instances of the OS selected, eg all instances of Ubuntu-20.02 in this case.
    – zshift
    Aug 22, 2020 at 21:40
  • Thanks for pointing that out, I added a note to point that out.
    – Jack
    Aug 23, 2020 at 7:44
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    @Jack, Having only one version of ubuntu, 18.04, I noticed that "wsl --set-version Ubuntu 2" worked for me without specifying the version. I suspect that's always the case.
    – Angelo
    Aug 28, 2020 at 1:05
  • This is the correct answer for me on Windows 10. Mar 29, 2021 at 1:23
  • Simply run wsl --status as shown here: youtube.com/watch?v=bRW5r7TK6KM Jan 22 at 23:40
2

In the WSL version I was running, I just typed uname -r to which I got the result

5.4.72-microsoft-standard-WSL2

So, I can say that its WSL2, so you can try running uname -r and check.

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    That will work as long as you are running the stock kernel, but it could be named differently if you use a custom kernel. Also, for reference, WSL1 kernels are something like "4.4.0-22000-Microsoft" (without the "-standard-WSL2"). I seem to recall that 4.x releases on WSL2 were just "-microsoft-standard" (without the "-WSL2), but I could be wrong. Nov 27, 2021 at 18:27
  • Ah I didn't know that, thanks for letting me know!
    – Luce
    Dec 8, 2021 at 10:52
1

Programmatically:

# Multiline 
wsl.exe -l -v |
iconv -f utf16 |
egrep "\b${WSL_DISTRO_NAME}\s+Running" |
tr -d '\r' |
sed 's/.*\([[:digit:]]\)[[:space:]]*/\1/'

Will return 1 or 2.

Line-by-line, this:

  • Executes wsl.exe -l -v to return the full list of all distributions you might have installed

  • Runs it through iconv to fix its malformed UTF16 output. You don't normally see the problem unless you try to grep it (or pipe it to something like hexdump -C), but you have to clean it up before you can grep it.

  • Matches the current instance (via $WSL_DISTRO_NAME) line

  • Removes the DOS line ending

  • Finds the version number in the line and outputs it

Thanks to this Super User answer for the concept.

This will work as long as Interop is enabled for WSL.

If Interop isn't enabled, then a fallback method is to check /proc/cmdline:

  • /proc/cmdline on WSL1 is BOOT_IMAGE=/kernel init=/init
  • /proc/cmdline on WSL2 is initrd=\initrd.img panic=-1 pty.legacy_count=0 nr_cpus=16

So:

  • grep -q "^BOOT_IMAGE" /proc/cmdline returns success on WSL1 but error on WSL2
  • grep -q "^initrd" /proc/cmdline returns success on WSL2 but error on WSL1

This currently works (and has for the last year, at least), but could change in the future if either the WSL1 or WSL2 architecture changes in some way. However, I expect that the /proc/cmdline is likely always going to differ between WSL1 and WSL2 and can be programmatically parsed to determine the current version.

-1

If you happen to be running Docker for Windows and you have WSL 1, then if you enter docker in the terminal for your WSL, you'll see the message The command 'docker' could not be found in this WSL 1 distro., which is a very clear confirmation.

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