How to reset kali linux password in windows subsystem for linux

I have installed Kali Linux subsystem on windows. And now I have forgotten the root password in Kali, there is just the terminal of Kali Linux and nothing else. How can I reset my password safely?

Note: I have installed both Ubuntu and Kali Linux installed at the same time But when I run bash by default it opens up ubuntu

Answer

I have installed both Ubuntu and Kali Linux installed at the same time But when I run bash by default it opens up Ubuntu.

In new Windows versions, users can install and run multiple GNU/Linux distributions. One can configure the default distribution (i.e. the distribution that comes up with wsl.exe) with wslconfig /s command. e.g. To open Kali with wsl.exe at first run, use this command wslconfig /s kali-linux or run kali.exe.

I have forgotten the root password in Kali, there is just the terminal of Kali Linux and nothing else. How can I reset my password safely?

First of all, I don't know if this procedure is safe or not. At the time of writing, WSL manages the default login user from DefaultUID registry (this may change in future). Close any opened WSL instance. To edit this registry value, open Registry Editor or regedit.exe from start menu or run dialog box. Go to this registry path or type this path with Ctrl + L in that Window:

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Lxss 

You may see one or multiple subkeys (like subfolders) with names something like {12345678-1234-1234-1234-123456789012} (called GUID). Double click on them to open one-by-one and match the DistributionName value with your desired distribution name, here it will be kali-linux (see below). Double click on the DefaultUID value and change it to ZERO. Zero is for root user and 1000 or 0x3e8 (in hexadecimal) for normal users.

Open wsl.exe in command prompt. The prompt changes from $ to # (means root user). Run passwd command in Kali, change root password as usual. Now go back to previous registry key, change Zero to previous value (or 3e8 in hex). Here is an example of the registry values:

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Lxss]
"DefaultDistribution"="{f029d4cd-b7ee-42bc-ae02-af8f2c97f495}"

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Lxss\{f029d4cd-b7ee-42bc-ae02-af8f2c97f495}]
"State"=dword:00000001
"DistributionName"="kali-linux"
"Version"=dword:00000001
"BasePath"="C:\\MyFiles\\kali-linux"
"KernelCommandLine"="BOOT_IMAGE=/kernel init=/init ro"
"DefaultUid"=dword:000003e8
"Flags"=dword:00000007

Further details: