How to set default user for manually installed WSL distro?

I have cloned a WSL distro using wsl --export and wsl --import, but now, running wsl newdistro always logs me in as root. I understand that the lxrun command is deprecated and want to avoid it. The docs recommend using distroname.exe config, but that doesn't work, since this one doesn't have a corresponding executable.

As of the time of this writing, there are at least three (let's call it 3.5) different methods of changing/setting the default user in an imported WSL instance. While the two that have already been mentioned still work, there is a Microsoft recommended way to do it that hasn't been mentioned yet in this question.

Method 1 - /etc/wsl.conf

The current Microsoft recommended way of setting the username in an instance is to create a /etc/wsl.conf in the instance with the following setting:

[user]
default=username

Changing, of course, username to be your default username.

Exit your distro/instance, then issue a wsl --terminate <distroname> from PowerShell or CMD. When you restart, the default user should be set.

This is safer and less error-prone than the registry-based methods.

Method 2 - Registry Key

Setting the registry key per @harrymc's answer.

Method 3 - LxRunOffline

Using LxRunOffline to set the registry entry, as described in @Jaime's answer. Ultimately this has the same effect as Method 2.

Semi-method 4 - Runtime user selection via wsl commandline argument

The username can be selected when starting any WSL instance by:

wsl -u username or wsl -d distroname -u username, etc.

For instance, wsl -d Ubuntu -u root.

Side Note: This question was specifically about setting the default username in an imported instance. However, for completeness, you can also set the default username for a distro that was installed from the Store (or wsl --install) with:

<distro>.exe config --default-user <username>

For instance, if you installed "Ubuntu 20.04" from the Store, you would use:

ubuntu2004.exe config --default-user <username>

The .exe here is an "App Execution Alias" in Windows. You can check the name by going to "Manage app execution aliases" in the Windows System Settings.

The normal command syntax is for example:

ubuntu config --default-user new_user_name

However, this does not work for an imported distro, which is started by the following command :

wsl --distribution <DistributionName>

Try this undocumented method:

• Use regedit and navigate to the key:
  HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Lxss
• Examine its subkeys for a distribution that has the right name in the item DistributionName
• Create or modify a DWORD item named DefaultUid and set it to the user-id (uid) of your default user. Here root user is id 0 while the first user id is 1000 (0x3e8).

If this does not work for your setup, you would need to run as:

wsl --distribution ubuntu -u user_name

For more information see :

• Export and Import WSL Linux Distro in Windows 10
• Set Default User for WSL in Windows 10.

If you are installing some custom distributions in WSL, you will not get a "distroname.exe" command to change the configuration. You may use LxRunOffline to change the default user. This toolset can be installed in Windows using choco install lxrunoffline.

Get the default user id of a distro

LxRunOffline allows you get and set the default user id (uid) for any installed distributions. For instance, if you have a distro named newdistro you may check the default user using gu (get default user) and -n with the name of the distribution:

lxrunoffline gu -n newdistro 

The command returns a number, the user id of the default user:

• the root user has the 0 user-id
• the default user created during the install has the 1000 user id.

Set the default user id for a distro

If you want to set the root as the default user, you can make it using su (set default user) with -n and the name of the distro, and -v with the user id, i.e., 0 for the root.

lxrunoffline su -n newdistro -v 0