Using WSL with cloud-init

In this guide, we will customize a Windows Subsystem for Linux (WSL) instance using cloud-init on Ubuntu.

Prerequisites

This guide assumes you are running within a Windows 11 or Windows Server 2022 environment. If wsl is already installed, you must be running version 2. You can check your version of wsl by running the following command in your terminal:

PS> wsl --version

Example output:

WSL version: 2.1.5.0
Kernel version: 5.15.146.1
WSLg version: 1.0.60
MSRDC version: 1.2.5105
Direct3D version: 1.611.1-81528511
DXCore version: 10.0.25131.1002-220531-1700.rs-onecore-base2-hyp
Windows version: 10.0.20348.2402

If you follow this guide while using a virtualized environment (including in the cloud), ensure that nested virtualization is enabled.

Install WSL

Note

If you have already installed WSL, you can skip this section.

PS> wsl --install

Example output:

Installing: Virtual Machine Platform
Virtual Machine Platform has been installed.
Installing: Windows Subsystem for Linux
Windows Subsystem for Linux has been installed.
Installing: Ubuntu
Ubuntu has been installed.
The requested operation is successful. Changes will not be effective until the system is rebooted.

Reboot the system when prompted.

Create some user data

User data is the primary way for a user to customize a cloud-init instance. Open Notepad and paste the following:

#cloud-config
write_files:
- content: |
    Hello from cloud-init
  path: /var/tmp/hello-world.txt
  permissions: '0777'

Save the file to %USERPROFILE%\.cloud-init\Ubuntu-24.04.user-data.

For example, if your username is me, the path would be C:\Users\me\.cloud-init\Ubuntu-24.04.user-data. Ensure that the file is saved with the .user-data extension and not as a .txt file.

Note

We are creating user data that is tied to the instance we just created, but by changing the filename, we can create user data that applies to multiple (or all) WSL instances. See WSL Datasource reference page for more information.

What is user data?

Before moving forward, let’s inspect our user-data file.

We created the following contents:

#cloud-config
write_files:
- content: |
    Hello from cloud-init
  path: /var/tmp/hello-world.txt
  permissions: '0770'

The first line starts with #cloud-config, which tells cloud-init what type of user data is in the config. Cloud-config is a YAML-based configuration type that tells cloud-init how to configure the instance being created. Multiple different format types are supported by cloud-init. For more information, see the documentation describing different formats.

The remaining lines, as per the Write Files module docs, creates a file /var/tmp/hello-world.txt with the content Hello from cloud-init and permissions allowing anybody on the system to read or write the file.

Obtain the Ubuntu WSL image

Ubuntu 24.04 is the first Ubuntu version to support cloud-init in WSL, so that is the image that we’ll use.

We have two options to obtain the Ubuntu 24.04 WSL image: the Microsoft Store and the Ubuntu image server.

Option #1: The Microsoft Store

If you have access to the Microsoft Store, you can download the Ubuntu 24.04 WSL image from within the app.

Click on the “Install” button to download the image. Then click “Open” to install the image.

Alternatively, you can use the following command to download and install the image:

PS> wsl --install --distribution Ubuntu-24.04

Option #2: The Ubuntu image server

If the Microsoft Store is not an option, we can instead download the Ubuntu 24.04 WSL image from the Ubuntu image server.

Create a directory under the user’s home directory to store the WSL image and install data.

PS> mkdir ~\wsl-images

Download the Ubuntu 24.04 WSL image.

PS> Invoke-WebRequest -Uri https://cloud-images.ubuntu.com/wsl/noble/current/ubuntu-noble-wsl-amd64-wsl.rootfs.tar.gz -OutFile wsl-images\ubuntu-noble-wsl-amd64-wsl.rootfs.tar.gz

Import the image into WSL, storing it in the wsl-images directory.

PS> wsl --import Ubuntu-24.04 wsl-images .\wsl-images\ubuntu-noble-wsl-amd64-wsl.rootfs.tar.gz

Example output:

Import in progress, this may take a few minutes.
The operation completed successfully.

Start the Ubuntu WSL instance

PS> wsl --distribution Ubuntu-24.04

Set up the Ubuntu WSL instance

The Ubuntu WSL instance will start, and you may be prompted for a username and password.

Installing, this may take a few minutes...
Please create a default UNIX user account. The username does not need to match your Windows username.
For more information visit: https://aka.ms/wslusers
Enter new UNIX username:
New password:
Retype new password:

Once the credentials have been entered, you should see a welcome screen similar to the following:

Welcome to Ubuntu Noble Numbat (GNU/Linux 5.15.146.1-microsoft-standard-WSL2 x86_64)

* Documentation:  https://help.ubuntu.com
* Management:     https://landscape.canonical.com
* Support:        https://ubuntu.com/pro

System information as of Mon Apr 22 21:06:49 UTC 2024

System load:  0.08                Processes:             51
Usage of /:   0.1% of 1006.85GB   Users logged in:       0
Memory usage: 4%                  IPv4 address for eth0: 172.29.240.255
Swap usage:   0%


This message is shown once a day. To disable it please create the
/root/.hushlogin file.
root@machine:/mnt/c/Users/me#

This indicates you are now in a shell inside the WSL instance.

Verify that cloud-init ran successfully

Before validating the user data, let’s wait for cloud-init to complete successfully:

$ cloud-init status --wait

Which provides the following output:

status: done

Now we can now see that cloud-init has detected that we running in WSL:

$ cloud-id

Which provides the following output:

wsl

Verify our user data

Now we know that cloud-init has been successfully run, we can verify that it received the expected user data we provided earlier:

$ cloud-init query userdata

Which should print the following to the terminal window:

#cloud-config
write_files:
- content: |
    Hello from cloud-init
path: /var/tmp/hello-world.txt
permissions: '0770'

We can also assert the user data we provided is a valid cloud-config:

$ cloud-init schema --system --annotate

Which should print the following:

Valid schema user-data

Finally, let us verify that our user data was applied successfully:

$ cat /var/tmp/hello-world.txt

Which should then print:

Hello from cloud-init

We can see that cloud-init has received and consumed our user data successfully!

What’s next?

In this guide, we used the Write Files module to write a file to our WSL instance. The full list of modules available can be found in our modules documentation. Each module contains examples of how to use it.

You can also head over to the examples page for examples of more common use cases.

Cloud-init’s WSL reference documentation can be found on the WSL Datasource reference page.