Adding support for a new node in WalT


WalT is currently provided with support for several kinds of nodes:

  • Raspberry Pi boards: models B, B+, 2B, 3B, 3B+ and 4B

  • Google Coral dev boards

  • Standard PC machines (x86 32bit or 64bit CPU)

  • Virtual nodes

Check-out walt help show node-install for more info.

But WalT can also support any other kind of hardware, without having to update its internal source code. This page explains how this can be done.


First, you should open an issue at in order to let us assist you in this process.

On the technical side, support for a new kind of node in WalT requires:

  • A network bootloader with appropriate configuration

  • A default walt image that will be assigned to newly detected nodes of this kind

In the meantime, or if this process proves impossible to achieve (e.g., there is no way to flash a network bootloader on this device), the WalT platform can still provide a limited set of useful features to interact with unmanaged devices (cf. walt help show unmanaged-devices).

Network bootloader

First, you may clone git repository This repository currently allows to generate SD card content of walt raspberry pi nodes, and USB device image of walt PC nodes. It can be a good starting point. Feel free to issue a pull request if you want your work on this repository to be included.

Currently, Raspberry pi nodes use U-Boot network bootloader. And PC nodes use iPXE network bootloader.

U-boot supports many single board computers, so you can probably use it for the new board. However, check that u-Boot can handle the embedded network adapter, it may not be the case. Support for newest boards may be limited at first, but usually improves over time.

In order to work properly, the bootloader should be configured to do the following on boot:

  1. If handling several sub-models (such as the bootloader configuration we provide for raspberry pi boards), identify the sub-model of the board currently booting (e.g. rpi-2-b).

  2. Perform a DHCP request. Important: the vendor class identifier (VCI) of the DHCP request must be set to walt.node.<type> (e.g. walt.node.rpi-2-b). This allows walt server to associate the default walt image appropriate for this type, on fist boot. Note that it is possible to set the UCI (User class identifier) to this value, instead of the VCI, if setting the VCI is not possible on this specific bootloader.

  3. Download script file start.uboot using TFTP. On server side, this request will be redirected to file [image]:/boot/<node-type>/start.uboot.

  4. Execute this script.

The script rpi/builder_files/boot.scr.txt in walt-node-boot repository is an example of a u-boot script which follows these steps.

Default walt image

In order to create a default walt image appropriate for this board, you should check out walt help show image-from-scratch.

As an example, the default images we provide are generated by the repository at:

In order to let walt use your image as the default for this node type, you must import it in walt own repository and rename it to waltplatform/<node-type>-default:latest. For this, run the following as root on the server:

$ podman pull docker-daemon:<docker-image>:<tag>
$ podman tag<docker-image>:<tag><node-type>-default:latest

Then you should let walt server daemon rescan its repository. Flag --refresh of command walt image show will cause this rescan:

$ walt image show --refresh

You can now try to boot the new node for the first time.

After this initial try, you can of course clone this default image to get your own copy, update it using walt image shell for instance, and use walt node boot to test your modifications. This will make debugging easier than having to refresh the default image again.

As an alternative, you can also use docker rather than walt to make modifications, and then force walt to clone the updated default image from the docker repository by using walt advanced update-default-images.

At the end of the debugging, in order to have your new default walt image pushed to the docker hub, you should notify us about it (add a comment to the issue you initially reported), and we will do it for you (since push authorization on waltplatform account is restricted).