meta-moonforge-rauc-update

Adds an automated RAUC update client that polls a remote URL for new bundles on a configurable timer.

meta-moonforge-rauc-update provides a lightweight systemd service that periodically checks a configured URL for a new RAUC bundle and applies it automatically. It is designed to complement meta-moonforge-rauc, which handles the low-level bundle verification and partition switching.

What it does

Provides a custom rauc-update.service systemd unit that downloads and installs a RAUC bundle from a given URL.
Runs on a systemd timer, so that devices check for updates automatically at regular intervals without any operator intervention.
Optionally forces a reboot immediately after a successful update, so that the new slot is activated as soon as possible.

Why use it

For products that need a simple, fire-and-forget update mechanism, where devices should just stay current without requiring any fleet management infrastructure, this layer provides a minimal but functional solution out of the box. More sophisticated update orchestration (staged rollouts, canary deployments, rollback policies) can be layered on top by replacing or wrapping the service from a downstream layer.

Dependencies

meta-moonforge-distro, required by all layers.
meta-moonforge-rauc, the RAUC daemon must be present for the update client to drive.

How to use it

header:
  version: 16
  includes:
    - repo: meta-moonforge
      file: kas/include/layer/meta-moonforge-distro.yml
    - repo: meta-moonforge
      file: kas/include/layer/meta-moonforge-rauc.yml
    - repo: meta-moonforge
      file: kas/include/layer/meta-moonforge-rauc-update.yml

local_conf_header:
  40_meta-moonforge-rauc-update: |
    # URL where the device will look for the latest RAUC bundle.
    RAUC_BUNDLE_URL = "https://updates.example.com/LATEST.raucb"
    # Set to "1" to reboot immediately after a successful update.
    RAUC_FORCE_REBOOT_ON_UPDATE = "1"

Configuration variables

Variable	Required	Description
`RAUC_BUNDLE_URL`	Yes	Full URL to the RAUC bundle file (`.raucb`)
`RAUC_FORCE_REBOOT_ON_UPDATE`	No	Set to `"1"` to reboot after a successful update

Note: When RAUC_FORCE_REBOOT_ON_UPDATE is "1", any application running on the device will be terminated abruptly at reboot time. Applications that cannot tolerate sudden shutdown should register systemd inhibitor locks or listen for the PrepareForShutdown signal to perform a clean shutdown sequence.

Testing locally with a QEMU instance

This walkthrough tests a full update cycle using QEMU and a local HTTP server.

Step 1: Build the initial image and bundle:

$ kas-container build kas/moonforge-image-full-qemux86-64.yml

Step 2: Serve the bundle from a local HTTP server:

$ cd meta-moonforge-rauc-update/backend
$ cp ../../build/tmp/deploy/images/qemux86-64/moonforge-bundle-base-qemux86-64.raucb \
    data/LATEST.raucb
$ podman compose up -d

This server listens on port 3333 of the host. Inside a QEMU instance launched with slirp networking, the host should be reachable at 10.0.2.2.

Step 3: Update the kas configuration to point at the local server:

local_conf_header:
  40_meta-moonforge-rauc-update: |
    RAUC_BUNDLE_URL = "http://10.0.2.2:3333/LATEST.raucb"
    RAUC_FORCE_REBOOT_ON_UPDATE = "1"

Step 4: Boot the image in QEMU and trigger the update:

$ runqemu snapshot kvm nographic slirp ovmf qemux86-64 \
    tmp/deploy/images/qemux86-64/moonforge-image-base-qemux86-64.rootfs.wic

Once logged in, manually start the update service and observe the output:

$ systemctl start rauc-update.service
$ journalctl -fu rauc-update.service

After the bundle is downloaded and verified, the service will reboot the device. On the next boot, RAUC will switch to the new slot. You can verify this with:

$ rauc status

Step 5: Tear down the local server

$ podman compose down --volumes

See: meta-moonforge-rauc-update on GitHub