The Raspberry Pi Zero W comes with added wireless LAN and Bluetooth connectivity
compared to Raspberry Pi Zero.
URL: https://www.raspberrypi.org/products/raspberry-pi-zero-w
Wiki:
https://elinux.org/RPi_Hub
Test results
The Raspbian releases in the table below have been tested by the Mender
community. Please update it if you have tested this integration on other
Raspbian releases:
| Rasbian | Build | Runtime |
|---|---|---|
| Raspbian Stretch 2018-11-13 |  |
|
| Raspi OS Buster 2020-05-27 | |
|
Build Means that the image generation completes without errors and outputs
images. Runtime Means that Mender has been verified to work on the board.
Getting started
Prerequisites
- A Linux-based laptop/workstation (Ubuntu has been verified to work)
- You need to install Docker Engine to use
this tutorial
Build Docker image for mender-convert
Open a terminal and clone the mender-convert
repository, e.g.
git clone -b 2.2.1 https://github.com/mendersoftware/mender-convert.git
Enter your mender-convert environment:
cd mender-convert
There is a utility script which can be used to generate the appropriate docker
image to run mender-convert:
./docker-build
This will create a container image you can use to run mender-convert.
Download the latest stable Raspberry Pi raw disk image
Download the raw Raspberry Pi disk image into a subdirectory input:
mkdir -p input
cd input
wget https://downloads.raspberrypi.org/raspbian_lite/images/raspbian_lite-2019-06-24/2019-06-20-raspbian-buster-lite.zip
Extract the raw Raspberry Pi disk image:
unzip 2019-06-20-raspbian-buster-lite.zip && cd ..
Convert the Raspberry Pi disk image to support Mender
With the raw disk image and the container configured above, we can convert the
image.
You can get your Mender Professional tenant token at the My organization page
in Mender Professional.
Configure the Mender client for hosted Mender server:
./scripts/bootstrap-rootfs-overlay-hosted-server.sh \
--output-dir ${PWD}/rootfs_overlay_demo \
--tenant-token "Paste token from Mender Professional"
There are additional scripts in the scripts/ directory to configure with a
local demo server, or production server.
Run mender-convert inside the container by running:
MENDER_ARTIFACT_NAME=release-1 ./docker-mender-convert \
--disk-image input/2019-06-20-raspbian-buster-lite.img \
--config configs/raspberrypi0w_config \
--overlay ${PWD}/rootfs_overlay_demo
Conversion will take 10-15 minutes, depending on your storage and resources
available.
NOTE!
You will need an SD card with an capacity of at least 8GB when using the
default arguments. The SD card layout will be the following using the default
arguments:
| Part | Type | Purpose | Size | Configure size |
|---|---|---|---|---|
| mmcblk0p1 | vfat | Store the bootloader | 44MB | MENDER_BOOT_PART_SIZE_MB |
| mmcblk0p2 | ext4 | Store the root file system and kernel (active) | 3908MB | MENDER_STORAGE_TOTAL_SIZE_MB 1 |
| mmcblk0p3 | ext4 | Store the root file system and kernel (inactive) | 3908MB | MENDER_STORAGE_TOTAL_SIZE_MB 1 |
| mmcblk0p4 | ext4 | Store persistent data, preserved during Mender updates. | 128MB | MENDER_DATA_PART_SIZE_MB 2 |
1. The rootfs partition size is calculated using the
following formula:
(storage-total-size-mb - data-part-size-mb - boot-part-size) / 2
2. You rarely need to adjust the data part size using
MENDER_DATA_PART_SIZE_MB as this will expanded on first boot to occupy the
remaining free blocks of the SD card.
You can read more about the partition layout required for Mender
here
Use the output images
After a successful conversion, the images and artifacts are:
- deploy/raspberrypi-release-1.sdimg.gz
- deploy/raspberrypi-release-1.ext4
- deploy/raspberrypi-release-1.mender
The disk image (with .sdimg.gz suffix) is used to provision the device storage
for devices without Mender running already. You can write write the sdimg.gz
image to an SD card using the following command:
zcat deploy/raspberrypi-release-1.sdimg.gz | sudo dd of=<path to device> bs=4M && sudo sync
Be careful! If you point to the wrong <path to device> when executing the
above command, you risk overwriting your workstationās local or connected
storage devices.
On the other hand, if you already have Mender running on your device and want to
deploy a rootfs update from this conversion, you should use the Mender
Artifact
files, which have .mender suffix. You can either deploy this Artifact in
managed mode with the Mender server or by using the Mender client only in Standalone
deployments. See Mender introduction for an overview.
Boot from the SD card and connect to your Mender server
Ensure your device has Internet connectivity (e.g. through Ethernet cable with
DHCP support).
After provisioning a SD card with the converted disk image (.sdimg) above,
boot your device from it.
After about 10 minutes, you should see your device Pending authorization under
the Devices tab in your Mender server. Authorize your device to join your Mender
server.
You can now deploy software updates to your Raspberry Pi using the Mender
server!
An improved workflow to generate Artifacts
The workflow of using an emulated device works for testing purposes, but it
might have some limitations as we are emulating and not logged in to a real
device or user.
When working with real deployments the recommended workflow is to have one
golden device, that has not been converted to support Mender. On this device
you carry out all the modifications you need, and then use the resulting SD card
to create Mender Artifact files, in summary:
- flash vanilla Rasbian to the SD card
- boot the SD card, log in and make any modifications needed
- copy the SD card into an image on your workstation (e.g. using
dd) - run
mender-convertwith the--disk-imageoption to generate a Mender
Artifact (like above) - upload the Artifact to your Mender server
- deploy it to your devices
Note that your golden device or SD card is not running Mender and is not
modified during deployments. It is simply the āsourceā for generating the
Artifacts that you deploy to the devices in the field.
References
-
The documentation on Building a Mender Debian
image contains more
information about using Mender with the Debian family of distributions. -
The official Mender documentation explains how
Mender works. This is simply a board-specific complement to the official
documentation.
Known issues
raspi-config does not work as expected on a converted image
The raspi-config tool is a small utility that is commonly used on Raspbian to
configure various aspects of the Raspberry Pi hardware and trying to use this
tool on a converted image will not work (by design).
Specifically it relates to fact that we change the mount point of the boot
partition, which on a stock image is mounted at /boot, but on a converted
image it is mounted at /uboot. The raspi-config tool will try to perform
lookups of files in /boot, and this is typically what will fail when trying to
run this tool on a converted image.
The recommend approach is to use the raspi-config utility on the āGolden
Imageā as described in the āAn improved workflow to generate Artifactsā
section above, and not try to modify the converted image as this should be
viewed as a static configuration that you can share across your device fleet.
Boot firmware files
Raspberry Pi boards have a set of boot
firmware files that are located on the vfat boot part, and a selection of these
files are:
bootcode.bin fixup.dat fixup_cd.dat fixup_db.dat
fixup_x.dat start.elf start_cd.elf start_db.elf
start_x.elf
Occasionally there will be changes to the Raspberry Pi software stack that
requires that these files are updated. One example would be a change in the
Linux kernel that relies on functional changes in the boot firmware and in this
case you need to update the boot firmware together with the Linux kernel to get
a functional device.
See this thread
where the limitations of the boot firmware files on Raspberry Pi are discussed.
Because of this limitation certain upgrade paths using Mender might not work
out-of-the box, e.g one known that will not work is:
- Raspbian Stretch 2019-04-08 ā Raspbian Buster 2019-06-20
To support this update path you must update the boot firmware files at the same
time you are updating to Raspbian Buster 2019-06-20. You can utilize
state-scripts for this.
Note that it is unsafe to do update the boot firmware files because there is no
way you can update these files atomically and it is not possible to roll-back in
case you install something that does not boot, which might render your device
unusable without physical intervention.
Devicetree is not updated
To be able to support update of Linux kernel and devicetree, Mender requires
these to be installed in the /boot directory for each rootfs (normally
/dev/mmcblk0p2 and /dev/mmcblk0p3 ). On the other hand, the Raspberry Pi
boot firmware requires that the DTB file is in the same partition as the boot
firmware ( /dev/mmcbl0p1 ) and the config.txt file. For now Mender will not
use the DTB that is delivered with new artifacts and will continue to boot with
the original DTB that was populated using the sdimg file.
Problem using ādtoverlay=pi3-disable-btā
pi3-disable-btdisables the Bluetooth device and restores UART0/ttyAMA0 to
GPIOs 14 and 15. It is also necessary to disable the system service that
initialises the modem so it doesnāt use the UART
There is currently a known issue with above functionality, that is to enable
UART0 on PIN 14 and 15.
It is actually not something that is caused by Mender specifically, but Mender
requires U-boot to be present to support robust features such as roll-back.
U-boot is typically not enabled if you do a stock Raspberry Pi and some people
are often surprised that the Bluetooth UART stopped working when they integrate
Mender .
The problem is in U-boot which does conflicting configuration, and there is a
workaround reported
here and it has been
reported to U-boot but unclear when/if it will be fixed.
If this post was useful to you, please press like, or leave a thank you note to the contributor who put valuable time into this and made it available to you. It will be much appreciated!
You are absolutely right. Should have done better research before prematurely optimizing things that need no optimizationā¦