Embedded Recipes 2019 - Remote update adventures with RAUC, Yocto and Barebox

Remote-update adventures
RAUC, Yocto, Barebox
Embedded Recipes 2019
2019-09-24 – Paris Story, Paris
Patrick Boettcher YAISE

2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
About me
●
Kernel developer since 2004 – (media drivers)
●
Embedded C++, C (mostly Linux and RTOS),
Python, compilers and testing frameworks
●
Freelancer with YAISE

Overview
1- Intro / Starting position
2- Remote update-strategy
3- Remote upgrade-strategy

The project
●
industrialized LORA-gateway (LoRaWan
with 3G/4G
●
special housing and connectors
●
selected Phytec phyCORE-i.MX 6UL
– 512MB RAM
– 512MB NAND
– ARM Cortex A7 – up to 900MHz
●
Phytec provides a customizable Yocto distribution

Phytec’s Yocto Distro
●
2018
●
based on morty (yocto 2.2)
●
using barebox as bootloader
●
device-tree well handled (barebox merges with
dtb and hands all of it to the kernel)
●
no “standard” system-updade mechanism in this
release

System configuration
●
barebox (with built-in-device-tree)
●
barebox-env
●
kernel
●
dtb
●
rootfs-partition (~490MB )
●
system is accessible via remote-ssh-tunnel (initiated
by the system, via the WAN connection)

What happened?
●
June 2018: first 100 devices have been delivered with the
application-layer running nicely
●
September 2018: a software update requires update of the
base-system (kernel and libc)– of course
– tried to do it with opkg/ipk – not satisfying (to be retried)
– decision to study upgrade possibilities
– learned a lot during #er2018 when discussing with Marek
●
October 2018: Decision-time (customer pays):
– 1st define general update strategy
– 2nd define strategy to update the deployed 100 systems

Basic facts after study - 1
Stick close to what exists and
do not re-invent the wheel, but what does exist?
●
Partitioning (UBI) and filesystem (UBIFS) cannot be
modified from Linux’s user-space running on UBI
●
Putting processes “somewhere else” to change UBI is
complex; barebox can of course do it
●
Barebox has bootchooser
●
Barebox has “state”-partition

Basic facts after study - 2
●
Barebox has a filesystem inside its environment
●
Barebox is self-updatable
●
Barebox’ environment can be accessed from
Linux’s user-space
●
Robust Auto-Update Controller (RAUC) with signed
bundles exists and works
●
Newer versions of Phytec’s Distro use all this, but
do not support Morty

New partitioning (schema!)
●
barebox (with built-in-device-tree)
●
barebox-env
●
rescue-initramfs (46M)
●
rescue-dtb (512K)
●
system0/1: kernel (9M), dtb (512K), rootfs (210M)

Reconfiguring barebox
●
Add bootchooser-functionality (default: 3 attempts per
system, then rescue)
●
Add state-functionality to device-tree (stored in
eeprom)
●
Add format and flash-scripts to defaultenv
●
Add boot-scripts to defaultenv
●
Build barebox-target-tools to rootfs
●
barebox_2017.04.0-phy3.bbappend / state-eeprom.dts

RAUC - bundle
●
Add meta-rauc
– provides “bundle-class”
– provides user-space tools and config-base
●
In your layer add a bundle-file and a .bbappend
for certs and config
●
bitbake <bundle-file-target> meli-bundle.bb

RAUC – bootchooser - demo

Blind upgrade strategy
●
How to convert a remote system from a single-
system-installation to dual-installation?
●
Simple:
– Copy new-barebox, kernel, dtb, rootfs to the rootfs (scp)
– Instrument barebox from userspace (bareboxenv)
– Reboot
– Meditation during 3 minutes
– ssh-reverse-tunnel is apprearing

Blind time- 1
●
user-space
– injects a script to barebox which is executed at boot
– reboot
●
in old-barebox:
– script: mount rootfs, update-barebox if image present
– reset

Blind time- 2
●
in new-barebox:
– script mounts rootfs, copies images if present
– copy some specific config-files to backup-dir in barebox-env
– repartitioning
– flash rootfs, kernel, dtb
– resets state, bootchooser
– self-destruction
– reset
●
in new-linux
– first-boot: config-files are extracted from backup-dir barebox-env
– everything works – ssh-tunnel appears

Success
●
All remotely deployed devices have been
upgraded successfully to date

Oh well
●
Rescue system had no functionality – the idea
was: we’ll get to it later
– 25 systems failed over to rescue system because of
power-supply-variation during kernel boot
●
SSL certificate was valid for one year only. No
certificate infrastructure present for this project
– Update installs a certificate with 100 years validity

Questions?
@PatBoeFra
https://github.com/pboettch
https://yai.se/
p@yai.se

Embedded Recipes 2019 - Remote update adventures with RAUC, Yocto and Barebox

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Embedded Recipes 2019 - Remote update adventures with RAUC, Yocto and Barebox