1.
Remote-update adventures
RAUC, Yocto, Barebox
Embedded Recipes 2019
2019-09-24 – Paris Story, Paris
Patrick Boettcher YAISE

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

3.
2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Overview
1- Intro / Starting position
2- Remote update-strategy
3- Remote upgrade-strategy

4.
2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
The project
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industrialized LORA-gateway (LoRaWan
with 3G/4G
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special housing and connectors
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selected Phytec phyCORE-i.MX 6UL
– 512MB RAM
– 512MB NAND
– ARM Cortex A7 – up to 900MHz
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Phytec provides a customizable Yocto distribution

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Phytec’s Yocto Distro
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2018
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based on morty (yocto 2.2)
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using barebox as bootloader
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device-tree well handled (barebox merges with
dtb and hands all of it to the kernel)
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no “standard” system-updade mechanism in this
release

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
System configuration
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barebox (with built-in-device-tree)
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barebox-env
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kernel
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dtb
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rootfs-partition (~490MB )
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system is accessible via remote-ssh-tunnel (initiated
by the system, via the WAN connection)

7.
2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
What happened?
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June 2018: first 100 devices have been delivered with the
application-layer running nicely
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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
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October 2018: Decision-time (customer pays):
– 1st define general update strategy
– 2nd define strategy to update the deployed 100 systems

8.
2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Overview
1- Intro / Starting position
2- Remote update-strategy
3- Remote upgrade-strategy

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Basic facts after study - 1
Stick close to what exists and
do not re-invent the wheel, but what does exist?
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Partitioning (UBI) and filesystem (UBIFS) cannot be
modified from Linux’s user-space running on UBI
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Putting processes “somewhere else” to change UBI is
complex; barebox can of course do it
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Barebox has bootchooser
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Barebox has “state”-partition

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Basic facts after study - 2
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Barebox has a filesystem inside its environment
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Barebox is self-updatable
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Barebox’ environment can be accessed from
Linux’s user-space
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Robust Auto-Update Controller (RAUC) with signed
bundles exists and works
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Newer versions of Phytec’s Distro use all this, but
do not support Morty

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
New partitioning (schema!)
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barebox (with built-in-device-tree)
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barebox-env
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rescue-initramfs (46M)
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rescue-dtb (512K)
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system0/1: kernel (9M), dtb (512K), rootfs (210M)

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Reconfiguring barebox
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Add bootchooser-functionality (default: 3 attempts per
system, then rescue)
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Add state-functionality to device-tree (stored in
eeprom)
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Add format and flash-scripts to defaultenv
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Add boot-scripts to defaultenv
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Build barebox-target-tools to rootfs
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barebox_2017.04.0-phy3.bbappend / state-eeprom.dts

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
RAUC - bundle
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Add meta-rauc
– provides “bundle-class”
– provides user-space tools and config-base
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In your layer add a bundle-file and a .bbappend
for certs and config
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bitbake <bundle-file-target> meli-bundle.bb

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
RAUC – bootchooser - demo

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Overview
1- Intro / Starting position
2- Remote update-strategy
3- Remote upgrade-strategy

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Blind upgrade strategy
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How to convert a remote system from a single-
system-installation to dual-installation?
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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

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Blind time- 1
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user-space
– injects a script to barebox which is executed at boot
– reboot
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in old-barebox:
– script: mount rootfs, update-barebox if image present
– reset

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Blind time- 2
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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
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in new-linux
– first-boot: config-files are extracted from backup-dir barebox-env
– everything works – ssh-tunnel appears

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Success
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All remotely deployed devices have been
upgraded successfully to date

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2019-09-24 Remote-update adventures - RAUC, Yocto, Barebox
Oh well
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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
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SSL certificate was valid for one year only. No
certificate infrastructure present for this project
– Update installs a certificate with 100 years validity

21.
Questions?
@PatBoeFra
https://github.com/pboettch
https://yai.se/
p@yai.se