meta-rauc: A BitBake repository from om26er

The meta-rauc layer provides support for integrating the RAUC update tool into your device.

Please see the corresponding sections below for more information. For a detailed description on steps necessary to integrate RAUC into your project, refer https://rauc.readthedocs.io/en/latest/integration.html.

Dependencies

This layer depends on:

URI: https://github.com/openembedded/bitbake.git
branch: master

URI: https://github.com/openembedded/openembedded-core.git
layers: meta
branch: master

For rauc-hawkbit client:

URI: https://github.com/openembedded/meta-openembedded.git
layers: meta-python
branch: master

For fuse-support in casync (the default):

URI: https://github.com/openembedded/meta-openembedded.git
layers: meta-filesystems
branch: master

Patches

Please submit patches via GitHub pull request on https://github.com/rauc/meta-rauc

Maintainer: Enrico Joerns <ejo@pengutronix.de>

I. Adding the rauc Layer to Your Build

In order to use this layer, you need to make the build system aware of it.

Assuming the rauc layer exists at the top-level of your yocto build tree, you can add it to the build system by adding the location of the rauc layer to bblayers.conf, along with any other layers needed. e.g.:

BBLAYERS ?= " \
  /path/to/yocto/meta \
  /path/to/yocto/meta-poky \
  /path/to/yocto/meta-yocto-bsp \
  /path/to/yocto/meta-rauc \
  "

II. Building RAUC Host Tool

If you only intend to build the RAUC host tool, you may simply run:

bitbake rauc-native

This will place the rauc binary at tmp/deploy/tools/rauc.

If you need to execute the casync host tool manually, you can do this by running:

bitbake casync-native -caddto_recipe_sysroot
oe-run-native casync-native casync --help

III. Adding the RAUC Update Service to Your Device

To prepare your device for using RAUC as its update handler, you have to follow at least the following steps:

Add rauc to DISTRO_FEATURES in your distro (or local) config:
```
DISTRO_FEATURES += "rauc"
```
Add a rauc_%.bbappend in your device-specific (BSP) layer that installs your RAUC system configuration file under /etc/rauc/system.conf. For information on how to write the RAUC update file, please refer to the RAUC user documentation [1]:
```
FILESEXTRAPATHS:prepend := "${THISDIR}/files:"
SRC_URI:append := " file://system.conf"
```
Create a bundle recipe for your device by adding a recipe that inherits the bundle class and adds all desired configuration:
```
inherit bundle

RAUC_BUNDLE_SLOTS = "rootfs"
RAUC_SLOT_rootfs = "my-rootfs-recipe"

RAUC_KEY_FILE = "path/to/development-1.key.pem"
RAUC_CERT_FILE = "path/to/development-1.cert.pem"
```
For information on how to generate and use the key and certificate files, please refer to the RAUC user documentation [1].

For a more detailed explanation on the required and available variables, read the notes in the bundle.bbclass file.
Build a bundle and the rootfs for your device:
```
bitbake my-bundle-recipe
```

Note: If you do not use packagegroup-base, you als need to manually add the rauc package to your systems image recipe:

IMAGE_INSTALL:append = " rauc"

IV. Building The RAUC hawkBit Clients

This layer offers support for two clients that interface between RAUC and the hawkBit deployment server:

rauc-hawkbit (python implementation)
rauc-hawkbit-updater (C implementation)

To use rauc-hawkbit as a standalone service add to your systems image recipe:

IMAGE_INSTALL:append = " rauc-hawkbit-service"

To use it as a python library in your demo application instead, simply add to your recipe:

DEPENDS += "rauc-hawkbit"

To use rauc-hawkbit-updater in your system add to your image recipe:

IMAGE_INSTALL:append = " rauc-hawkbit-updater"

V. Configure Custom Kernel

In order to use RAUC on your system, the kernel must support SquashFS and loop mounts. For the standard yocto kernel, the meta-rauc layer provides a kernel configuration fragment that enables the config options required for this.

If you build your own kernel with a full custom defconfig file, you have to make sure that the options in recipes-kernel/linux/linux-yocto/rauc.cfg are enabled in your configuration, too.

VI. Build RAUC Development Version

Beside the standard release version recipes, the _git variants of RAUC recipes allow to build RAUC from a master branch revision that is newer than the latest release.

This is especially useful for early testing and adaption to upcoming features in RAUC.

By default, the _git recipes are disabled. To enable it, you can set:

RAUC_USE_DEVEL_VERSION = "1"

in your local.conf. Note that this has the same effect as setting DEFAULT_PREFERENCE = "1" for each recipe (target/native/nativesdk) individually.

VII. References

[1]	(1, 2) http://rauc.readthedocs.io/en/latest/

om26er/meta-rauc