Yoe Embedded Linux Distribution

Yoe is an Embedded Linux Distribution optimized for product development. It is built on Yocto and OpenEmbedded with a focus on simplicity. This distribution does not end at demo images but rather begins there.

Example

This following is example of building and installing a linux system from scratch on a Raspberry PI 3:

Install Pre-requisites

Install docker on host distribution

• debian-like systems - sudo apt install docker
• RPM based systems - sudo dnf install docker
• Archlinux based systems - sudo pacman -S docker

Add yourself to the docker group:

• sudo gpasswd -a $USER docker
• log out and log back in

Install nftable version of iptables on host distribution this is needed for VNC port forwarding to work on docker

• Archlinux based sytems - sudo pacman -S iptables-nft

• On host systems with 8G RAM or less it will be necessary to ensure a swap file of 8G.

Workspace Setup

1. git clone --recurse-submodules -j8 -b master https://github.com/YoeDistro/yoe-distro.git yoe
2. cd yoe
3. . ./raspberrypi3-64-envsetup.sh
4. yoe_setup
5. bitbake yoe-simple-image
6. insert SD card
7. lsblk (note sd card device, and substitute for /dev/sdX below)
8. yoe_install_image /dev/sdX yoe-simple-image
9. optional: configure console for serial port
10. sudo eject /dev/sdX
11. Install SD card in a Raspberry PI and enjoy your new image

Detailed documentation

Vision

There are many Embedded Linux distribution built on top of OpenEmbedded/Yocto. There is the Poky reference distribution. Most SOC and SOM vendors provide a Yocto variant that supports their products (often put together with repo). While these all provide good ways to build demo images, we feel something slightly different is needed for product development. Thus, the following goals:

1. simple: directory layout is logical so it is easy to find things, and tooling is as simple as possible. Emphasis is on logical organization, minimal magic, and good tooling where it makes sense. We try to minimize uneeded indirection or abstraction unless it really adds value.
2. modern: generate a modern Linux root filesystem using the latest technologies.
3. broad platform support: support a range of single board computers (SBC), system on chips (SoC), and system on modules (SOM). You should not have to use a different build system for every SBC/SOC/SOM you might choose to use in your products. Rather, one build system should easily support building images for a number of different targets in one build tree. Most companies support multiple products with SOCs from multiple vendors, thus the build system should be centered around the user's products and software.
4. repeatable: easy to lock down subprojects (layers) to known versions for repeatable builds
5. extendable: simple to modify and add your own custom software, scripts and tooling. The focus is not on hiding or abstracting Yocto functionality, but rather provider simpler and clearer ways to use it.
6. maintainable: product lifecycles run for many years, so we need a solution where we can build images on a number of different hosts as time marches on. We achieve this through a simple and transparent docker wrapper that contains all the host dependencies needed. This wrapper is invisible (the file system still lives on the host), and is optional if you choose not to use it.
7. transparent: we try to use industry standard tools (git, bitbake, etc) where possible and not invent a lot of new tooling that needs to be learned to use the system. As an example, much of the tooling (envsetup.sh) are simple bash functions and are easy to learn from. Using Yoe will teach you about Yocto.
8. minimal: Embedded Linux images can quickly become bloated so we support technologies like musl libc, opkg package manager, etc. where appropriate.

Supported Machines

See the <machine>-envsetup.sh files for examples of machines we regularly test with.

There is also machine specific documentation available.

Additional machines can be added by including appropriate BSP layers.

Using

envsetup.sh

This is where all the magic happens. In general, this build system must be run in a bash shell. To set up the environment, source the following file:

. ./<machine>-envsetup.sh

Or, you can export a MACHINE environment variable, and then source envsetup.sh.

This file will create a bunch of functions in the environment prefixed with yoe_ that can be executed. Type yoe_ to see them.

directories and key files

• build: temporary directory where build actually takes place
• conf: configuration files for the build
• sources: various sources used for the build. The entries in this directory are git submodules. Note, by default, submodules are shallow clones. If you need the the full git history of a submodule, then run git fetch --unshallow in the submodule directory.
• downloads: contains files that are downloaded by various recipes during builds.
• tools: utility scripts
• localconfig.sh: file created by envsetup.sh that contains directory specific variables based on the build system location.
• local.sh: can be used to customize MACHINE, and other variables

building for another machine

• export MACHINE=[my machine]
• bitbake [recipe name]

Layer management

Adding rocko branch of meta-altera layer to layer mix:

yoe_add_layer https://github.com/kraj/meta-altera rocko

Remove meta-altera:

yoe_remove_layer meta-altera

Customizing the distribution

conf/site.conf contains settings that are common for the project. The YOE_PROFILE templates make it easy to select common options.

customizing settings for your build machine

conf/local.conf contains settings that are commonly modified such as parallel build options.

starting a local feed server

Sometimes you want to install packages you build on the target system without building and re-installing the entire rootfs. This can be done using a feed server.

This advantage of a feed server versus scp'ing opkg files to the target and installing manually is that dependencies will automatically get installed. This mechanism is very useful for packages that are only needed occasionally during development (gdb, screen, strace, iperf, etc).

updating the submodules to the latest

Assuming you have a recent version of git, you can make use of the branch values specified in .gitmodules to update each submodule branch to the HEAD of the specified branch:

git submodule update --remote

Support and Contributing

Pull requests are welcome.

For support or to discuss this project, use one of the following options:

• Yoe community forum
• Open a github issue

License

This build system is licensed under the MIT license which is the same license as oe-core, etc. See COPYING.MIT