Short version: This project takes a Raspbian-lite base image and modifies it into a Open.HD compatible image. For the long version, read on.
In order to be able to run this you need a Debian or Ubuntu Linux machine with 30 Gb free space on the main partition, and with the following packages:
sudo apt-get install unzip curl git qemu qemu-user-static binfmt-support build-essential gcc-arm*If any of the packages fails to install, run apt update prior to the apt-get install command:
sudo apt updateThen git clone this repository to a suitable folder
git clone https://github.com/OpenHD/Open.HD_Image_Builder.git
cd Open.HD_Image_Builderand run:
sudo -s
./build.sh pi stretchThe earlier version of this builder did all of the work from a single script, while that is basically fine, there were some issues with the approach taken:
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After every modification, the entire process needed to be re-run. (Which takes ~2 hours on a decent machine)
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It was hard for new users to find the different steps and where to make additions
The main issue offcourse being the first one. So, on to this, the new and improved 'staged' image builder.
The core concept (and some code) was taken from pi-gen, the Raspbian image generator. Whenever we make a OpenHd image, we basically perform several steps in order:
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Download the Raspbian lite image
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Increase the size of the partition
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Download, patch and compile the Linux kernel
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Update the image with the patched kernel
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Update the image with several apt-get packages
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Copy the OpenHD code onto the image and compile
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Copy several configuration files
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Cleanup
Remember, this was all done in a single script, and an error in the cleanup step basically meant running it all again.
So after thinking about the problem and looking for projects who had tackled this i looked at the actual Raspbian image generator, who’s output serves as our input (the basic Raspbian lite image). The concept used in the Raspbian image generator is dividing the entire creation process in stages, where the output of the previous stage serves as the input of the next. Stages that have been completed can be skipped in a next build.
This concept applies to the OpenHD image creation as well. So i modified the core logic into this system:
This allows us to run the build process once, and when we want to make a change in stage 3, we only run stage 3 and 4 again by removing the SKIP file from the stages/03-Packages and the stages/04-Wifibroadcast folders. The build system will copy the kernel IMAGE.img from stage 2 to stage 3 and re-run all the scripts in stage 3. The resulting image is copied to stage 4 and all those scripts are run. Finally, when there are no more stages, the IMAGE.img from the last stage is copied to the deploy/ezwfb-{date}.img file.
By placing a SKIP file in the stage folder, the entire stage will be skipped by the build system. Please be aware there is no sanity check in place, removing the SKIP file from stage 3 while leaving the SKIP file in stage 4 will produce an image based on the previous run, ignoring the modifications done in step 3.
It is also possible to put a SKIP-IMAGE file into a stage, this will disable any attempt to copy the image from the previous stage. This is mainly used to prevent image copying in stage 00 and 01 where no image is yet available.
Every stage comprises one or more scripts. Scripts need to be named in the format XX-run.sh or XX-run-chroot.sh. The order is determined by the XX part, where any -chroot script is run AFTER the non-chroot script.
chroot? What’s that? Well, it’s a little complex, but basically it allows you to run statements within the image as if you were running the image on an actual Raspberry Pi. This is used to download and install the apt-get packages and several scripts to make the image ready for use with the OpenHD system. Please remember to use sudo in the -chroot scripts where approperiate.