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There were a few minor things I cleaned up along the way, but mostly I tried to stick to just fixing links.
113 lines
4.6 KiB
Markdown
113 lines
4.6 KiB
Markdown
# What happens behind the build process?
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## Build process summary:
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- creates development environment on top of amd64 Ubuntu 20.04 LTS,
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- downloads proven sources, applies patches on top and uses tested configurations,
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- cross-compiles universal boot loader (***U-Boot***), kernel and other tools and drivers,
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- packs kernel, U-Boot, dtb and root customizations into Debian packages,
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- debootstraps minimalistic Debian Buster and Ubuntu Focal into SD card images,
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- installs additional packets, applies customizations and shrinks image to its actual size.
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Check this image [compiling example](https://youtu.be/zeShf12MNLg) with partial cache.
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## Build process details:
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### Creating compile environment
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First things first. All necessary dependencies are downloaded and installed. This happens though both http and torrent network. Btw. having too much unused traffic? [Help us to reduce ours :)](https://forum.armbian.com/topic/4198-seed-our-torrents/)
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### Using board configuration
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We need to get some predefined variables about selected the board. Which kernel & uboot source to use, modules to load, which is the build number, do we need to have a single partition or dual with boot on fat, which extra drivers to compile out of the kernel tree ...
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All this stuff is predefined for each and every single supported board.
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### Downloading sources
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When we know which sources to use and where they need to be the download or updated this process starts. This might take from several minutes to several hours.
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### Patching
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In the patching process we are applying patches to the used sources. The process is - depending on selected board - defined in:
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lib/patch/kernel/sun7i-default
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lib/patch/kernel/sunxi-dev
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...
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lib/patch/u-boot/u-boot-default
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lib/patch/u-boot/u-boot-neo-default
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...
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Patch rules for subdirectories are: **KERNEL_FAMILY-BRANCH** for kernel and **U-BOOT-SOURCE-BRANCH** for U-Boot.
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### Debootstrap
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Debootstrap creates fresh Debian / Ubuntu root filesystem templates or use cached under:
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output/cache/rootfs/
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To recreate those files you need to remove them manually.
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From time to time they will be recreated anyway if Armbian updates their rootfs cache.
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### Kernel install
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When the root filesystem is ready we need to install the kernel image with modules, board definitions and firmwares. Along with this we set the CPU frequency min/max, hostname, modules, network interfaces templates. Here is also the place to install headers and fix + native compile them on the way.
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### Distribution fixes
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Each distribution has it's own way of doing things:
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- serial console
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- different packets
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- configuration locations
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### Board fixes
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Each board has their own tricks: **different device names, firmware loaders, configuration (de)compilers, hardware configurators**
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### Desktop installation
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You can build a desktop environment withing the image. Consider this feature as experimental. Do not expect to have working hardware acceleration since this is a very complicated task and needs individial care for different boards.
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### External applications
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This place is reserved for custom applications. There is one example of application: USB redirector.
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### Closing image
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There is an option to add some extra commands just before closing an image which is also automaticaly shrink to it's actual size with some small reserve.
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### Directory structure
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It will be something like this:
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compile.sh compile execution script
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lib/bin/ blobs, firmwares, static compiled, bootsplash
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lib/config/ kernel, board, u-boot, hostapd, package list
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lib/documentation/ user and developers manual
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lib/patch/ collection of kernel and u-boot patches
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lib/scripts/ firstrun, arm hardware info, firmware loaders
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lib/LICENSE licence description
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lib/README.md quick manual
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lib/common.sh creates environment, compiles, shrink image
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lib/configuration.sh boards presets - kernel source, config, modules, ...
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lib/distributions.sh system specific installation and fixes
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lib/main.sh user input and script calls
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lib/makeboarddeb.sh creates board support package .deb
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lib/repo-update.sh creates and updates your local repository
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lib/repo-show-sh show packets in your local repository
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lib/upgrade.sh script to upgrade older images
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sources/ source code for kernel, uboot and other utilities
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output/repository repository
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output/cache cache for root filesystem and headers compilation
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output/debs deb packeges
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output/images zip packed RAW image
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userpatches/kernel put your kernel patches here
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userpatches/u-boot put your u-boot patches here
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userpatches/ put your kernel config here
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## Additional info
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- [Allwinner SBC community](https://linux-sunxi.org/Main_Page)
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