You will need to setup development environment within [Ubuntu 14.04 LTS x64 server image](http://releases.ubuntu.com/14.04/) and cca. 20G of free space.
- downloads proven sources, applies patches and uses tested configurations,
- cross-compiles universal boot loader (u-boot), kernel and other tools and drivers,
- packs kernel, uboot, dtb and root customizations into debs,
- debootstraps minimalistic Debian Wheezy, Jessie and Ubuntu Trusty into SD card image,
- installs additional packets, applies customizations and shrinks image to its actual size.
Options clarification:
- **KERNEL_ONLY** (yes|no): if we want to compile kernel, u-boot, headers and dtbs package only
- **KERNEL_CONFIGURE** (yes|no): will bring up kernel configurator otherwise kernel will be compiled with script presets located in lib/config/linux-*.config
- **CLEAN_LEVEL** (comma-separated list): defines what should be cleaned. This is useful when we are rebuilding images or building more than one image
- "make" = make clean for selected kernel and u-boot,
- "images" = delete "./output/images",
- "debs" = delete "./output/debs",
- "cache" = delete "./output/cache",
- "sources" = delete "./sources"
- **AFTERINSTALL** (string): is a variable with command executed in a process of building just before closing image to insert some of your custom applications or fixes
- **KERNEL\_KEEP\_CONFIG** (yes|no): overwrite or keep kernel config before compilation
- **USE_CCACHE** (yes|no): use a C compiler cache to speed up the build process
- **BUILD_DESKTOP** (yes|no): builds a desktop on the top of the system with hw acceleration for some boards.
- **FBTFT** (yes|no): is a [driver for small displays](https://github.com/notro/fbtft). Only applicable for old kernels (3.4-3.14)
- **EXTERNAL** (yes|no): compiles custom drivers
- **FORCE_CHECKOUT** (yes|no): ignore manual changes to source
- **BUILD_ALL** (yes|no): cycle through all available board and kernel configurations and make images for all combinations
Some hidden options:
- **PROGRESS_DISPLAY** (none|plain|dialog): way to display output of verbose processes - compilation, packaging, debootstrap
- **PROGRESS_LOG_TO_FILE** (yes|no): duplicate output, affected by previous option, to log file (./output/debug/*.log)
- **USE_MAINLINE_GOOGLE_MIRROR** (yes|no): use googlesource.com mirror for downloading mainline kernel sources, may be faster or slower than git.kernel.org depending on your location
- **BOARD** (string): you can set name of board manually to skip dialog prompt
- **BRANCH** (default|next|dev): you can set kernel and u-boot branch manually to skip dialog prompt; some option may not be available for all devices
- **RELEASE** (wheezy|jessie|trusty): you can set OS release manually to skip dialog prompt; use this option with KERNEL_ONLY=yes to create board support package
## Using command line parameters ##
Instead of editing compile.sh to set options, you can set them by supplying command line parameters to compile.sh
At first run we are downloading all necessary dependencies.
## Using board configuration ##
We need to get some predefined variables about selected 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, ...
**Board configuration example:**
REVISION="1.1" # Version number is altered by board maintainer
BOOTSIZE="16" # FAT boot partition in MB, 0 for none
LINUXSOURCE="linux-neo" # Local folder where to download it
LINUXFAMILY="udoo" # boards share kernel
This **isn't ment to be user configurable** but you can alter variables if you know what you are doing.
## Downloading sources ##
When we know where are the sources and where they need to be the download / update process starts. This might take from several minutes to several hours.
## Patching ##
In patching process we are appling patches to sources. The process is defined in:
lib/patching.sh
## User patching ##
You can add your own patches outside build script. Place your patches inside appropriate directory, for kernel or u-boot. There are no limitations except all patches must have ending **.patch**
userpatches/kernel
userpatches/u-boot
## Compiling or choosing from cache ##
- compile from scratch with additional source cleaning and menu config.
- select cached / already made kernel
## Debootstrap ##
Debootstrap creates fresh Debian / Ubuntu root filesystem templates or use cached under:
output/cache/rootfs/$DISTRIBUTION.tgz
To recreate those files you need to remove them manually.
## Kernel install ##
When root filesystem is ready we need to instal kernel image with modules, board definitions, 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.
## Distribution fixes ##
Each distributin has it's own way of doing things:
- serial console
- different packets
- configuration locations
## Board fixes ##
Each board has their own tricks: **different device names, firmware loaders, configuration (de)compilers, hardware configurators**
## Desktop installation ##
You can build a desktop withing the image. Consider this feature as experimental. Hardware acceleration on Allwinner boards is working within kernel 3.4.x only.
## External applications ##
This place is reserved for custom applications. There is one example of application - USB redirector.
## Closing image ##
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.
