3. Perform a [pull request](http://help.github.com/pull-requests/) in github's web interface.
If it is a new feature request, don't start the coding first. Remember to [open an issue](https://guides.github.com/features/issues/) to discuss the new feature.
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.
- **CLEAN_LEVEL** (comma-separated list): defines what should be cleaned. Default value is `"make,debs"` - clean sources and remove all packages. Changing this option can be useful when rebuilding images or building more than one image
- "make" = execute `make clean` for selected kernel and u-boot sources,
- "images" = delete `output/images` (complete OS images),
- set to "yes" will prompt you right before the compilation starts to make changes to the source code. Separate for u-boot and kernel. It will also create a patch out of this. If you want that this patch is included in the normal run, you need to copy it to appropriate directory
- **BRANCH** (default|next|dev): you can set kernel and u-boot branch manually to skip dialog prompt; some options may not be available for all devices
- **RELEASE** (wheezy|jessie|trusty|xenial): you can set OS release manually to skip dialog prompt; use this option with `KERNEL_ONLY=yes` to create board support package
- **PROGRESS_LOG_TO_FILE** (yes|**no**): duplicate output, affected by previous option, to log files `output/debug/*.log`
- **USE_MAINLINE_GOOGLE_MIRROR** (yes|**no**): use `googlesource.com` mirror for downloading mainline kernel sources, may be faster than `git.kernel.org` depending on your location
- **FORCE_USE_RAMDISK** (yes|no): overrides autodetect for using tmpfs in new debootstrap and image creation process. Takes effect only if `EXTENDED_DEBOOTSTRAP` is set to "yes"
- **FIXED_IMAGE_SIZE** (integer): create image file of this size (in megabytes) instead of minimal. Takes effect only if `EXTENDED_DEBOOTSTRAP` is set to "yes"
- **ROOTFS_TYPE** (**ext4**|f2fs|btrfs|nfs|fel): create image with different root filesystems instead of default ext4. Requires setting FIXED_IMAGE_SIZE to actual size of your SD card for F2FS and BTRFS. Takes effect only if `EXTENDED_DEBOOTSTRAP` is set to "yes"
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 file name extension `.patch`. User patches directory structure mirrors directory structure of `lib/patch`. Look for the hint at the beginning of patching process to select proper directory for patches. Example:
Patch with same file name in `userpatches` directory tree substitutes one in `lib/patch`. To _replace_ a patch provided by Armbian maintainers, copy it from `lib/patch` to corresponding directory in `userpatches` and edit it to your needs. To _disable_ a patch, create empty file in corresponding directory in `userpatches`.
If file `userpatches/linux-$KERNELFAMILY-$KERNELBRANCH.config` exists, it will be used instead of default one from `lib/config`. Look for the hint at the beginning of kernel compilation process to select proper config file name. Example:
and place your code here. You may test values of variables noted in the file to use different commands for different configurations. Those commands will be executed in a chroot environment just before closing image.
In case you define `$FIXED_IMAGE_SIZE` at build time the partition containing the rootfs will be made of this size. Default behaviour when this is not defined and `$ROOTFS_TYPE` is set to _ext4_ is to shrink the partition to minimum size at build time and expand it to the card's maximum capacity at boot time (leaving an unpartitioned spare area of ~5% when the size is 4GB or less to help the SD card's controller with wear leveling and garbage collection on old/slow cards).
You can prevent the partition expansion from within `customize-image.sh` by a `touch /root/.no_rootfs_resize` or configure the resize operation by either a percentage or a sector count using `/root/.rootfs_resize` (`50%` will use only half of the card's size if the image size doesn't exceed this or `3887103s` for example will use sector 3887103 as partition end. Values without either `%` or `s` will be ignored)
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:**
BOOTSIZE="16" # FAT boot partition in MB, 0 for none
Note that in this case, all main config options (kernel and uboot source) are covered within FAMILY. Check [configuration.sh](https://github.com/igorpecovnik/lib/blob/master/configuration.sh) for more config options.
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:
When root filesystem is ready we need to install 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.
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.
