This buildroot fork will produce a kernel and rootfs with many useful features for the Raspberry Pi, yet with a very quick boot (about 5 s). It's intended for advanced users and specific embedded applications.
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If you're not familiar with Buildroot and what it can and can't do, please take the time to read the manual.
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You must be pretty comfortable with cross-compilation in order to use rpi-buildroot.
It is recommended to use rpi-buildroot with the default toolchain for Raspberry Pi:
# The '-x64' suffix must be removed for 32-bit build machines.
svn export https://github.com/raspberrypi/tools/trunk/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64
export PATH="$(readlink -qsne "gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/"):${PATH}"
arm-linux-gnueabihf-gcc main.c # example usage
git clone --depth 1 git://github.com/ADVANSEE/rpi-buildroot.git
cd rpi-buildroot
make raspberrypi_defconfig
make nconfig # if you want to add packages or fiddle around with it
make # build (NOTICE: Don't use the **-j** switch, it's set to auto-detect)
rpi-buildroot includes a script that can alter a previously generated SD card image. This can be useful e.g. to add a binary file built outside BuildRoot, or to tweak some configuration files without rebuilding the whole image if the build files have not been kept. E.g.:
# This script uses `sudo`, so the user may be asked for a password.
board/raspberrypi/alter-img /path/to/sdcard.img /path/to/sub-script
A sample sub-script that would create a /test file on the rootfs partition could contain:
sudo touch "${parts[1]}/test"
In order to get the help message giving all the details, just run alter-img without any argument.
rpi-buildroot includes a script that can automatically flash your sdcard, you simply need to point it to the correct device node, confirm and you're done!
Notice you will need to replace sdx in the following commands with the actual device node for your sdcard.
# run the following as root (sudo)
board/raspberrypi/mksdcard /dev/sdx
You will need to create two partitions in your sdcard, the first (boot) needs to be a small W95 FAT16 (LBA) patition (that's partition id e), about 32 MB will do.
Notice you will need to replace sdx in the following commands with the actual device node for your sdcard.
Create the partitions on the SD card. Run the following as root. Notice all data on the SD card will be lost.
fdisk /dev/sdx
> p # prints partition table
> d # repeat until all partitions are deleted
> n # create a new partition
> p # create primary
> 1 # make it the first partition
> <enter> # use the default sector
> +32M # create a boot partition with 32MB of space
> n # create rootfs partition
> p
> 2
> <enter>
> <enter> # fill the remaining disk, adjust size to fit your needs
> p # double check everything looks right
> w # write partition table to disk.
Now format the boot partition as FAT 16
# run the following as root
mkfs.vfat -F16 -n boot /dev/sdx1
mkdir -p /media/boot
mount /dev/sdx1 /media/boot
You will need to copy all the files in output/target/boot to your boot partition.
# run the following as root
cp output/target/boot/* /media/boot
umount /media/boot
The second (rootfs) can be as big as you want, but with a 200 MB minimum, and formated as ext4.
# run the following as root
mkfs.ext4 -L rootfs /dev/sdx2
mkdir -p /media/rootfs
mount /dev/sdx2 /media/rootfs
You will need to extract output/images/rootfs.tar onto the partition, as root.
# run the following as root
tar -xvpsf output/images/rootfs.tar -C /media/rootfs # replace with your mount directory
umount /media/rootfs
Insert the flashed SD card into the Raspberry Pi's slot, then power it on.
The default user and password are root and rpi.