Building a custom kernel
This a very quick-and-dirty how-to to build (and customize) a kernel for your bubba 3 device. It also works for bubba 2 providing some small differences I will point out.
OK, but what about compiling modules for this custom kernel? How can one compile and install kernel modules for Bubba 2 or 3 device using this method ( by configuring, compiling on the guest operating system installed on VirtualBox )?
The command 'make modules_install' does not install modules ob Bubba device, but want to install on that guest operating system on the VirtualBox.
Preparing a compilation host
You could compile direclty on the B3 (resp. B2) itself, but it would take HOURS. That's why we will use a host which will be cross-compiling the kernel much quicker. Personnaly I use a virtual host in VirtualBox, but you can use whatever machine/virtualization technology.
The host must run debian squeeze, either i386 or amd64. I will not detail the OS install phase, if you want a custom kernel, you probably know how to do that. Nothing fancy here just a plain debian install. The desktop environment is obviously not needed ;-) .
Installing the compilation tools
After the install is completed, install the compiling tools :
- emdebian cross-compilation toolchain:
apt-get install emdebian-archive-keyring echo "deb http://www.emdebian.org/debian/ squeeze main" > /etc/apt/sources.list.d/emdebian.list apt-get update
For the B3:
apt-get install gcc-4.4-arm-linux-gnueabi
For the B2:
apt-get install gcc-4.4-powerpc-linux-gnu
Note: you can install both toolchains if you have both platforms as I do :-)
- native compiler and debian package utils :
apt-get install build-essential devscripts
- platform specific tools :
apt-get install device-tree-compiler uboot-mkimage
- development files for ncurses :
apt-get install libncurses5-dev
Build a custom kernel
Download and prepare the excito kernel source
The next operations can be done as a regular user.
- Prepare the environment :
- For the B3:
export ARCH=arm export CROSS_COMPILE=arm-linux-gnueabi-
- For the B2:
export ARCH=powerpc export CROSS_COMPILE=powerpc-linux-gnu-
- Download the source files
Note: the above link will work as long as excito does not upgrade the kernel.
Customizing the kernel
Now everything is in place, time to customize the kernel:
- Move into the source directory :
- Run the curses-based configuration tool (if you wish to use xconfig, be my guest, there are a few more dependencies to install):
- Load the default excito configuration: From the menu, select Load an Alternate Configuration File and enter the following path:
For the B2:
- From now on you can customize the configuration to suit your needs (even patch the source if you're in the mood ...).
- When you're satisfied, you may exit and save the configuration (it will be written in the path loaded above).
Note: whenever you customize the kernel, the resulting configuration must be placed in arch/arm/configs/bubba3_defconfig (arch/powerpc/configs/bubbatwo_defconfig for the B2); only this file will be used during the compilation phase to configure the kernel.
Compiling and packaging
From the same directory, build the debian package:
dpkg-buildpackage -us -uc -b -aarmel
Note: If anyone knows the distinction between arm and armel, and why it's used here and not there, I'm very much interested !
For the B2 :
dpkg-buildpackage -us -uc -b -apowerpc
The resulting package will be found in the parent directory, bubba3-kernel_188.8.131.52-13_armel.deb or bubba3-kernel_184.108.40.206-13_powerpc.deb
But how can one compiling and packaging kernel modules?
Installing the new kernel on the device
Now you can send the debian package to your device, using scp or whatever you're confortable with. Then install it with a plain:
dpkg -i bubba3-kernel_220.127.116.11-13_armel.deb
(or the obvious adapt for the b2)
You can now reboot your device. If your kernel panics during the boot, use your rescue key to reinstall the original excito kernel from http://b3.update.excito.org/pool/main/l/linux/