As mentioned in a previous post, if you follow the recommendations for setting up and building OE, the bitbake process cleans up after itself and you can not make in-place modifications to the kernel source. Granted it is preferable to setup a local overlay in which to do all your work, but it you just want to make a quick change and test it, this process will save you a little time.
After setting up the OE environment (and building everything once to make sure your environment is configured correctly, see Building OpenEmbedded for BeagleBoard and Building Angstrom…) do the following:
$ cd ${OETREE}/build
$ bitbake -c clean linux-omap-2.6.28
$ bitbake -f -c compile linux-omap-2.6.28
The above commands will clean and build a fresh copy of the kernel, leaving the sources in place for future use; you can find them here:
$ cd ${OETREE}/angstrom-dev/work/beagleboard-angstrom-linux-gnueabi/linux-omap-2.6.28-r18/git
$ ls
COPYING Makefile arch fs lib samples virt
CREDITS Module.symvers block include mm scripts vmlinux
Documentation README crypto init modules.order security vmlinux.o
Kbuild REPORTING-BUGS drivers ipc net sound
MAINTAINERS System.map firmware kernel patches usr
From here you can reconfigure the kernel. After ensuring ncurses was installed:
$ yum install ncurses-devel
I was able to
$ make menuconfig
and make my modifications. After saving my configuration changes to update the .config file, it was a simple matter of rerunning the forced compile step from above to rebuild the kernel:
$ bitbake -f -c compile linux-omap-2.6.28 $ bitbake -f -c deploy linux-omap-2.6.28
If your kernel configuration modifications happen to result in the generation of any loadable modules, then you will wind up with another file in the deployment images folder:
$ cd ${OETREE}/angstrom-dev/deploy/glibc/images/beagleboard
$ ls mod*
modules-2.6.28-r18-beagleboard.tgz
This file will need to be copied to your SD card and extracted in-place after you’ve extracted the rootfs to the SD card. I use the following script (~/bin/mvrootfs) to accomplish this:
#!/bin/bash
if [ "$(id -u)" != "0" ]; then
echo "This script must be run as root" 1>&2
exit -1
fi
if [ "${#}" != "1" ]; then
echo "usage: $0 sd[x]"
exit -2
fi
source /home/cmma/oe/source-me.txt
DV=/dev/${1}2
ROOTFS=cmma-ptrp-image-beagleboard.tar.bz2
MODULES=modules-2.6.28-r18-beagleboard.tgz
DEST=/media/LABEL2
DEPLOY=${OETREE}/angstrom-dev/deploy/glibc/images/beagleboard
/bin/cp -f ${DEPLOY}/${ROOTFS} ${DEST}
/bin/cp -f ${DEPLOY}/${MODULES} ${DEST}
cd ${DEST}
/bin/tar -jxvf ${ROOTFS} && rm -f ${ROOTFS}
/bin/tar -xvzf ${MODULES} && rm -f ${MODULES}
cd
/bin/sync
/bin/umount /dev/${1}?
Where the name of my image is cmma-ptrp-image, OETREE=/home/cmma/oe and I am using an SD card configured according to these instructions. If my SD card mounts on /dev/sdb, I invoke the script as such:
$ sudo ~/bin/mvrootfs sdb
Then simply put the SD card back in the BeagleBoard and power up.