PandaBoard Ubuntu: How To recompile the Ubuntu kernel on the Pandaboard

Why Build a New kernel?


There are many reasons, I find the most likely one is because some functionality exists in the very latest build but not in the version you are currently running. Also there are build options you might want to change on the current version such as enabling highmem on the current kernel to allow use of the full 1Gb of RAM on the PandaBoard (currently disabled because of compiler segfault issues).

The reasons boil down to trying something new, tweaking something to run better or fixing an error. There are others of course.
Assumptions:

The following assumes you are running Ubuntu natively on a PandaBoard, you have several gigabytes of free space available to the Pandaboard, a reasonably fast Internet connection to the PandaBoard and hours of time to let it compile.



Step 1: Setup

As we will be using recent packages from the repositories it is a good idea to avoid subtle dependency errors by updating the repository lists:

sudo apt-get update

To start with you will need to install the packages which give you all the dependencies for the kernel, open a terminal and type:

sudo apt-get build-dep linux-image-$(uname -r)

This will likely result in a about 500 MB of downloads and about 800 MB of space being used up. It will also take a while (hour) for the process of downloading and installing to complete.


Step2: Download Kernel Sources

Then find a location which has several gigabytes free (I would guess ~2GB is a minimum), chdir into that location and pull down (clone) the kernel source files for the official Ubuntu kernel:

git clone git://kernel.ubuntu.com/ubuntu/ubuntu-maverick.git

This will clone the source files into the current directory.  It will take about half an hour at least, I was able to achieve ~300KB/s from the server.

Now checkout the working directory with:

git checkout -b working origin/ti-omap4

Step2A: Change the Build Configuration Options

This step is purely optional.  If you want to edit the configuration files which control what is included in the built kernel (ie which drivers, which file systems are supported etc) run the following command:

fakeroot debian/rules editconfigs

Step3: Build the Kernel From Source

Then chdir into that directory, into /ubuntu-maverick/ and generate the kernel package with these commands:

fakeroot debian/rules clean


export $(dpkg-architecture -aarmel)


do_tools=false fakeroot debian/rules binary-arch

[You can also try the following:

fakeroot debian/rules clean

dpkg-buildpackage -B -uc -us   ]

This last command will take a significant amount of time (hours), several gigabytes worth of disk space and generate page after page of compilation information.

The final result of this will be many *.deb files in the root directory where you cloned the git repository to.

After a successful build the root level of your kernel directory should have the follow *.deb files in amongst many *.udeb files:

linux-headers-2.6.35-25-omap_2.6.35-25.44_armel.deb
linux-headers-2.6.35-25-versatile_2.6.35-25.44_armel.deb
linux-image-2.6.35-25-omap_2.6.35-25.44_armel.deb
linux-image-2.6.35-25-versatile_2.6.35-25.44_armel.deb
linux-libc-dev_2.6.35-1025.44_armel.deb
linux-tools-2.6.35-25_2.6.35-25.44_armel.deb

Step4: Install the Kernel

Once this process has completed successfully you will need to install the new kernel. To do this you will install the following *.deb files (change for your version):

         linux-headers-2.6.35-903_2.6.35-903.22_armel.deb
         linux-headers-2.6.35-903-omap4_2.6.35-903.22_armel.deb
         linux-image-2.6.35-903-omap4_2.6.35-903.22_armel.deb

It is important to install these deb files in the right order to avoid subtle errors.

To install these *.deb files type the following command, note you will have to change the version numbers if the version numbers in the files names have changed (ie they have to be the same as the files in the directory.

sudo dpkg -i linux-headers-2.6.35-903_2.6.35-903.22_armel.deb
sudo dpkg -i linux-headers-2.6.35-903-omap4_2.6.35-903.22_armel.deb

sudo dpkg -i linux-image-2.6.35-903-omap4_2.6.35-903.22_armel.deb

Each of these commands will take a while to execute (about 20 minutes all up in my experience).

The final step is to copy the kernel to the correct parts of the SD Card so that uBoot can find it on the next bootup.

The command is:

sudo flash-kernel 2.6.35-903-omap4

Now to explain this "sudo flash-kernel" is the command to execute flash-kernel which copies vmlinuz from /boot/ to the boot up file system.

[Lachlan rightly points out: "The "flash-kernel" command writes the uImage, uInitrd and boot.scr files to the boot partition of your SD card, usually /dev/mmcblk0p1."]

Normally it would guess the correct file to copy but in this case we explicitly ask it to copy the file "vmlinuz.2.6.35-903-omap4" by specifying 2.6.35-903-omap4 after the command.

flash-kernel will append the "vmlinuz-" part to the file name and automatically look in /boot/ for it.

Useful Links:

https://help.ubuntu.com/community/Kernel/Compile

http://www.omappedia.com/wiki/Ubuntu_kernel_for_OMAP4