Articles

Compilation and usage of custom Porteus kernel

Before you start: make a backup of your existing Porteus installation!

WARNING: after upgrading, all kernel dependent Porteus modules like VirtualBox or proprietary GPU drivers will need to be recompiled against the new kernel version too.
WARNING: If you are changing something in the kernel config and recompiling the kernel once again, you may need to replace all of the kernel modules (M) in the ramdisk and 000-kernel.xzm accordingly.

Hardware requirements:
More than 2GB of memory if you are running Porteus with the copy2ram cheatcode and compiling with the sources in your live filesystem, and
1,0GB of free space on your usb stick or hard drive if you are building up a maximum compatibility kernel (i.e., all options enabled), so that you can save your kernel sources.  Note that if you are compiling from within Porteus, it is best to place the source code in your live filesystem (this article uses the /root/ directory) -- however, if you have 2GB of RAM or less and you are compiling a maximum compatibility kernel, it is best to place the source code on a hard drive or usb stick (formatted with a linux filesystem) while it is compiling.  Otherwise, you may run out of room in aufs and your compile will fail.

Let's start:

Section I Kernel

First of all make sure that Porteus development package is activated:

activate /mnt/sdb1/porteus/optional/005-devel.xzm

Download your new kernel version and unpack it somewhere:

wget http://www.kernel.org/pub/linux/kernel/v3.0/linux-3.7.8.tar.xz
tar -xf linux-3.7.8.tar.xz -C /root/

Get the aufs patch (you must have 'git' utility installed on your system) for 3.7.x kernel with script below:

$!/bin/sh

mkdir /tmp/aufs$$
cd /tmp/aufs$$
git clone git://git.code.sf.net/p/aufs/aufs3-standalone aufs3-standalone.git
cd aufs3-standalone.git
# uncomment line below to get aufs for stable kernel
git checkout origin/aufs3.7
# uncomment line below to get aufs for latest -rc kernel
#git checkout origin/aufs3.x-rcN
mkdir ../a ../b
cp -r {Documentation,fs,include} ../b
rm ../b/include/uapi/linux/Kbuild 2>/dev/null || rm ../b/include/linux/Kbuild
cd ..
diff -rupN a/ b/ > /root/linux-3.7.8/aufs.patch

# extra patches:
cat aufs3-standalone.git/*.patch >> /root/linux-3.7.8/aufs.patch

# cleanup:
rm -r /tmp/aufs$$

(in case of using different kernel version plase change 'git checkout origin/aufs3.7' command to for example 'git checkout origin/aufs3.9')

Patch the kernel:

cd /root/linux-3.7.8
patch -p1 < aufs.patch

Once you have the kernel patched, you need to configure it. The best way is to use the old Porteus kernel config file. The configs for Porteus are compiled as a kernel module, so you have to modprobe it and unzip it to the directory where your new kernel sources are before you can apply them:

modprobe configs && zcat /proc/config.gz > .config
make oldconfig

If you are not sure which option to choose, it is best to keep the enter key pressed (default options are usually safe).

Check if your configuration is correct:

make menuconfig

Navigate to "File systems" menu and make sure that FUSE will be compiled in (*). Then go to -> "Miscellaneous filesystems". Aufs and Squashfs must also be compiled in (*), as well as xz compression for Squashfs (*)

Make sure that kernel supports initrd compressed with xz.
Mark other drivers and features as you like

Now it's time to build a kernel, so:

make && make modules_install && make firmware_install

It's going to take a long time, so you'd better grab a beer 

(Note:  If you have a dual core processor, you can run this with 'make -j3' to speed things up a bit)

If no errors are reported you can copy your shiny new kernel to the Porteus /boot directory:

cp arch/x86/boot/bzImage /mnt/sdb1/boot/syslinux/vmlinuz

Comments:

1. It's a good idea it to store your compiled sources somewhere (it's around 1GB when uncompressed), in case you need to add or change something.  If you have a backup you won't have to go through the whole process once again, and compilation will be much faster.
2. If you use Porteus on different machines try to compile as many drivers as possible as modules (M), so the kernel won't be so bloated (my gentoo kernel is only 2MB when stripped to the maximum)
3. The best place for compilation is RAM (fastest). Boot porteus without changes= cheatcode or use tmpfs instead: http://en.wikipedia.org/wiki/Tmpfs

Section II Updating 000-kernel.xzm module with new drivers

Now we need to get rid of the old drivers from 000-kernel.xzm, so:

cp -r /mnt/live/memory/images/000-kernel.xzm/ /root/000-kernel
rm -r /root/000-kernel/lib/modules/*
rm -r /root/000-kernel/lib/firmware/*
cp -r /mnt/live/memory/changes/lib/firmware /root/000-kernel/lib
cp -r /mnt/live/memory/changes/lib/modules/your-new-kernel-version /root/000-kernel/lib/modules
rm /mnt/sdb1/porteus/base/000-kernel.xzm
dir2xzm /root/000-kernel/ /mnt/sdb1/porteus/base/000-kernel.xzm

Reboot and enjoy the new kernel :)

Section III Updating initial ramdisk for pxe boot

To create new initrdpxe.xz please use following script:

#!/bin/sh

cd `pwd`
mkdir pxe
cd pxe
cp -a --parents /lib/modules/`uname -r`/kernel/drivers/net/ethernet .
for x in dca mii libphy sungem_phy ssb uio crc-ccitt; do
  pth="/lib/modules/`uname -r`/$(grep $x.ko: /lib/modules/`uname -r`/modules.dep | cut -d: -f1)"
  cp -a --parents $pth .
done
depmod -b .
find | cpio -H newc -o | xz --check=crc32 --x86 --lzma2 > ../../initrdpxe.xz
cd ..
rm -r pxe
mv ../initrdpxe.xz .
mv /root/initrd.xz /mnt/sdb1/boot/syslinux/pxelinux.cfg/initrdpxe.xz

Good luck!