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Compiling a new Kernel (and Reiser4).

This is the first of three articles to help you get your favorite Linux distro running on Reiser4 (that is, to get Linux installed, and functional, on a partition formatted with the Reiser4 filesystem). If you are not interested in Reiser4, then this first article, can simply be considered, a guide to recompiling your kernel.

This guide will use the linux-2.6.23 kernel. Download it,

linux-2.6.23.tar.bz2 from

If you are not interested in Reiser4, ignore the commands in blue.

Of course, if you use a different kernel, you will have to change various details.

It is assumed that you are the root user.

Make sure that you have the following programs and packages installed.

For SuSE 10.0: gcc libgcc glibc glibc-devel glib2 glib2-devel ncurses ncurses-devel gcc-c++ libstdc++ libstdc++-devel.

For Debian 4.0-r0 (Etch): emacs21 bzip2 gcc libncurses5-dev (libc6-dev linux-kernel-headers) libc6-dev-i386 (lib32gcc1) g++ (libstdc++6-4.1-dev). The bracketed items are installed automatically when the previous item is installed. The linux-kernel-headers are deceptively named. They are really libc headers and are installed to /usr/include/ (although similar files also occur in the kernel sources).

Download a patch that matches your choice of kernel:

reiser4-for-2.6.20.patch.gz from, local copy here, or
reiser4-for-2.6.21.patch.gz from, local copy here, or
reiser4-for-2.6.22.patch.gz from, local copy here, or
reiser4-for-2.6.23.patch.gz from, local copy here.
reiser4-for-2.6.24.patch.gz from, local copy here.
reiser4-for-2.6.25.patch.bz2 from, local copy here.

Save the patch and linux-2.6.23.tar.bz2 to /usr/src/.

Andrew Morton, also provides a Reiser4 patch in his mm patch-set. There have been significant problems with Morton's Reiser4. It appears that some of the kernel "developers" are actually sabotaging development. For more details, see:

The Linux Kernel Saboteurs.

OK, let's begin. Change to the directory /usr/src/.

 cd /usr/src/

Unpackage everything.

 tar -xf linux-2.6.23.tar.bz2
 bunzip2 reiser4-for-2.6.23.patch.bz2

Change to the new kernel source directory.

 cd /usr/src/linux-2.6.23/

Patch the kernel for the Reiser4 filesystem. You may wish to use the --dry-run option.

 patch -p1 < /usr/src/reiser4-for-2.6.23.patch

Copy a working kernel configuration file to .config with the command:

 cp /boot/config-$(uname -r) /usr/src/linux-2.6.23/.config

The command uname -r gives the kernel version that you are currently using.

To avoid confusion, I will assume that uname -r gives config-2.6.13-15-default for SuSE and config-2.6.18-4-amd64 for Debian. These were the default kernels shipped with the distros:

 cp /boot/config-2.6.13-15-default /usr/src/linux-2.6.23/.config   (SuSE)
 cp /boot/config-2.6.18-4-amd64 /usr/src/linux-2.6.23/.config   (Debian)

Have a look at the available kernel building options, with the command:

 make help

Now run menuconfig (or xconfig or gconfig)

 make menuconfig

On saving, menuconfig will have automatically updated the old .config file, to a current one.

Now make the following changes:

File systems --->
   <*> Reiser4 (EXPERIMENTAL)

<*> means that the feature is compiled into the kernel.
<M> means that the feature is compiled as a module.
<  > means that the feature is ignored.

If you plan to install a Linux distro on a Reiser4 partition, then you must compile it into the kernel. Otherwise, just compile Reiser4 as a module. Building a driver as a module, means that the size of the kernel is only increased when the driver is used. If you plan to use Reiser4 as your main filesystem, then the Reiser4 module will always be loaded anyway, so it may as well be compiled into the kernel.

Both SuSE and Debian have no ATA support in the default kernel configurations, yet the modules needed for ATA support mysteriously turn up in the initrd. This "accident" means, that many who compile their own kernel, will find that it will not boot. You can avoid this trap, by configuring all the Serial ATA and Parallel ATA drivers, as modules.

Device Drivers --->
   Serial ATA (prod) and Parallel ATA (experimental) drivers --->
      <M> configure all 55 drivers on this page as modules
      <M> ------------
      <M> configure all 55 drivers on this page as modules

Of course, if you have no SATA or PATA disks or DVD's, then you can forget this. However, configuring them as modules doesn't hurt, the modules will just not be used, and, if in the future you add such a disk, or DVD, the drivers will be waiting.

If you had been given the real configurations for the old kernels, you would not need to make any alterations to the new configurations (made by "make menuconfig") except to add new features. If you have a recent CPU, one new feature you may be interested in, is the kernel virtual machine support:

Device Drivers --->
   Virtualization --->
      <M> Kernel-based Virtual Machine (KVM) support
      <M> KVM for Intel processors support
      <M> KVM for AMD processors support

If there is any chance of overwriting an old kernel, adjust the "local version" option to avoid this.

General setup --->
   (-my-kernels-name) Local version - append to kernel release

The SuSE configuration adds (-default) here. Debian, adds () nothing. I used ().

Ideally, you should compile all the drivers necessary to boot your system into the kernel (ie, drivers necessary to boot your system should not be built as modules). If you do this you will not need an initrd (initial ram disk) file. However, it is very difficult for someone who is new to compiling kernels, to be able to choose all the right features.

Since I wish this guide to be of use to everyone, I have tried to make it as simple as possible and have included the construction of an initrd file. If you are new to all this, then I suggest you do not compile the drivers (necessary to boot your system) into the kernel. Only, after having successfully built a new kernel and gaining some experience, should you try this. However, even with a little experience, your attempts to compile in all the necessary drivers, will often be rewarded with kernels that refuse to boot.

After adding any other interesting features that seem desirable, you should try to compile the new kernel. If you are using a distribution like SuSE, Mandriva, or Red Hat, you should build an RPM package with the command:

 make binrpm-pkg   which packages just the necessary stuff, or
 make rpm-pkg   which also packages the source code.

This can take quite a while, as we are building a large number of unnecessary (but potentially necessary) modules. When built, the RPM package is put in /usr/src/packages/RPMS/ under your architecture type. You may wish to un-install previous kernel installs, but do NOT un-install your presently working kernel. You must keep this kernel package installed so that you will be able to reboot your system if the new kernel does not work. Install your new kernel package, with:

 rpm -i /usr/src/packages/RPMS/x86_64/kernel-2.6.23-1.x86_64.rpm

You may wish to use the --test option if you are unsure how things will go. This will run through the install process, without actually doing the installing.

If you are using Debian, create a .deb package with:

 make deb-pkg   (Debian)

This can take quite a while. When built, the .deb package is put in /usr/src/. Install the package (you may have to un-install previous installs, but do not un-install your presently working kernel) with:

 dpkg -i /usr/src/linux-2.6.23_2.6.23_amd64.deb

You may wish to use the --dry-run option if you are unsure how things will go.

Un-installing packages is a little unusual, as the installed name is not quite the same as the name of the package you install. Given a package, you can find its installed name with:

rpm -qp --info kernel-2.6.23-1.x86_64.rpm (SuSE, Mandriva, Red Hat, etc)
dpkg --info linux-2.6.23_2.6.23_amd64.deb (Debian)

Once you know the name/version, you can uninstall it with:

rpm -e kernel-2.6.23 (SuSE, Mandriva, Red Hat, etc)
dpkg -P linux-2.6.23 (Debian)

Of course, in Debian you can also use synaptic to uninstall the package.

For distributions not covered so far, use "make tar-pkg" or "make tarbz2-pkg" or build your kernel manually.

 make tarbz2-pkg

To install it, use:

 tar -xf /usr/src/linux-2.6.23/linux-2.6.23.tar.bz2

The main kernel files, before packaging, can be found here:

/usr/src/linux-2.6.23/ (becomes /boot/
/usr/src/linux-2.6.23/.config (becomes /boot/config-2.6.23)
/usr/src/linux-2.6.23/arch/x86_64/boot/bzImage (becomes /boot/vmlinuz-2.6.23)

The modules, pci-tables, etc, are installed to /lib/modules/2.6.23/.

If a certain section of the code does not compile, then return to menuconfig and turn it off in the configuration. Then rerun "make the-pkg." If you absolutely need the feature corresponding to that section, then try a different kernel.

If you decided to compile in, all the drivers you need to boot, then you will NOT need an initrd file. Otherwise, you will need an initrd file. To build it use the command:

 mkinitrd -k vmlinuz-2.6.23 -i initrd-2.6.23   (SuSE)
 update-initramfs -c -k 2.6.23   (Debian)

Note that, if you do not specify a kernel, mkinitrd will make initrd files for all the kernels it finds.

Now you need to reconfigure GRUB. You need to change the menu.lst file.

 emacs /boot/grub/menu.lst &

Do NOT delete your current boot entry. Keep it, so you can still start your system if things go wrong. Cut and paste a copy of it, above the original. Then adjust the copy for the new kernel.

The vga and bootsplash settings (vga=0x317 splash=silent) sometimes cause problems and may be disabled until your new kernel is up and running. After which, you can add them back. Your GRUB entries should look something like:

For SuSE:

title SUSE LINUX -- My New Kernel 2.6.23
  root (hd0,2)
  kernel /boot/linux-2.6.23 root=/dev/hda3 resume=/dev/hda5
  initrd /boot/initrd-2.6.23

title SUSE LINUX 10.0
  root (hd0,2)
  kernel /boot/vmlinuz-2.6.13-15-default root=/dev/hda3 resume=/dev/hda5 vga=0x317 splash=silent
  initrd /boot/initrd

For Debian:

title	Debian GNU/Linux -- My New Kernel 2.6.23
root	(hd0,1)
kernel	/boot/vmlinuz-2.6.23 root=/dev/sda2 ro 
initrd	/boot/initrd.img-2.6.23

title	Debian GNU/Linux, kernel 2.6.18-4-amd64
root	(hd0,1)
kernel	/boot/vmlinuz-2.6.18-4-amd64 root=/dev/sda2 ro 
initrd	/boot/initrd.img-2.6.18-4-amd64

Other distros, are handled similarly. Note that I have Debian on the 2nd partition and SuSE on the 3rd. You will have to adjust the (hd0,1)'s and /dev/sda2's etc, to suit your situation. With the above changes, the new kernel will be listed on the GRUB menu at boot.

If you do not have a NVIDIA or ATI accelerated graphics system, just reboot and see how things are.

Otherwise, before rebooting, you need to take care of these proprietary kernel modules. Unfortunately, I grew tired of ATI Linux drivers that never worked, and no longer have any ATI graphics cards on which to test things out. However, I now have a number of NVIDIA cards and can tell you what needs to be done in this case. First, you need to save your old NVIDIA kernel module, as the new install will delete it (adjust 2.6.13-15-default as necessary):

 cp /lib/modules/2.6.13-15-default/kernel/drivers/video/nvidia.ko /tmp/

 reboot  into single mode. You do this as follows:

When the GRUB boot menu appears:

1) Choose the SUSE/Debian -- My New Kernel 2.6.23 entry by using the arrow keys.
2) Type the letter e (as opposed to the usual return).
3) Use the arrow keys to select the kernel line.
4) Type the letter e (edit) again.
5) Edit the kernel line by adding the word single (or S) at the end.
6) Hit return.
7) Type the letter b (boot).

Of course, you could have temporarily added the word single (or S) in your menu.lst file, instead.

Alternatively, you can just boot as usual. X will not be able to find a suitable kernel module and will dump you into a console.

If your new kernel is OK, you will boot to a console where you can run the NVIDIA install script (which you can download from NVIDIA). See this page for more information.

Change to the directory containing the NVIDIA install script, make it executable and run it with:

 chmod +x
 ./   (note the ./)

Note that does not compile for 2.6.23. Answer all the questions (say you do NOT want to download a module from NVIDIA and that you wish to compile from the kernel sources).

Move the saved NVIDIA kernel module back:

 mv /tmp/nvidia.ko /lib/modules/2.6.13-15-default/kernel/drivers/video/nvidia.ko

You will need this to boot your old kernel into graphics mode.

Now, reboot again and you should have your old system back, but with a brand new Reiser4 understanding kernel.


Of course, to use Reiser4 you also need to download, and compile, the libraries:
libaal-1.0.5.tar.gz, local copy here,
reiser4progs-1.0.6.tar.gz, local copy here,
from Hans Reiser's company,

The 2nd article in the guide to installing Linux on a Reiser4 partition, can be found here.

A previous guide, using the linux-2.6.20 kernel, can be found here.