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The Linux 2.6 Kernel Trilogy Ends: Go Configure
Posted by admin on November 28 2006 19:55:25

When we last talked about Linux 2.6 Kernel we left off at giving our new 2.6 kernel a unique name, so we can tell it apart from our other kernels. In our third, and final, salute to the new kernel, we'll get into the gnarly part — configuration (and we'll also cover patching kernels, so you'll know how to keep your new kernels up-to-date).

Configuration is the most tedious, time-consuming part of the process. Howerver, it's extremely important, so don't gloss over it. If you leave things out, you'll have to go through all this again.

Now you may think of yourself an old Linux pro, but the steps for building a 2.6 kernel are different than 2.4, so pay attention.

Before we leap into the fun stuff, we need to review a couple of items from Part 1 of our trilogy. Remember the command for unpacking the compressed kernel archive:

$ bzcat linux-2.6.3.tar.bz2 | tar -xvf -

Yes, this is the olden way, as a kind reader pointed out. Use it if you have an elderly tar that does not support bzip2 archives. Modern editions of tar support bzip2 directly. The modern way:

$ tar xvjf linux-2.6.3.tar.bz2

Part 1 says to use gcc 2.95.3. I have received reports of using gcc versions up to 3.3 successfully. Your mileage may vary.

The Steps So Far

1. Obtain kernel source code, and download it into ~/src

2. Make sure gcc, GNU make, binutils, util-linux, and module-init-tools are up-to-date

3. Make hard copies of dmesg, lscpi, and lsusb

4. Backup any existing .config file (there may not be one)

5. Run make mrproper to restore the source directory to a pristine state

6. Edit ../linux-2.6.3/Makefile to give the new kernel a unique name, like EXTRAVERSION =new-name

module-init-tools replaces modutils in the 2.6 kernel. You can have both on your system. And, in addition to being well-armed with printouts of lscpi and dmesg, it is also wise to capture lsusb:

$ lsusb -v | lpr

lsusb is part of usbutils.

Configuration
This is the most tedious, time-consuming part. Howerver, it's extremely important, so don't gloss over it. If you leave things out, you'll have to go through all this again. It is tempting to recycle your 2.4 .config, and run make oldconfig, but don't. The 2.4 and 2.6 kernels are quite different, this is asking for trouble.

Configure From Scratch
There are two nice graphical configuration utilities: menuconfig, and xconfig. menuconfig is ncurses-based, so you don't need X. xconfig in 2.6 requires Qt and X. Let's use xconfig, because it is sleek and fast, and completely redesigned for 2.6:

$ make xconfig

This will putter and mutter for a bit, then spit out a menu. Have your printouts handy, because now you have to select the right drivers for your hardware, decide what features your kernel will have, and whether to load drivers as modules, or build them into the kernel. menuconfig and xconfig generate loads of information — read all of it. Many things will be selected by default. The worst thing that can happen by saying "yes" too many times is you'll enable features that won't be used. This is not a bad thing. In contrast, if you leave something out that you need, you may need to rebuild the kernel. Here are few things which should be built into the kernel:

module support

a.out binaries, ELF binaries, and MISC binaries

VGA text console

All filesystems you'll be using, such as ext2/3, ReiserFS, JFS, XFS, loopback, vfat, NTFS, udf, etc.

These depend on your hardware; whatever you select should be built into the kernel, not a loadable module:

IDE, ATA, and ATAPI Block Devices

SCSI support (note that the 2.6 kernel does not need IDE-SCSI, so if you have no SCSI devices, you can omit this)

USB support

Any on-board controllers

Sound support

These are OK to have as loadable modules:

NIC drivers

Netfilter/iptables

USB drivers

sound card drivers

There are help files on almost every item.

By Carla Schroder

http://www.enterprisenetworkingplanet.com