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7. Configuring the Kernel
You first need to select your timezone so that your system knows where it is
located. Look for your timezone in /usr/share/zoneinfo, then make a
symlink to /etc/localtime using ln:
Koodilistaus 1.1: Setting the timezone information
# ls /usr/share/zoneinfo
# ln -sf /usr/share/zoneinfo/GMT /etc/localtime
7.b. Installing the Sources
Choosing a Kernel
The core around which all distributions are built is the Linux kernel. It is the
layer between the user programs and your system hardware. Gentoo provides its
users several possible kernel sources. A full listing with description is
available at the Gentoo Kernel
For PPC you can choose between vanilla-sources and
gentoo-sources (both 2.6 kernels). The latter is available when you
perform a networkless installation. Beside those there is a special
kernel-2.6-patchset for the Pegasos: pegasos-sources. So let's
continue with emerge'ing the kernel sources:
Koodilistaus 2.1: Installing a kernel source
# emerge gentoo-sources
The PowerPC sources are based on a 2.6.10-kernel with security patches from
2.6.11 backported. As the time of the release the 2.6.11 kernel produced
several problems on different PowerPC machines.
When you take a look in /usr/src you should see a symlink called
linux pointing to your kernel source. We will assume the kernel
source installed is gentoo-sources-2.6.10-r8:
Koodilistaus 2.2: Viewing the kernel source symlink
# ls -l /usr/src/linux
lrwxrwxrwx 1 root root 22 Mar 18 16:23 /usr/src/linux -> linux-2.6.10-gentoo-r8
If the symlink doesn't point to the kernel source of your choice (note that
linux-2.6.10-gentoo-r8 is merely an example) you should change it to the
Koodilistaus 2.3: Changing the kernel source symlink
# rm /usr/src/linux
# cd /usr/src
# ln -s linux-2.6.10-gentoo-r8 linux
Now it is time to configure and compile your kernel source. You
can use genkernel for this, which will build a generic kernel as used
by the Installation CD. We explain the "manual" configuration first though, as
it is the best way to optimize your environment.
If you want to manually configure your kernel, continue now with Default: Manual Configuration. If you want to use
genkernel you should read Alternative: Using
7.c. Default: Manual Configuration
Manually configuring a kernel is often seen as the most difficult procedure a
Linux user ever has to perform. Nothing is less true -- after configuring a
couple of kernels you don't even remember that it was difficult ;)
However, one thing is true: you must know your system when you start
configuring a kernel manually. Most information can be gathered by emerging
pciutils (emerge pciutils) which contains lspci. You will now
be able to use lspci within the chrooted environment. You may safely
ignore any pcilib warnings (like pcilib: cannot open
/sys/bus/pci/devices) that lspci throws out. Alternatively, you can run
lspci from a non-chrooted environment. The results are the same.
You can also run lsmod to see what kernel modules the Installation CD
uses (it might provide you with a nice hint on what to enable).
Now go to your kernel source directory and execute make menuconfig. This
will fire up an ncurses-based configuration menu.
Koodilistaus 3.1: Invoking menuconfig
# cd /usr/src/linux
# make menuconfig
You will be greeted with several configuration sections. We'll first list some
options you must activate (otherwise Gentoo will not function, or not function
properly without additional tweaks).
Activating Required Options
First of all, activate the use of development and experimental code/drivers.
You need this, otherwise some very important code/drivers won't show up:
Koodilistaus 3.2: Selecting experimental code/drivers, General setup
Code maturity level options --->
[*] Prompt for development and/or incomplete code/drivers
General setup --->
[*] Support for hot-pluggable devices
Now go to File Systems and select support for the filesystems you use.
Don't compile them as modules, otherwise your Gentoo system will not be
able to mount your partitions. Also select /proc file system and
Virtual memory. Do not select the /dev file system.
Koodilistaus 3.3: Selecting necessary file systems
File systems --->
Pseudo Filesystems --->
[*] /proc file system support
[ ] /dev file system support (OBSOLETE)
[*] Virtual memory file system support (former shm fs)
<*> Reiserfs support
<*> Ext3 journalling file system support
<*> Second extended fs support
<*> XFS filesystem support
If you are using PPPoE to connect to the Internet or you are using a dial-up
modem, you will need the following options in the kernel:
Koodilistaus 3.4: Selecting PPPoE necessary drivers
Device Drivers --->
Networking support --->
<*> PPP (point-to-point protocol) support
<*> PPP support for async serial ports
<*> PPP support for sync tty ports
The two compression options won't harm but are not definitely needed, neither
does the PPP over Ethernet option, that might only be used by
rp-pppoe when configured to do kernel mode PPPoE.
If you require it, don't forget to include support in the kernel for your
Disable ADB raw keycodes:
Koodilistaus 3.5: Disabling ADB raw keycodes
Macintosh Device Drivers --->
[ ] Support for ADB raw keycodes
Also choose the correct RTC support (disable the Enhanced RTC
Koodilistaus 3.6: Activating the correct RTC option
Character devices --->
[ ] Enhanced RTC
General setup --->
[*] Support for /dev/rtc
Users of OldWorld machines will want HFS support so they can copy compiled
kernels to the MacOS partition. This applies also to NewWorld machines as it is
needed for the special Apple_Bootstrap partition:
Koodilistaus 3.7: Activating HFS support
File Systems --->
[*] HFS Support
When you're done configuring your kernel, continue with Compiling and Installing.
Compiling and Installing
Now that your kernel is configured, it is time to compile and install it. Exit
the configuration and run the commands which will compile the kernel:
Koodilistaus 3.8: Compiling the kernel
# make all && make modules_install
When the kernel has finished compiling, copy the kernel image to
/boot (be sure that it is mounted properly on the Pegasos).
Koodilistaus 3.9: Installing the kernel
(Apple/IBM) # cp vmlinux /boot/kernel-2.6.10
(Pegasos) # cp arch/ppc/boot/images/zImage.chrp /boot/kernel-2.6.10
It is also wise to copy over your kernel configuration file to
/boot, just in case :)
Koodilistaus 3.10: Backing up your kernel configuration
# cp .config /boot/config-2.6.10-gentoo-r8
Now continue with Installing Separate Kernel
7.d. Installing Separate Kernel Modules
Configuring the Modules
You should list the modules you want automatically loaded in
You can add extra options to the modules too if you want.
To view all available modules, run the following find command. Don't
forget to substitute "<kernel version>" with the version of the kernel you
Koodilistaus 4.1: Viewing all available modules
# find /lib/modules/<kernel version>/ -type f -iname '*.o' -or -iname '*.ko'
For instance, to automatically load the 3c59x.o module, edit the
kernel-2.6 file and enter the module
name in it.
Koodilistaus 4.2: Editing /etc/modules.autoload.d/kernel-2.6
# nano -w /etc/modules.autoload.d/kernel-2.6
Koodilistaus 4.3: /etc/modules.autoload.d/kernel-2.6
Continue the installation with Configuring
7.e. Alternative: Using genkernel
If you are reading this section, you have chosen to use our genkernel
script to configure your kernel for you.
Now that your kernel source tree is installed, it's now time to compile your
kernel by using our genkernel script to automatically build a kernel for
you. genkernel works by configuring a kernel nearly identically to the
way our Installation CD kernel is configured. This means that when you use
genkernel to build your kernel, your system will generally detect all
your hardware at boot-time, just like our Installation CD does. Because genkernel
doesn't require any manual kernel configuration, it is an ideal solution for
those users who may not be comfortable compiling their own kernels.
Now, let's see how to use genkernel. First, emerge the genkernel ebuild:
Koodilistaus 5.1: Emerging genkernel
# emerge genkernel
Next, copy over the kernel configuration used by the Installation CD to the
location where genkernel looks for the default kernel configuration:
Koodilistaus 5.2: Copying over the Installation CD kernel config
# zcat /proc/config.gz > /usr/share/genkernel/ppc/kernel-config-2.6
Now, compile your kernel sources by running genkernel --udev all.
Be aware though, as genkernel compiles a kernel that supports almost all
hardware, this compilation will take quite a while to finish!
Note that, if your partition where the kernel should be located doesn't use ext2
or ext3 as filesystem you might need to manually configure your kernel using
genkernel --menuconfig all and add support for your filesystem in
the kernel (i.e. not as a module). Users of EVMS2 or LVM2 will probably
want to add --evms2 or --lvm2 as argument as well.
Koodilistaus 5.3: Running genkernel
# genkernel --udev all
Once genkernel completes, a kernel, full set of modules and
initial root disk (initrd) will be created. We will use the kernel
and initrd when configuring a boot loader later in this document. Write
down the names of the kernel and initrd as you will need it when writing
the bootloader configuration file. The initrd will be started immediately after
booting to perform hardware autodetection (just like on the Installation CD)
before your "real" system starts up.
Koodilistaus 5.4: Checking the created kernel image name and initrd
# ls /boot/kernel* /boot/initrd*
If you want your system to be more like the Installation CD you should,
when your Gentoo installation is over, emerge coldplug. While the
initrd autodetects hardware that is needed to boot your system,
coldplug autodetects everything else. coldplug is available as one
of the packages on the Package CD.
Koodilistaus 5.5: Emerging and enabling coldplug
# emerge -k coldplug
# rc-update add coldplug boot
Now continue with Configuring your System.
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