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7. Configuring the Kernel


7.a. Timezone

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:

Code Listing 1.1: Setting the timezone information

# ls /usr/share/zoneinfo
(Suppose you want to use GMT)
# 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 Guide.

MIPS-based systems can choose from mips-sources (the default kernel source for the MIPS architecture) and mips-prepatch-sources (prerelease kernel tree).

Choose your kernel source and install it using emerge. Of course substitute with your choice of sources, this is merely an example:

Code Listing 2.1: Installing a kernel source

# emerge mips-sources

When you take a look in /usr/src you should see a symlink called linux pointing to your kernel source:

Code Listing 2.2: Viewing the kernel source symlink

# ls -l /usr/src/linux
lrwxrwxrwx    1 root     root           12 Oct 13 11:04 /usr/src/linux -> linux-2.4.24

If this isn't the case (i.e. the symlink points to a different kernel source) change the symlink before you continue:

Code Listing 2.3: Changing the kernel source symlink

# rm /usr/src/linux
# cd /usr/src
# ln -s linux-2.4.24 linux

Now it is time to configure and compile your kernel source.

7.c. 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 viewing the contents of /proc/pci (or by using lspci if available). You can also run lsmod to see what kernel modules the LiveCD 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.

Code Listing 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:

Code Listing 3.2: Selecting experimental code/drivers

Code maturity level options --->
  [*] Prompt for development and/or incomplete code/drivers

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 Virtual memory, /proc file system, /dev file system + Automatically mount at boot:

Code Listing 3.3: Selecting necessary file systems

(With a 2.4.x kernel)
File systems --->
  [*] Virtual memory file system support (former shm fs)
  [*] /proc file system support
  [*] /dev file system support (EXPERIMENTAL)
  [*]   Automatically mount at boot
  [ ] /dev/pts file system for Unix98 PTYs

(With a 2.6.x kernel)
File systems --->
  Pseudo Filesystems --->
    [*] /proc file system support
    [*] /dev file system support (OBSOLETE)
    [*]   Automatically mount at boot
    [*] Virtual memory file system support (former shm fs)

(Select one or more of the following options as needed by your system)
  <*> Reiserfs support
  <*> Ext3 journalling file system support
  <*> JFS filesystem 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:

Code Listing 3.4: Selecting PPPoE necessary drivers

(With a 2.4.x kernel)
Network device support --->
  <*> PPP (point-to-point protocol) support
  <*>   PPP support for async serial ports
  <*>   PPP support for sync tty ports

(With a 2.6.x kernel)
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 ethernet card.

If you are using an Indy/Indigo2 based system, you need to activate support for it.

Code Listing 3.5: Activating SGI IP22

Machine selection --->
  [*] Support for SGI IP22 (Indy/Indigo2)

If you want to run Irix binaries, include the following option:

Code Listing 3.6: Including IRIX Binary support

General setup --->
  [*] Include IRIX binary compatibility

If you have ISA/EISA cards in your SGI Indigo2, enable support for it.

Code Listing 3.7: Enabling ISA/EISA support for SGI Indigo2

General setup --->
  [*] Indigo-2 (IP22) EISA bus support
  [*]   ISA bus support

If you have a SGI parallel port, you can enable support for it. If you have an ISA parallel port you should select "PC-style hardware" instead.

Code Listing 3.8: Enabling SGI Parallel Port Support

Parallel port support  --->
  <*> Parallel port support
  <*>   SGI Indy/Indigo2 hardware (EXPERIMENTAL) (NEW)
  <*>   IEEE 1284 transfer modes (NEW)

If you want to use the Indigo2 ISA slots, enable the plug and play support.

Code Listing 3.9: Enabling PnP support for ISA

Plug and Play configuration  --->
  <*> Plug and Play support
  <*>   ISA Plug and Play support

Don't forget to enable SCSI support, and use the SGI WD93C93 Driver:

Code Listing 3.10: Enabling WD93C93 Driver Support

SCSI low-level drivers  --->
  <*> SGI WD93C93 SCSI Driver

For network cards you probably need support for the SGI Seeq ethernet controller:

Code Listing 3.11: Enabling SGI Seeq Support

Network device support  --->
  Ethernet (10 or 100Mbit)  --->
    [*] Ethernet (10 or 100Mbit)
    [*]   SGI Seeq ethernet controller support

Don't forget to enable serial console support and enable support for the SGI Zilog85C30:

Code Listing 3.12: Enable SGI Zilog85C30 Support

Character devices --->
  [*] Non-standard serial port support
  [*]   SGI Zilog85C30 serial support

Also don't forget to enable the Indy/I2 Watchdog support as well as the SGI DS1286 RTC support:

Code Listing 3.13: Enable Watchdog and RTC Support

Character Devices --->
  [*] SGI DS1286 RTC support
  Watchdog Cards  --->
    [*] Watchdog Timer Support
    <*>   Indy/I2 Hardware Watchdog

You should also enable support for SGI partitions :)

Code Listing 3.14: Enabling Support for SGI Partitions

File Systems --->
  Partition Types --->
    [*] Advanced partition selection
    [*]   SGI partition support

If you have an SGI Newport (XL Gfx) Card and want to use it, then you'll want to enable support for it:

Code Listing 3.15: Enabling Support for the SGI Newport Card

Console drivers  --->
  <*> SGI Newport Console support (NEW)

If you want sound support on your Indy/Indigo2, enable support for it:

Code Listing 3.16: Enabling Support for the SGI HAL2

Sound  --->
  <*> Sound card support
  <*>   SGI HAL2 sound (EXPERIMENTAL)

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 make dep && make vmlinux modules modules_install:

Code Listing 3.17: Compiling the kernel

(For 2.4 kernel)
# make dep && make vmlinux modules modules_install

(For 2.6 kernel)
# make && make modules_install

When the kernel has finished compiling, copy the kernel image to /boot.

Code Listing 3.18: Installing the kernel

# cp vmlinux /boot/kernel-2.4.24
# cp /boot/

It is also wise to copy over your kernel configuration file to /boot, just in case :)

Code Listing 3.19: Backing up your kernel configuration

# cp .config /boot/config-2.4.24

If your system doesn't boot ELF kernels, compile the kernel using make vmlinux.ecoff instead of make vmlinux. The kernel image will be saved as arch/mips/boot/vmlinux.ecoff instead of vmlinux.

7.d. Installing Separate Kernel Modules

Configuring the Modules

You should list the modules you want automatically loaded in /etc/modules.autoload.d/kernel-2.4 (or kernel-2.6). 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 just compiled:

Code Listing 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-2.4 or kernel-2.6 file and enter the module name in it.

Code Listing 4.2: Editing /etc/modules.autoload.d/kernel-2.4

(Example for 2.4 kernels)
# nano -w /etc/modules.autoload.d/kernel-2.4

Code Listing 4.3: /etc/modules.autoload.d/kernel-2.4 or kernel-2.6


Now run modules-update to commit your changes to the /etc/modules.conf file:

Code Listing 4.4: Running modules-update

# modules-update

Continue the installation with Configuring your System.

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Page updated September 1, 2004

Summary: The Linux kernel is the core of every distribution. This chapter explains how to configure your kernel.

Sven Vermeulen

Daniel Robbins

Chris Houser

Jerry Alexandratos

Seemant Kulleen
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