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 have just the one kernel tree to choose from, mips-sources. Special patches are needed to make certain systems work. The table below displays the USE flags required to enable the patchsets. Note that Indy, Indigo2 (R4k) and Challenge S systems do not require any additional patchsets.

(Substitute cobalt with the appropriate USE flag for your system if required)
# mkdir /etc/portage
# echo "sys-kernel/mips-sources cobalt" >> /etc/portage/package.use

(Unpack & install the kernel sources)
# USE="-doc" emerge mips-sources

(This assumes PORTDIR is in the usual location; /usr/portage)
# rm /etc/make.profile
# ln -s /usr/portage/profiles/default-linux/mips/mips64/2005.0 (or .../mips64/ip28/2005.0)

(Install the 64-bit kernel toolchain)
# emerge gcc-mips64

When you take a look in /usr/src you should see a symlink called linux pointing to your kernel source. In this case, the installed kernel source points to mips-sources-2.4.24. Your version may be different, so keep this in mind.

# ls -l /usr/src/linux
lrwxrwxrwx    1 root     root           12 Oct 13 11:04 /usr/src/linux -> linux-2.6.13.4

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

# rm /usr/src/linux
# cd /usr/src
# ln -s linux-2.6.13.4 linux

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

Previously, we went through the manual configuration of how to set up the kernel sources. This has become impractical with the number of systems we now support. This section details various sources for sample kernel configurations.

Many of the systems supported have sample .configs hiding in amongst the kernel source. Not all systems have configs distributed in this way. Those that do, can be configured using the commands mentioned in the table below.

All of the Gentoo installation images provide a kernel config option as part of the image itself, accessible as /proc/config.gz. This may be used in many cases. It is best though if your kernel source matches closely, the kernel that is currently running. To extract it, simply run it through zcat as shown below.

# zcat /proc/config.gz > .config

As an aid to users in finding working settings, a hardware compatability database was set up. This database lists the support for various MIPS devices, and allows users to contribute kernel configurations that are known to work. The address for this site is http://stuartl.longlandclan.hopto.org/gentoo/mips.

If you find this service useful, you're welcome to contribute your notes and .config files so that others may benefit from your experience. It should be noted however that there is no guarantee that any of the configuration files downloaded from this site will work.

Once you have found a configuration, download it into your kernel source directory, and rename it to .config. From there, you can run make oldconfig to bring everything up to date, and allow you to customise the configuration before compiling.

# cd /usr/src/linux
# cp /path/to/example-config .config
# make oldconfig
(Just press ENTER at each prompt to accept the defaults... we'll customise later)
# make menuconfig

Now that your kernel is configured, it is time to compile and install it. Exit the configuration and start the compilation process:

(For 2.4 kernel only)
# make dep

(2.4 and 2.6 kernels -- compiling natively)
# make vmlinux modules modules_install

(2.4 and 2.6 kernels -- cross-compiling on target machine)
(    Adjust the mips64-unknown-linux-gnu- accordingly    )
# make vmlinux modules modules_install CROSS_COMPILE=mips64-unknown-linux-gnu-

(When compiling on another machine, such as an x86 box... use the)
( following commands to compile the kernel & install modules into)
(  a specific directory to be transferred to the target machine. )
# make vmlinux modules CROSS_COMPILE=mips64-unknown-linux-gnu-
# make modules_install INSTALL_MOD_PATH=/somewhere

# make vmlinux.32
(This will create vmlinux.32 -- which is your final kernel)

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

# cp vmlinux /boot/kernel-2.6.13.4

(Cobalt Servers -- Compressing the kernel image)
# gzip -9v /boot/kernel-2.6.13.4

You should list the modules you want automatically loaded in one of the relevant files listed below. You can add extra options to the modules too if you want.

• /etc/modules.autoload.d/kernel-2.4 - Kernel 2.4 only
• /etc/modules.autoload.d/kernel-2.6 - Kernel 2.6 only
• /etc/modules.autoload - All Kernels

Therefore, if you have a kernel module that you want to load -- which is common to both 2.4 and 2.6, then place it in /etc/modules.autoload. Otherwise it can be placed in the appropriate file.

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:

# find /lib/modules/<kernel version>/ -type f -iname '*.o' -or -iname '*.ko'

For instance, to automatically load the 3c59x.o module, edit the appropriate file and enter the module name in it.

# nano -w /etc/modules.autoload.d/kernel-2.4

3c59x

This can be also done in a one-liner:

# echo '3c59x' >> /etc/modules.autoload.d/kernel-2.4
(or kernel-2.6, or /etc/modules.autoload...)

Continue the installation with Configuring your System.