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.

For PPC64 you should use gentoo-sources.

# emerge gentoo-sources

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 gentoo-sources-. Your version may be different, so keep this in mind.

# ls -l /usr/src/linux
lrwxrwxrwx    1 root    root       12 Aug 10 11:04 /usr/src/linux -> linux-

Now it is time to configure and compile your kernel source. There is the ability to use "genkernel" which would create a generic kernel like the ones used on the installation CDs, but it is not fully functional for PPC64 at the moment.

Continue now with 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 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).

# cd /usr/src/linux
Important: In case you are in 32-bit userland, you must edit the top
level Makefile in /usr/src/linux and change the CROSS_COMPILE option to
CROSS_COMPILE ?= powerpc64-unknown-linux-gnu-. You must do this before you run
make menuconfig or it may result in kernel compilation problems.
# 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).

First 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, and /dev/pts file system for Unix98 PTYs:

File systems --->
  [*] Virtual memory file system support (former shm fs)
  [*] /proc file system support
  [*] /dev/pts file system for Unix98 PTYs

(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 (you will find the mentioned options under Networking support which is a subpart of Device Drivers):

Network device 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 ppp when configured to do kernel mode PPPoE.

If you require it, don't forget to include support in the kernel for your ethernet card.

When you're done configuring your kernel, continue with Compiling and Installing.

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

# make && make modules_install

When the kernel has finished compiling, copy the kernel image to /boot. Remember to replace <kernel-version> with your actual kernel version:

# cp vmlinux /boot/<kernel-version>

Now continue with Configuring the Modules.