Kernel/Overview

This document provides an overview on all kernel sources that Gentoo provides through Portage.

Introduction
As with everything else in Gentoo Linux, the philosophy of the Gentoo Kernel team is to give the user as much freedom of choice as possible. If you take a look at the output of emerge -s sources it is easy to see a large variety of kernels to choose from. This document will attempt to give a brief rundown of the goals of each of the patch sets that Gentoo provides and also explain other kernel sources that are available.

Genkernel
genkernel is a kernel toolset that can be used to autodetect hardware and configure the kernel automatically. This is usually recommended for users who do not feel comfortable about compiling a kernel manually.

For more information, please read the Gentoo Linux Genkernel Guide.

General purpose: gentoo-sources
For most users, the kernel is recommended. gentoo-sources is a kernel based on Linux 3.x, lightly patched to fix security problems, kernel bugs, and to increase compatibility with the more uncommon system architectures.

The package absorbs most of the resources of the Gentoo kernel team. They are brought to the user by a group of talented developers, which can count on the expertise of popular kernel hacker Greg Kroah-Hartman, maintainer of udev and responsible for the USB and PCI subsystems of the official Linux kernel.

For servers: hardened-sources
The kernel is based on the official Linux kernel and is targeted at users running Gentoo on server systems. It provides patches for the various sub-projects of Gentoo Hardened (such as support for SELinux and grsecurity), together with stability and security-enhancements. Check http://www.gentoo.org/proj/en/hardened/ for more information.

ck-sources
is Con Kolivas's kernel patch set. This patchset is primarily designed to improve system responsiveness and interactivity and is configurable for varying workloads (from servers to desktops). The patchset includes a different scheduler, BFS, designed to keep systems responsive and smooth even when under heavy load. Support and information is available at http://kernel.kolivas.org and in the  channel on irc.oftc.net.

git-sources
The package tracks daily snapshots of the upstream development kernel tree. These kernels are good for users interested in kernel development or testing. Bug reports should go to the Linux Kernel Bug Tracker or LKML (Linux Kernel Mailing List).

Architecture dependent kernels
and are, as their names suggest, patched to run best on specific architectures. They also contain some of the patches for hardware and features support from the other patch sets mentioned above and below.

Unsupported kernel packages
Now to briefly describe some of the other which scrolled by when the emerge -s sources command was run. Lets take them in alphabetical order. These kernels are provided as a courtesy only — the various patch sets are not supported by the Gentoo kernel team.

pf-sources
The kernel brings together parts of several different kernel patches. It includes the BFS patchset from, the patches, LinuxIMQ, and the BFQ I/O scheduler.

openvz-sources
OpenVZ is a server virtualization solution built on Linux. OpenVZ creates isolated, secure virtual private servers (VPSs) or virtual environments on a single physical server enabling better server utilization and ensuring that applications do not conflict. For more information, see http://www.openvz.org.

tuxonice-sources
The (formerly sys-kernel/suspend2-sources) are patched with both genpatches which includes the patches found in gentoo-sources, and the patches found in TuxOnIce which are an improved implementation of suspend-to-disk for the Linux kernel, formerly known as suspend2.

This kernel is recommended for laptop users who often rely on being able to suspend their laptop and resume work elsewhere.

usermode-sources
usermode-sources are the User Mode Linux kernel patches and can be found in the package. These kernel patches are designed to allow Linux to recursively run within Linux. User Mode Linux is intended for testing and virtual server support. For more information about this amazing tribute to the stability and scalability of Linux, see http://user-mode-linux.sourceforge.net.

For more information on UML and Gentoo, read the Gentoo UML Guide.

vanilla-sources
Many Linux users will probably be familiar with the package. These kernels are copies of the official kernel sources released on http://www.kernel.org/. Please note that the Gentoo kernel team does not patch vanilla-sources at all; they are purely for people who wish to run a completely unmodified Linux kernel. The Gentoo kernel team recommends instead.

Versions of the kernel can be found under this package: 3.x.

aa-sources
aa-sources was a heavily modified kernel with all kinds of patches. The upstream maintainer stopped releasing kernel patchsets and subsequently this package has been removed.

alpha-sources
alpha-sources was a 2.4 kernel with patches applied to improve hardware compatibility for the Alpha architecture. These patches have been developed and are now included in the mainline kernel. Alpha users can run any recent kernel with no need for extra patches.

Architecture dependent kernels
cell-sources was a 2.6 kernel designed to run on the Sony PlayStation 3 game console.

development-sources
development-sources, the official 2.6 kernel from kernel.org, can now be found under the vanilla-sources package.

gentoo-dev-sources
gentoo-dev-sources, a 2.6 kernel patched with bug, security, and stability fixes, can now be found under the gentoo-sources package.

grsec-sources
The grsec-sources kernel source used to be patched with the latest grsecurity updates (grsecurity version 2.0 and up) which included, amongst other security-related patches, support for PaX. Grsecurity patches are included in the hardened-sources kernel, so this package is no longer available in Portage.

hardened-dev-sources
hardened-dev-sources can now be found under the hardened-sources package.

hppa-sources
hppa-sources</tt> was a 2.6 kernel with patches applied to improve hardware compatibility for the HPPA architecture. These patches have been developed and included in the mainline kernel. HPPA users can now run any recent kernel with no need for extra patches.

mm-sources
The mm-sources</tt> were based on vanilla-sources and contained Andrew Morton's patch set. They included the experimental and bleeding-edge features that were going to be included in the official kernel (or were going to be rejected because they set systems on fire!). They were known to be always moving at a fast pace and could change radically from one week to the other; kernel hackers often used mm-sources</tt> as a testing ground for highly experimental stuff. They have since been removed from the Portage tree.

rsbac-dev-sources
The rsbac-dev-sources</tt> kernels can now be found under the package.

rsbac-sources
Back in the days of 2.6-based kernels contained patches to use Rule Set Based Access Controls (RSBAC ). It was removed due to lack of maintainers, but has has magically reappeared with the 3.10 kernel series. Use hardened-sources if you need additional security features.

selinux-sources
selinux-sources</tt>, a 2.4 kernel including lots of security enhancements, has been obsoleted by security development in the 2.6 kernel tree. SELinux functionality can be found in the hardened-sources package.

sh-sources
sh-sources</tt> was a 2.6 kernel with patches applied to improve hardware compatibility for the SuperH architecture. These patches have been developed and included in the mainline kernel. SuperH users can now run any recent kernel with no need for extra patches.

sparc-sources
sparc-sources</tt> was a 2.4 kernel with patches applied to improve hardware compatibility for the SPARC architecture. These patches have been developed and included in the mainline kernel. SPARC users can now run any recent kernel with no need for extra patches.

uclinux-sources
The uclinux-sources</tt> are meant for CPUs without MMUs as well as embedded devices. For more information, see http://www.uclinux.org. Lack of security patches as well as hardware to test on were the reasons this package is no longer found in the Portage tree.

win4lin-sources
win4lin-sources</tt> were patched to support the userland win4lin tools that allowed Linux users to run many Microsoft Windows (TM) applications at almost native speeds. These kernel sources were removed due to security issues.

xen-sources
xen-sources</tt> was a 2.6-based kernel that allowed running multiple operating systems on a single physical system. A user could create virtual environments in which one or more guest operating systems could run on a Xen-powered host operating system.

The xen-sources</tt> patches were incorporated into the mainline Linux kernel as of version 3.0.

For more information on working with Xen and Gentoo, read the Gentoo Xen Guide.

zen-sources
The package is designed for desktop systems. It includes code not found in the mainline kernel. The Zen kernel has patches that add new features, support additional hardware, and contains various tweaks for desktops. The Zen 3.8 kernel series is currently masked in the Portage tree. For more information on the Zen kernel please visit Zen Kernel Live Sources website.

Acknowledgements
We would like to thank the following authors and editors for their contributions to this guide:


 * Sven Vermeulen
 * Brandon Low
 * Daniel Drake
 * Carl Anderson
 * Jorge Paulo
 * Benny Chuang
 * Gregorio Guidi
 * Shyam Mani
 * Joshua Saddler