Kernel

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The Linux kernel is the core of the operating system and offers an interface for programs to access the hardware. The kernel contains most of the device drivers.

Installation

USE flags

To create a kernel, it is necessary to install the kernel source code first. The Gentoo recommended kernel sources for a desktop system are, of course, sys-kernel/gentoo-sources. These are maintained by the Gentoo developers, and patched to fix security vulnerabilities, functional problems, as well as to improve compatibility with rare system architectures.

Optional USE flags for sys-kernel/gentoo-sources:
USE flag (what is that?) Default Recommended Description
build No No  !!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used for creating build images and the first half of bootstrapping [make stage1]
deblob No Remove binary blobs from kernel sources to provide libre license compliance.
symlink No Force kernel ebuilds to automatically update the /usr/src/linux symlink

Emerge

Now install sys-kernel/gentoo-sources:

root #emerge --ask sys-kernel/gentoo-sources

Alternative kernels

There are various alternative kernel sources in the Portage tree:

  • sys-kernel/vanilla-sources - The official, non-patched Linux kernel sources. These sources are left as is, they do not contain any additional patches and are therefore not supported by Gentoo support or developers.
  • sys-kernel/hardened-sources - Gentoo sources with security enhancements.

Sources overview

Kernel sources overview
Most, if not all, of the kernel sources packages available in Gentoo are detailed in the kernel sources overview article. Navigate there for further knowledge on specific kernel sources available in the Portage tree.

Searching all alternatives

A full list of kernel sources with short descriptions can be found by searching with emerge:

root #emerge --search sources

Configuration help

Automatic configuration
genkernel is a tool to used to automate the build process of the kernel and initramfs. The goal of genkernel is to help users through the kernel building process.
Manual configuration
Manual configuration enables the user, with some effort, to create a custom-fit kernel configuration.
Gentoo kernel configuration guide
Gentoo's kernel configuration guide.
Upgrade
Steps to upgrade to a new kernel using an existing configuration.
Removal
Steps to completely remove old kernels.
Kernel Seeds
Like the option above, Kernels Seeds help the user, with some effort, create a custom-fit kernel configuration using an existing .config as a base.
2.4 to 2.6 Migration
Migration guide from Linux 2.4 to Linux 2.6. Since the kernel has significantly moved past 2.6, these migration steps are no longer relevant, but may be useful for helping administrators understand.

See also

External resources