Kernel.org is a main repository

Repository (version control)

A Repository is a concept from distributed revision control that refers to a data structure, usually stored on a server, that contains, among other things:* A set of files and directories.* Historical record of changes in the repository....

 of source code for the Linux kernel

Linux kernel

The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....

, the base of the popular Linux

Linux

Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...

 operating system

Operating system

An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

. It makes all versions of the source code available to all users. It also hosts various other projects, like Google Android. The main purpose of the site is to host a repository for Linux kernel developers and maintainers of Linux distributions.

2011 attack

On 28 August 2011, developers at www.kernel.org realized that there had been a major security breach. Crackers had gained root access to the system and added a trojan to the startup scripts. Developers reinstalled all the servers and investigated the origin of the attack. It is likely, though not yet known, whether this is related to the LinuxFoundation.org

Linux Foundation

The Linux Foundation is a non-profit technology consortium chartered to foster the growth of Linux.Founded in 2007 by the merger of the Open Source Development Labs and the Free Standards Group , the Linux Foundation sponsors the work of Linux creator Linus Torvalds and is supported by leading...

 and Linux.com

Linux.com

Linux.com is the name of a website owned by the Linux Foundation. The site is currently a central source for Linux information, software, documentation and answers across the server, desktop/netbook, mobile, and embedded areas. Linux.com offers free Linux tutorials, news and blogs, discussion...

 website hacks found shortly afterwards.

Kernel.org is not the primary repository, but rather a distribution point of the kernel sources. Because the Linux kernel uses Git

Git (software)

Git is a distributed revision control system with an emphasis on speed. Git was initially designed and developed by Linus Torvalds for Linux kernel development. Every Git working directory is a full-fledged repository with complete history and full revision tracking capabilities, not dependent on...

, a distributed revision control

Distributed revision control

A distributed revision control system , distributed version control or decentralized version control keeps track of software revisions and allows many developers to work on a given project without necessarily being connected to a common network.-Distributed vs...

system designed to guarantee the integrity of the source code, any attack on the source code can be detected and reverted.

As of November 2011, kernel.org is completely back up.