A Linux distribution is developed and distributed by developer groups, companies or private organizations. The Linux distributors take care of patching and upgrading the software and add their own program code. The most widely used Linux distributions include Ubuntu, Debian, openSUSE, Knoppix and Fedora.
Linux distributions are mainly available as downloads, many of them free of charge, or on optical media and USB sticks. The distributor finances itself through paid technical support and donations or volunteer work. The first paid Linux distribution was Yggdrasil Linux by Adam J. Richters in 1992 on a compact disc( CD).
A Linux distribution consists of a Linux kernel and GNU software with the base system and utilities called daemon processes. Much of the software comes from the GNU project( GNU is not Unix). Besides the kernel, additional software is needed for operational systems, e.g. the software of the GNU project.
Linux distributions can be run on common computer hardware for Windows and Mac OS X alongside the original operating system. They differ in the amount of additional software, the tools for installation, partitioning, configuration as well as the documentation. Many Linux distributions are not or only partially compatible with other distributions due to proprietary binary packages.
Individual Linux distributions are also suitable as firmware for technical products such as digital cameras or measuring devices. Insmartphones, Linux software controls features for telephony, communication, multimedia and personal organization. Linux systems for smartphones include the Android, Bada, Maemo or WebOS operating systems. They compete with AppleiOS, Microsoft Windows Phone and Blackberry OS.