Debian (pronounced [ˈdɛbiɛn]) is a computer operating system composed entirely of free software. Its primary form, Debian GNU/Linux, is a popular and influential Linux distribution.
Debian is known for its adherence to the Unix and free software philosophies, and for its abundance of options — the current release includes over eighteen thousand software packages for eleven computer architectures, ranging from the ARM architecture commonly found in embedded systems and the IBM eServer zSeries mainframe architecture to the more common Intel x86 architecture found in modern personal computers. Debian GNU/Linux is the basis for several other distributions, including Knoppix, Linspire, MEPIS, Xandros, and the Ubuntu family.
Debian is also known for its package management system (especially APT), for its strict policies regarding its packages and the quality of its releases. These practices afford easy upgrades between releases and easy automated installation and removal of packages.
Debian uses an open development and testing process. It is developed by volunteers from around the world and supported by donations through Software in the Public Interest, Inc., a non-profit umbrella organization for free software projects.
Advantages and criticisms
The Debian system provides over 18200 precompiled packages. The stable release goes through a rigorous release cycle, so the system and packages are stable. But the rigorous release cycles can take time, so a technical criticism of Debian is that the released stable branch can become too old for users' tastes. Almost three years elapsed between Debian 3.0 and Debian 3.1, and Debian 4.0 was announced for December 2006 (18 months after the release of 3.1) but released on April 8, 2007.
Repositories of backported packages contain updated package versions compiled in the stable environment. Examples are backports.org and apt-get.org. Their use requires precise configuration of the priority of the packages repositories to be merged, done in the /etc/apt/preferences file. Otherwise these packages may be less integrated into the system, and may cause problems upgrading or conflicts between backported packages from different sources. The testing branch of Debian is much more stable than its name might indicate. It receives frequent package updates, without most of the drawbacks of using the unstable branch.
Thus the stable branch together with the backports.org repository is most suitable for users and servers which need stability but not the latest versions of software.
Another criticism is that not all software and documentation is available in the official Debian software repository because it does not satisfy the Debian Project's requirements of freedom. Conversely, some in the free software community have criticized the Debian Project for making the non-free section available, rather than excluding proprietary software entirely. Also, Debian has in the past included proprietary device driver code (firmware) in its Linux kernel packages due to disagreement about whether Debian software guidelines extended to firmware for hardware components.