Debian

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Debian GNU/Linux
Debian Etch's default GNOME desktop
Website	http://www.debian.org
Company/ developer	Debian Project
OS family	GNU/Linux
Source model	Free and open source software
Initial release	August 16, 1993 (1993-08-16) (age 14)
Latest stable release	4.0r3 Etch / February 17, 2008 (2008-02-17), 10 days ago
Available language(s)	Multilingual
Update method	APT
Package manager	dpkg
Supported platforms	x86-32, x86-64, PowerPC, SPARC, DEC Alpha, ARM, MIPS, HPPA, S390, IA-64
Kernel type	Monolithic (Linux)
Default user interface	GNOME, KDE & Xfce (see freedesktop.org)
Working state	Current

Debian (pronounced [ˈdɛbiən]) is a computer operating system composed entirely of software which is both free and open source. Its primary form, Debian GNU/Linux, is a popular and influential Linux distribution.^[1]

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. These architectures range from the common Intel/AMD 32-bit/64-bit architectures found in personal computers to the ARM architecture commonly found in embedded systems and the IBM eServer zSeries mainframes. Throughout Debian's lifetime, many other distributions have taken it as a basis to develop their own, some include: Ubuntu, MEPIS, Dreamlinux, Damn Small Linux, Xandros, Knoppix, Linspire, sidux, Kanotix, and LinEx among many others. A university's study stated that Debian's 283 million source code lines would cost 10 billion USD to develop by conventional means.^[2]

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 SPI, Inc., a non-profit umbrella organization for free software projects.

Debian's default install is very complete, providing the user with popular programs such as: OpenOffice, Iceweasel browser, Evolution mail, CD/DVD writing programs, music/video players, image viewers/editors, PDF viewers and many others. Only the first CD/DVD is necessary for the default install; the remaining discs contain all 18,000+ extra programs and packages currently available. If a user does not wish to download the CDs/DVDs, these extras can be downloaded separately using the package manager. Debian can also be configured to download and install updates automatically.

Contents 1 History 2 Development procedures 3 Project organization 4 Developer recruitment, motivation, and resignation 5 Package life cycle 6 Releases 7 Ports 7.1 Architectures 7.2 Kernels 7.3 Desktop environments 7.4 Debian Live 8 Volatile updates, backports & Debian Testing 9 See also 10 Notes 11 References 12 External links

[edit] History

Debian was first announced on 16 August 1993 by Ian Murdock, then a student at Purdue University. Murdock initially called his system the "Debian Linux Release".^[3] Previously, Softlanding Linux System had been the first well-known attempt at making a Linux distribution from various software packages, and was a popular option among Linux users in 1994.^[4] It was the perceived poor maintenance and prevalence of bugs in SLS^[5] that motivated Murdock to launch a new distribution.

In the Debian Manifesto, Murdock called for the creation of a distribution to be maintained in an open manner, in the spirit of Linux and GNU. He formed the name "Debian" as a portmanteau of the first name of his girlfriend (now wife) Debra and his own first name. As such, Debian is pronounced as the corresponding syllables of these names in American English: /'dɛbiən/^[6] but other pronunciations are common in different parts of the world.^[7]

The Debian Project grew slowly at first and released its first 0.9x versions in 1994 and 1995. The first ports to other architectures were begun in 1995, and the first 1.x version of Debian was released in 1996. In 1996, Bruce Perens replaced Ian Murdock as the project leader. In the same year, fellow developer Ean Schuessler suggested that Debian establish a social contract with its users. He distilled the resulting discussion on Debian mailing lists into the Debian Social Contract and the Debian Free Software Guidelines, defining fundamental commitments for the development of the distribution. He also initiated the creation of the legal umbrella organization Software in the Public Interest.

Perens left in 1998 before the release of the first glibc-based Debian, 2.0. The Project elected new leaders and made two more 2.x releases, each including more ports and packages. The Advanced Packaging Tool was deployed during this time and the first port to a non-Linux kernel, Debian GNU/Hurd, was started. The first Linux distributions based on Debian, Libranet, Corel Linux and Stormix's Storm Linux, were started in 1999. Though no longer developed, these distributions were the first of many distributions based on Debian.

In late 2000, the project made major changes to archive and release management, reorganizing software archive processes with new "package pools" and creating a testing branch as an ongoing, relatively stable staging area for the next release. Also in that year, developers began holding an annual conference called DebConf with talks and workshops for developers and technical users.^[8]

On April 8, 2007 the project announced the official release of Debian GNU/Linux version 4.0, codenamed "Etch".

[edit] Development procedures

Software packages in development are either uploaded to the project branch named unstable, also known as sid, or the experimental branch. Software packages uploaded to unstable are normally versions stable enough to be released by the original upstream developer, but with the added Debian-specific packaging and other modifications introduced by Debian developers. These additions may be new and untested. Software not ready yet for the unstable branch is typically placed in the experimental branch.

After a version of a software package has remained in unstable for a certain length of time (depending on the urgency of the software's changes), that package is automatically migrated to the testing branch. The package's migration to testing occurs only if no serious (release-critical) bugs in the package are reported and if other software needed for package functionality qualifies for inclusion in testing.

Since updates to Debian software packages between official releases do not contain new features, some choose to use the testing and unstable branches for their newer packages. However, these branches are less tested than stable, and unstable doesn't receive timely security updates.^[9] Starting September 9, 2005^[10] a testing security team provides security updates.^[11] In particular, incautious upgrades to working unstable packages can sometimes seriously break software functionality.

After the packages in testing have matured and the goals for the next release are met, the testing branch becomes the next stable release. The latest stable release of Debian (etch) is 4.0. It was released on April 8, 2007.

The forthcoming version is codenamed "lenny."

[edit] Project organization

The Debian Project is a volunteer organization with three foundational documents:

• The Debian Social Contract defines a set of basic principles by which the project and its developers conduct affairs.
• The Debian Free Software Guidelines define the criteria for "free software" and thus what software is permissible in the distribution, as referenced in the Social Contract. These guidelines have also been adopted as the basis of the Open Source Definition. Although it can be considered a separate document for all practical purposes, it formally is part of the Social Contract.
• The Debian Constitution describes the organizational structure for formal decision-making within the Project, and enumerates the powers and responsibilities of the Debian Project Leader, the Debian Project Secretary, and the Debian Developers generally.

Currently, the project includes more than a thousand developers. Each of them sustains some niche in the project, be it package maintenance, software documentation, maintaining the project infrastructure, quality assurance, or release coordination. Package maintainers have jurisdiction over their own packages, although packages are increasingly co-maintained. Other tasks are usually the domain of smaller, more collaborative groups of developers.

The project maintains official mailing lists and conferences for communication and coordination between developers. For issues with single packages or domains, a public bug tracking system is used by developers and end-users both. Informally, Internet Relay Chat channels (primarily on the OFTC and freenode networks) are used for communication among developers and users as well.

Together, the Developers may make binding general decisions by way of a General Resolution or election. All voting is conducted by Cloneproof Schwartz Sequential Dropping, a Condorcet method of voting. A Project Leader is elected once per year by a vote of the Developers; in April 2007, Sam Hocevar was voted into this position, succeeding Anthony Towns. The Debian Project Leader has several special powers, but this power is far from absolute and is rarely utilized. Under a General Resolution, the Developers may, among other things, recall the leader, reverse a decision by him or his delegates, and amend the constitution and other foundational documents.

The Leader sometimes delegates authority to other developers in order for them to perform specialized tasks. Generally this means that a leader delegates someone to start a new group for a new task, and gradually a team gets formed that carries on doing the work and regularly expands or reduces their ranks as they think is best and as the circumstances allow.

A role in Debian with a similar importance to the Project Leader's is Release Manager. Release Managers set goals for the next release, supervise the process, and make the final decision as to when to release.

A list of many important positions in the Debian project is available at the Debian organization web page.

[edit] Developer recruitment, motivation, and resignation

The Debian project has a steady influx of applicants wishing to become developers. These applicants must undergo an elaborate vetting process which establishes their identity, motivation, understanding of the project's goals (embodied in the Social Contract), and technical competence. More information on the "New Maintainer" process is available at the Debian New Maintainer page.

Debian Developers join the Project for any number of reasons; some that have been cited in the past include^{[citation needed]}:

• a desire to contribute back to the Free Software community (practically all applicants are users of Free Software);
• a desire to see some specific software task accomplished (some view the Debian user community as a valuable testing or proving ground for new software);
• a desire to make, or keep, Free Software competitive with proprietary alternatives;
• a desire to work closely with people that share some of their aptitudes, interests, and goals (there is a very strong sense of community within the Debian project which some applicants do not experience in their paid jobs);
• a simple enjoyment of the iterative process of software development and maintenance.

Debian Developers may resign their positions at any time by orphaning the packages they were responsible for and sending a notice to the developers and the keyring maintainer (so that their upload authorization can be revoked).

[edit] Package life cycle

Each Debian software package has a maintainer who keeps track of releases by the "upstream" authors of the software and ensures that the package is compliant with Debian Policy, coheres with the rest of the distribution, and meets the standards of quality of Debian. In relations with users and other developers, the maintainer uses the bug tracking system to follow up on bug reports and fix bugs. Typically, there is only one maintainer for a single package, but increasingly small teams of developers "co-maintain" larger and more complex packages and groups of packages.

Periodically, a package maintainer makes a release of a package by uploading it to the "incoming" directory of the Debian package archive (or an "upload queue" which periodically batch-transmits packages to the incoming directory). Package uploads are automatically processed to ensure that they are well-formed (all the requisite files are in place) and that the package is digitally signed by a Debian developer using OpenPGP-compatible software. All Debian developers have public keys. Packages are signed to be able to reject uploads from hostile outsiders to the project, and to permit accountability in the event that a package contains a serious bug, a violation of policy, or malicious code.

If the package in incoming is found to be validly signed and well-formed, it is installed into the archive into an area called the "pool" and distributed every day to hundreds of mirrors worldwide. Initially, all package uploads accepted into the archive are only available in the "unstable" suite of packages, which contains the most up-to-date version of each package.

However, new code is also untried code, and those packages are only distributed with clear disclaimers. For packages to become candidates for the next "stable" release of the Debian distribution, they first need to be included in the "testing" suite. The requirements for a package to be included in "testing" is that it:^[12]

• must have been in unstable for the appropriate length of time (the exact duration depends on the "urgency" of the upload).
• must not have a greater number of "release-critical" bugs filed against it than the current version in testing. Release-critical bugs are those bugs which are considered serious enough that they make the package unsuitable for release.
• must be compiled for all release architectures the package claims to support (eg: the i386-specific package gmod can be included in "testing").
• must be a package for an architecture that is slated to release (in other words, packages for architectures that aren't scheduled to release with all the rest are never considered for "testing").^[13]
• must not depend on versions of any packages that do not meet the above conditions.

Thus, a release-critical bug in a package on which many packages depend, such as a shared library, may prevent many packages from entering the "testing" area, because that library is considered deficient.

Periodically, the Release Manager publishes guidelines to the developers in order to ready the release, and in accordance with them eventually decides to make a release. This occurs when all important software is reasonably up-to-date in the release-candidate suite for all architectures for which a release is planned, and when any other goals set by the Release Manager have been met. At that time, all packages in the release-candidate suite ("testing") become part of the released suite ("stable").

It is possible for a package -- particularly an old, stable, and seldom-updated one -- to belong to more than one suite at the same time. The suites are simply collections of pointers into the package "pool" mentioned above.

[edit] Releases

As of April 2007, the latest stable release is version 4.0, code name etch.^[14] When a new version is released, the previous stable is labeled oldstable; currently, this is version 3.1, code name sarge.

In addition, a stable release gets minor updates (called point releases) marked, for example, like 4.0r3.

The Debian security team releases security updates for the latest stable major release, as well as for the previous stable release for one year.^[15] As version 4.0 Etch was released on 8 April 2007, this means that the security team expects to support version 3.1 Sarge until April 2008. For most uses it is strongly recommended to run a system which receives security updates. The testing version also receives security updates.^[16]

Debian has made nine major stable releases:^[17]

Color	Meaning
Red	Old release; not supported
Yellow	Old release; still supported
Green	Current release
Blue	Future release

Version	Code name	Release date	Archs	Packages	Support	Notes
1.1	buzz	17 June 1996	1	474	1996	dpkg, ELF transition, Linux 2.0[18]
1.2	rex	12 December 1996	1	848	1996	-
1.3	bo	5 June 1997	1	974	1997	-
2.0	hamm	24 July 1998	2	~ 1500	1998	glibc transition, new architecture: m68k[19]
2.1	slink	9 March 1999	4	~ 2250	2000-12	APT, new architectures: alpha, sparc[20]
2.2	potato	15 August 2000	6	~ 3900	2003-04	New architectures: arm, powerpc[21]
3.0	woody	19 July 2002	11	~ 8500	2006-08	New architectures: hppa, ia64, mips, mipsel, s390[22]
3.1	sarge	6 June 2005	11	~ 15400	2008-04.[15]	Modular installer, semi-official amd64 support
4.0	etch	8 April 2007	11	~ 18000	2009-09.[15]	Graphical installer, udev transition, modular X.Org transition, new architecture: amd64, dropped architecture: m68k[23]
TBA	lenny[24]	Planned for September 2008[25]	TBA	TBA	TBA[15]	32-bit SPARC architecture dropped. New Debian GNU/kFreeBSD port. Almost complete UTF-8 support.[25]

Due to an incident involving a CD vendor who made an unofficial and broken release labeled 1.0, an official 1.0 release was never made.^[26]

The code names of Debian releases are names of characters from the film Toy Story. The unstable, development distribution is nicknamed sid, after the emotionally unstable next-door neighbour boy who regularly destroyed toys.^[27]

[edit] Ports

[edit] Architectures

As of the current stable release, the official ports are:^[28]

• i386 – x86-32 architecture designed for Intel/AMD 32-bit PCs and various other systems
• amd64 – x86-64 architecture designed for Intel/AMD 64-bit PCs and various other systems
• alpha – DEC Alpha architecture
• sparc – Sun SPARC architecture on Sun-4m, Sun-4u, and Sun-4v systems
• arm – ARM architecture on Risc PC and various embedded systems (little-endian)
• powerpc – PowerPC architecture
• hppa – HP PA-RISC architecture
• ia64 – Intel Itanium (IA-64) architecture
• mips, mipsel – MIPS architecture (big-endian and little-endian)
• s390 – IBM ESA/390 architecture and z/Architecture

The m68k port was the second official port in Debian, and has been part of five stable Debian releases. Due to its failure to meet the release criteria, it has been dropped before the release of etch. Still, it continues to be available as part of the unstable distribution:

• m68k – Motorola 68k architecture on Amiga, Atari, Macintosh, and various embedded VME systems

Ongoing efforts include ports to Hitachi SuperH and Renesas M32R architectures, big-endian ARM port (armeb), little-endian EABI ARM port (armel), and 64-bit-only PowerPC port (ppc64).

[edit] Kernels

For more details on this topic, see GNU variants.

The Project describes itself as creating a "Universal Operating System" and several ports of all userland software to various operating system kernels are under development:^[29]

• Debian GNU/Linux, on the Linux kernel — the original, officially released port
• Debian GNU/Hurd, on GNU Hurd
• Debian GNU/kFreeBSD, on the FreeBSD kernel
• Debian GNU/NetBSD, on the NetBSD kernel

Although these are official Debian projects, there have been no official releases of the non-Linux ports yet, so currently Debian is exclusively a Linux distribution.

[edit] Desktop environments

Debian's current release offers three different official CD1s, one for each major desktop environment (freedesktop.org): GNOME, the default desktop environment, along with KDE and Xfce as alternatives.

[edit] Debian Live

One can create a Debian LiveCD and LiveUSB. ^[30]

[edit] Volatile updates, backports & Debian Testing

The Debian Project has rigorous requirements for software to be considered free. This is why not all software and documentation is available in the official Debian software repository. For example, documents using the GNU Free Documentation License with sections that the author does not permit to be altered or removed are considered non-free by Debian.^[31] 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.

The stable release goes through a rigorous release cycle, so the system and packages are very stable. But the rigorous release cycles can take time, so a technical criticism of Debian is that the released stable branch can sometimes 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^[32] (18 months after the release of 3.1) but released on April 8, 2007.

These "criticisms" are countered to some degree by the existence of volatile updates, backports and Debian testing. The volatile project contains updates to the stable release for programs whose functionality requires frequent updates such as spam filtering programs.^[33] Repositories of backported packages contain updated package versions compiled in the stable environment such as 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. Testing is recommended for users who like to live "on the bleeding edge", with updates and corrections released very frequently (sometimes every week). The unstable branch is for Debian developers who participate in a project and need the latest libraries available. There is one distribution based on Debian unstable / sid called sidux.

[edit] See also

• Comparison of Linux distributions
• Debian repository
• DCC Alliance
• List of Debian-based Linux distributions
• List of Debian Project Leaders

[edit] Notes

[edit] References

[edit] External links

• Official website
• Debian GNU/Linux at DistroWatch
• Original comp.os.linux.development announcement from 1993

v • d • e Debian
Infrastructure	Debian Manifesto · DebConf · Software in the Public Interest · Debian Free Software Guidelines · Debian Social Contract · Alioth
Software	.deb format · dpkg · APT · aptitude · debconf package · Debian-Installer · Debian Iceweasel · Alien · Jigdo · dash
Derivatives	Debian GNU/Hurd · Custom Debian Distribution
People	Ian Murdock · Bruce Perens · List of Debian Project Leaders

v • d • e Linux distributions
CentOS · Debian · Fedora · Gentoo Linux · Knoppix · Mandriva Linux · openSUSE · Red Hat Enterprise Linux · Slackware · Ubuntu · more…