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Debian

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The Debian logo is a red swirl
The Debian logo is a red swirl

Debian, created by the Debian Project, is a widely used distribution of free software developed through the collaboration of volunteers from around the world. Since its inception, the released system, Debian GNU/Linux, has been based on the Linux kernel with many basic tools of the operating system from the GNU project.

Debian is known for its adherence to the Unix and free software philosophies, and its plethora of choice: the current release contains over eight and a half thousand software packages for eleven computer architectures, ranging from the ARM architecture commonly found in embedded systems and the IBM s390 mainframe architecture to the more common x86 and PowerPC architectures found in modern personal computers.

The Project describes itself as creating "The Universal Operating System" and develops ports to other kernels: Debian GNU/Hurd, Debian GNU/NetBSD and Debian GNU/FreeBSD. Those ports have yet to be officially released, so it is still accurate to describe Debian as a "GNU/Linux distribution".

Debian is also notable for its package management system, namely APT, the Advanced Packaging Tool, its strict policies regarding the quality of its packages and releases, and its open development and testing process. These practices afford easy upgrades between releases without rebooting and easy installation and removal of packages.

Debian is supported by donations through Software in the Public Interest (SPI Inc.), a non-profit umbrella organization for free software projects.

History

Debian was founded in 1993 by Ian Murdock, then a university student, who wrote the Debian Manifesto which called for the creation of a Linux distribution to be maintained in an open manner, in the spirit of Linux and GNU. He chose the name by combining the first name of his then-girlfriend (now wife) Debra with his own first name "Ian", forming the portmanteau "Debian", pronounced as the corresponding syllables of these names are in American English: /deb' ē ən/. The Debian Project grew slowly at first and released its first 0.9x versions in 1994 and 1995. The first ports to other architectures started being made 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. He initiated the creation of several important documents, like a social contract for the project and Debian Free Software Guidelines) and the legal umbrella organization (SPI). Bruce Perens left in 1998 before the release of the first glibc-based Debian, 2.0. The Project proceeded to elect new leaders and make two more 2.x releases, each including more ports and more packages. APT was deployed during this time and the Debian GNU/Hurd was started as well.

The year 1999 brought the first other Linux distributions based on Debian, Corel Linux and Stormix's Storm Linux, neither of which is developed any more but which started what is now a notable trend of basing distributions on Debian.

In late 2000, the project switched to the use of the package pools and began the "testing" distribution, marking a major change in archive and release management. In 2001, developers began holding an annual conference called Debconf with talks, workshops, and technical users welcome. The 3.0 release of 2002 included more than double the number of packages of the previous release and supported five new architectures. Debian celebrated its tenth anniversary on August 16, 2003, with parties held around the world.

See A Brief History of Debian for a more comprehensive history.

Debian releases

The latest released version of Debian is called stable. As of 2003, the stable release has version 3.0. In addition, a stable release gets minor updates (the so-called point releases) marked e.g. 3.0r1.

The code names of Debian releases are the names of characters from the movie Toy Story:

  • 3.1 -- sarge, anticipated in 2004 (tentative designation)
  • 3.0 -- woody, July 19th, 2002
  • 2.2 -- potato, August 15th, 2000
  • 2.1 -- slink, March 9th, 1999
  • 2.0 -- hamm, July 24th, 1998
  • 1.3 -- bo, June 2nd, 1997
  • 1.2 -- rex, 1996
  • 1.1 -- buzz, 1996

Because a CD vendor made an unofficial and broken release labelled "1.0", the Project skipped a "1.0" release in order to avoid confusion.

The release after 3.0 is codenamed sarge. The version number is yet to be determined, but will likely be 3.1. It is currently in a state called "testing", which is a staging area for the next release. The day-to-day development takes place in the "unstable" branch which is permanently codenamed sid[1], after the boy next door who broke toys.

Note that software in the "unstable" branch is not necessarily unstable, only that the packaging and other Debian-specific modifications may be new and untested. Software which is itself unstable is generally placed in "experimental".

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 so 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.
  • 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.

Together, the Developers may make binding general decisions by way of a General Resolution or election. All voting is conducted by the Condorcet method of ranked election with a version of Cloneproof Schwartz Sequential Dropping modified with approval voting. A Project Leader is elected once per year by a vote of the Developers. 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 delgegates, 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.

Perhaps a more important person to Debian than the Leader is the Release Manager, who sets goals for the next "stable" release, supervises the process, and makes 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.

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:

  • 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 (some developers have a nearly obsessive level of dedication to refinement and enhancement of software).

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).

Debian package life cycle

Each Debian package has a maintainer (typically, only one, but occasionally small teams of developers supervise particularly complex pieces of software). It is the maintainer's responsibility to keep pace with the releases of officially-authored versions of the software (called "upstream"), if any exist, to ensure that the package is compliant with Debian Policy thereby making it work on all machine architectures Debian supports (making it portable), easier to use, more configurable, more secure, and so forth, and finally to field any bug reports in the package reported by its users (who may include other Debian developers).

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 the upload is well-formed (all the requisite files are in place) and that the package bears the digital signature -- produced with OpenPGP-compatible software -- of a Debian developer. 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:

  • 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 architectures slated to release;
  • 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")
  • must not depend on versions of any packages which 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.

Footnotes

[1] Some refer to sid as an acronym for Still In Development, but this is an unofficial back-formation that is not often used.

Distributions based on Debian

Many distributions are based on Debian; examples include:

See more complete listings at Debian's web pages and DistroWatch.

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