Ubuntu four Components

http://www.ubuntu.com/community/ubuntustory/components

Components

The Ubuntu software repository is divided into four components -main, restricted, universe and multiverse - on the basis of our abilityto support that software, and whether or not it meets the goals laidout in our Free Software Philosophy.

The standard Ubuntu installation is a subset of software availablefrom the main and restricted components. You can install additionalsoftware using installation software such as Synaptic Package Manageror Aptitude. Other components are added by editing the/etc/apt/sources.list file. See "man sources.list" for more informationon editing the sources.list file.

"main" component

The main distribution component contains applications that are freesoftware, can freely be redistributed and are fully supported by theUbuntu team. This includes the most popular and most reliable opensource applications available, much of which is installed by defaultwhen you install Ubuntu.

Software in main includes a hand-selected list of applications thatthe Ubuntu developers, community, and users feel are important and thatthe Ubuntu security and distribution team are willing to support. Whenyou install software from the main component you are assured that thesoftware will come with security updates and technical support.

We believe that the software in main includes everything most peoplewill need for a fully functional desktop or internet server runningonly open source software.

The licences for software applications in main must be free, butmain may also may contain binary firmware and selected fonts thatcannot be modified without permission from their authors. In all casesredistribution is unencumbered.

"restricted" component

The restricted component is reserved for software that is verycommonly used, and which is supported by the Ubuntu team even though itis not available under a completely free licence. Please note that itmay not be possible to provide complete support for this software sincewe are unable to fix the software ourselves, but can only forwardproblem reports to the actual authors.

Some software from restricted will be installed on Ubuntu CDs but isclearly separated to ensure that it is easy to remove. We include thissoftware because it is essential in order for Ubuntu to run on certainmachines - typical examples are the binary drivers that some video cardvendors publish, which are the only way for Ubuntu to run on thosemachines. By default, we will only use open source software unlessthere is simply no other way to install Ubuntu. The Ubuntu team workswith such vendors to accelerate the open-sourcing of their software toensure that as much software as possible is available under a Freelicence.

"universe" component

The universe component is a snapshot of the free, open source, andLinux world. In universe you can find almost every piece of open sourcesoftware, and software available under a variety of less open licences,all built automatically from a variety of public sources. The basictoolchain and system libraries from main are still used to build thissoftware and it is normally maintained in step with them, so it shouldinstall and work well with the software in main, but it comes with no guarantee of security fixes and support.The universe component includes thousands of pieces of software.Through universe, users are able to have the diversity and flexibilityoffered by the vast open source world on top of a stable Ubuntu core.

Canonical does not provide a guarantee of regular security updatesfor software found in universe but will provide these where they aremade available by the community. Users should understand the riskinherent in using packages from the universe component.

Popular or well supported pieces of software will move from universeinto main if they are backed by maintainers willing to meet thestandards set for main by the Ubuntu team.

"multiverse" component

The "multiverse" component contains software that is "not free",which means the licensing requirements of this software do not meet theUbuntu "main" Component Licence Policy.

The onus is on you to verify your rights to use this software and comply with the licensing terms of the copyright holder.

This software is not supported and usually cannot be fixed or updated. Use it at your own risk.

 

 

简单来说就是从上到下的支持越来越差。