Overview:
This article is visiting the forum is found, borrowed in order to learn.
The main source list /etc/apt/sources.list file
but also to create an independent source profile to the next /etc/apt/sources.list.d/*
sources.list file format specification
In units of the source file list, a plurality of sub-fields per row, separated by whitespace between fields. (#) At the beginning of the pound sign is comments.
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A first field indicating a packet type
Alternatively value [deb] [deb-src] two, corresponding to the binary packages and the package. Usually only useful for binary packages.
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A second field indicating the mirror site, i.e., the source URL
Positioning URL to a directory, the directory must [dists] [pool] two subdirectories.
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The third field indicating warehouse
Open a source, enter [dists] directory, inside each subdirectory can be understood as a warehouse.
Named in the form of "system release name - Warehouse names" such as Debian's [jessie-backports] [jessie- updates]. [stable, testing is a link to the specific system release, will change over time].
Debian squeeze the warehouse since Ubuntu is basically the same. In addition to the main storage, there are:
[Security], used to refer to the Ubuntu security updates. That is affecting the system security bug patches. Some special Debian, see below.
[updates], non-security updates. That does not affect system security bug patches.
[proposed-updates], pre-update. Small beta. After enter [updates] or [security]. Ubuntu only [proposed], without the suffix [updates].
[backports], reserve. After Debian stable release, a version of Ubuntu after the official release, all of which software version is already frozen, all just repair software bug, not add any properties. But some may need new features, and even some of the newer software had none at all. The warehouse being thus established, but due to the Crown to maintain, and may have some time after the system officially released content. This second sequence in the warehouse, and said first sequence number in the repository. Mounting a second priority packet must be specified, see apt-get (8) aptitude ( 8) of --target-release option.
Note: Not all versions are equipped with all of the above warehouses, open source dists catalog.
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Subsequent fields, the package license type indicates
Follow-up field in alphabetical order, the final result whichever union.
Per license package itself and depend directly pack license division. Open a warehouse, you can see several subdirectories.
Debian up to three
[main], the software itself is free, and all dependent packages are also free software, these can be called pure free software.
[contrib], the software itself is free, but relies impure, that is dependent on at least one case in non-free or contrib persons.
[non-free], itself is not free software, no matter how dependent.
Ubuntu up to four
[main], the official free software maintenance.
[universe], maintained by the Free Software community.
[restricted], device-specific driver.
[multiverse], with the Debian [non-free].
Some alternative third-party source, may not follow the above practices. In short, open the repository directory to look up.
Special
Debian 安全性更新不像 Ubuntu 放在[security]仓库，而是放在单独一个源中。各大镜像站通常都把一般的包放在根下来一级的[debian]目录中，而安全性更新则会放在[debian-security]目录中，如果有的话，如 http://ftp.cn.debian.org/debian-security/ 。
Debian 官方建议，所有安全性更新，只从官方主站更新，勿使用其它镜像站，除非你对镜像站非常有信心，见 https://www.debian.org/security/index.en.html 。所以，很多镜像站并不提供安全更新源。
安全性更新的第三字段形式固定为[版本名/updates]，如[wheezy/updates] [jessie/updates]。
Debian 多媒体源
一些多媒体软件因牵涉到版权问题，包括硬件解码器，Debian 官方并未收录，有一网站专门填补该空缺，见 http://www.deb-multimedia.org。
最后忠告
不要同时启用多个源，同一仓库的源启用一个即可，否则容易引起混乱。以下实例便是列有多套而仅启用一套.