README.md
1. addons : Contains packages required in order to build the main
Distribution or packages produced by SRPMS built in the main
Distribution, but not included in the main Redhat package tree (mysql-
server in CentOS-3.x falls into this category). Packages contained in
the addons repository should be considered essentially a part of the
core distribution, but may not be in the main Redhat Package tree.

2. apt : Contains all the apt RPMS for the CentOS site. This is where
you would point if you want to use apt to do updates. Apt has issues
with distros that use multiple libraries, so is only available for
the i386 distro.

3. centosplus : Packages contributed by CentOS Developers and the Users.
These packages might replace rpm's included in the core Distribution.
You should understand the implications of enabling and using packages
from this repository.

4. contrib : Packages contributed by the CentOS Users, which do not
overlap with any of the core Distribution packages. These packages have
not been tested by the CentOS developers, and may not track upstream
version releases very closely.

5. docs : Contains manuals and release notes for CentOS

6. extras : Packages built and maintained by the CentOS developers, that
add functionality to the core distribution. These packages have
undergone some basic testing, should track upstream release versions
fairly closely and will never replace any core distribution package.

7. isos : Contains the ISOs for download. On the main CentOS mirror sites
ISOs can not be downloaded directly, but we provide a Bittorent file for
downloading. On external public mirrors, ISOs may be downloadable directly.

8. os : Contains the base OS files that are on the Main ISO files.

9. updates : Contains updates released for the CentOS distro.

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We welcome contributions into the Contrib and CentOSPlus repository.
Post a message on the CentOS-Devel mailing list with details of packages
you would like to contribute, one of the CentOS developers will then
pick it up and work with you on the issue.

You might want to make sure that the same package is not already easily
available from some other mainstream repository. And, you should be
willing to maintain the packages in sync with upstream releases and fix's.