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Unix in a Nutshell, 4th Edition by Arnold Robbins

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Yum: Yellowdog Updater Modified

Yum is a system for managing RPM packages, including installing, updating, removing, and maintaining packages; it automatically handles dependencies between packages. Yum is derived from yup, an updating system written for Yellow Dog Linux, an RPM-based Macintosh distribution. Yum downloads the information in the package headers to a directory on your system, which it then uses to make decisions about what it needs to do. Yum obtains both the headers and the RPMs themselves from a collection of packages on a server, known as a repository.

A repository consists of a set of RPM packages and the package headers on a server that can be accessed via FTP or HTTP, from an NFS server, or from a local filesystem. A single server can contain multiple repositories, repositories are often mirrored on many servers, and you can configure yum to use multiple repositories. When they are downloaded to your system, the header and package files are maintained in /var/cache/yum.

The configuration file, /etc/yum.conf, is where you customize yum. It consists of two section types. The first section, [main], sets configuration defaults for yum operation. This section is followed by [ server ] sections, where each server is named according to the repository it specifies. For example, for Fedora Core, you might have [base] for the base Fedora Core repository and [development] for the development repository.

The server sections can also be stored, one to a file, in /etc/yum.repos.d ...

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