Chapter 37. Advanced yum

IN THIS CHAPTER:

• Getting Started

• Running yum Noninteractively

• Using yum to Remove Packages

• Maintaining yum

• Using yum to Manage Package Inventory

• Configuring yum

• Creating a Local yum Repository

• Reference

Fedora is provided with a large amount of packages already supplied and ready to go. However, since Fedora Core 4, The Fedora Project has been on a mission to put Fedora on a massive "slim-fest," mainly because the distribution and the number of packages included were beginning to get out of control. Now, Fedora is released with a core of software that is designed to get you up and running in any one of many different configurations such as a web server, development environment, or a database server. Consequently you are stuck with this core of software when you first install. However, Fedora also comes with a great package management tool, called yum, which enables you to quickly and easily download and install packages. The yum tool (Yellowdog Updater, Modified) has been included with Fedora since version 1 and has become the tool of choice for installing and updating applications. In this chapter, we will take a look at how yum works, its basic usage, and more advanced package and repository management.

yum is controlled entirely from the command line, so you will have to memorize some useful switches to get the most from it. But before we go into yum itself, it is worthwhile understanding what goes on behind the scenes. How does yum actually work?

It is easiest to think of yum as a software layer that utilizes the rpm command. When you issue commands to yum, it automatically accesses various repositories and downloads the rpm headers that are then queried using the rpm command. The advantage to this is that all the processing takes place locally, without the need to download the entire RPM itself. Typically, the RPM header makes up a very small portion of the file, which makes it easy to handle and quick to download. yum builds and maintains a local cache of header files, attributed to the supplying repository, and queries this when you use yum. Each time yum is invoked, it checks the repositories for any updates. If any are found, it adds new headers to its cache, thereby making it as up-to-date as possible when you need to use it. Because yum uses rpm, there should be no dependency problems, making it a fast and easy way to install and update software.

yum is primarily controlled by its configuration file, yum.conf, and by the contents of the yum.repos.d directory, both of which can be found in /etc. By default, yum uses the Red Hat and Fedora repositories for updates, but you can easily add more of your own if you want to install other software that is not available from Red Hat.

Like apt, yum is incredibly easy to use, requiring a single command with a switch to update all the software in Fedora.