Appendix B. RPM
Appendix B. RPM The RPM Package Manager (RPM) is an open packaging system, which runs on Red Hat Enterprise Linux as well as other Linux and UNIX systems. Red Hat, Inc. and the Fedora Project encourage other vendors to use RPM for their own products. RPM is distributed under the terms of the GPL ( GNU General Public License ). The RPM Package Manager only works with packages built to work with the RPM format . RPM is itself provided as a pre-installed rpm package. For the end user, RPM makes system updates easy. Installing, uninstalling and upgrading RPM packages can be accomplished with short commands. RPM maintains a database of installed packages and their files, so you can invoke powerful queries and verifications on your system. The RPM package format has been improved for Red Hat Enterprise Linux 6. RPM packages are now compressed using the XZ lossless data compression format, which has the benefit of greater compression and less CPU usage during decompression, and support multiple strong hash algorithms, such as SHA-256, for package signing and verification. Warning For most package management tasks, the Yum package manager offers equal and often greater capabilities and utility than RPM. Yum also performs and tracks complicated system dependency resolution, and will complain and force system integrity checks if you use RPM as well to install and remove packages. For these reasons, it is highly recommended that you use Yum instead of RPM whenever possible to perform package management tasks. See Chapter 8, Yum . If you prefer a graphical interface, you can use the PackageKit GUI application, which uses Yum as its back end, to manage your system's packages. See Chapter 9, PackageKit for details. Important When installing a package, ensure it is compatible with your operating system and processor architecture. This can usually be determined by checking the package name. Many of the following examples show RPM packages compiled for the AMD64/Intel 64 computer architectures; thus, the RPM file name ends in x86_64.rpm . During upgrades, RPM handles configuration files carefully, so that you never lose your customizations-something that you cannot accomplish with regular .tar.gz files. For the developer, RPM allows you to take software source code and package it into source and binary packages for end users. This process is quite simple and is driven from a single file and optional patches that you create. This clear delineation between pristine sources and your patches along with build instructions eases the maintenance of the package as new versions of the software are released. Note Because RPM makes changes to your system, you must be logged in as root to install, remove, or upgrade an RPM package. B.1. RPM Design Goals To understand how to use RPM, it can be helpful to understand the design goals of RPM: Upgradability With RPM, you can upgrade individual components of your system without completely reinstalling. When you get a new release of an operating system based on RPM, such as Red Hat Enterprise Linux, you do not need to reinstall a fresh copy of the operating system your machine (as you might need to with operating systems based on other packaging systems). RPM allows intelligent, fully-automated, in-place upgrades of your system. In addition, configuration files in packages are preserved across upgrades, so you do not lose your customizations. There are no special upgrade files needed to upgrade a package because the same RPM file is used to both install and upgrade the package on your system. Powerful Querying RPM is designed to provide powerful querying options. You can perform searches on your entire database for packages or even just certain files. You can also easily find out what package a file belongs to and from where the package came. The files an RPM package contains are in a compressed archive, with a custom binary header containing useful information about the package and its contents, allowing you to query individual packages quickly and easily. System Verification Another powerful RPM feature is the ability to verify packages. If you are worried that you deleted an important file for some package, you can verify the package. You are then notified of anomalies, if any-at which point you can reinstall the package, if necessary. Any configuration files that you modified are preserved during reinstallation. Pristine Sources A crucial design goal was to allow the use of pristine software sources, as distributed by the original authors of the software. With RPM, you have the pristine sources along with any patches that were used, plus complete build instructions. This is an important advantage for several reasons. For instance, if a new version of a program is released, you do not necessarily have to start from scratch to get it to compile. You can look at the patch to see what you might need to do. All the compiled-in defaults, and all of the changes that were made to get the software to build properly, are easily visible using this technique. The goal of keeping sources pristine may seem important only for developers, but it results in higher quality software for end users, too.