Chapter 2

Using RPM to
Install Packages

Table 2.1. Install-mode command syntax and options.

2.1. rpm -i—What Does It Do?

Of the many things RPM can do, probably the one that users think of first, is the installation of software. As mentioned earlier, installing new software is a complex, error-prone job. RPM turns that process into a single command.

rpm -i (--install is equivalent) installs software that's been packaged into an RPM package file. It does this through the following process:

• Performs dependency checks. Some packages will not operate properly unless some other package is installed, too. RPM makes sure the package being installed will have its dependency requirements met. It also ensures that the package's installation will not cause dependency problems for other already-installed packages.
• Checks for conflicts. RPM performs a number of checks during this phase. These checks look for things such as attempts to install an already-installed package, attempts to install an older package over a newer version, or the possibility that a file might be overwritten.
• Performs any tasks required before the install. There are cases where one or more commands must be given prior to the actual installation of a package. RPM performs these commands exactly as directed by the package builder, thus eliminating a common source of problems during installations.
• Decides what to do with config files. One of the features that really sets RPM apart from other package managers is the way it handles configuration files. Since these files are normally changed to customize the behavior of installed software, simply overwriting a config file would tend to make people angry—all their customizations would be gone! Instead, RPM analyzes the situation and attempts to do "the right thing" with config files, even if they weren't originally installed by RPM!

• Unpacks files from the package and puts them in the proper place. This is the step most people think of when they think about installing software. Each package file contains a list of files that are to be installed, as well as their destination on your system. In addition, many other file attributes, such as permissions and ownerships, are set correctly by RPM.
• Performs any tasks required after the install. Very often a new package requires that one or more commands be executed after the new files are in place. An example of this is running ldconfig to make new shared libraries accessible.
• Keeps track of what has been done. Every time RPM installs a package on your system, it uses its database to keep track of the files it installed. The database contains a wealth of information necessary for RPM to do its job. For example, RPM uses the database when it checks for possible conflicts during an install.

2.2. Performing an Install

Let's have RPM install a package. The only thing necessary is to give the command rpm -i, followed by the name of the package file:

# rpm -i eject-1.2-2.i386.rpm

#

At this point, all the steps outlined previously have been performed. The package is now installed. Note that the filename need not adhere to RPM's file-naming convention:

# mv eject-1.2-2.i386.rpm baz.txt

# rpm -i baz.txt

#

In this case, we changed the name of the package file eject-1.2-2.i386.rpm to baz.txt and then proceeded to install the package. The result is identical to the previous install; that is, the eject-1.2-2 package successfully installed. The name of the package file, although normally incorporating the package label, is not used by RPM during the installation process. RPM uses the contents of the package file, which means that even if the file were placed on a DOS floppy and the name truncated, the installation would still proceed normally.

2.2.1. URLs: Another Way to Specify Package Files

If you've surfed the World Wide Web, you've no doubt noticed the way Web pages are identified. Here's an example:

http://www.redhat.com/support/docs/rpm/RPM-HOWTO/RPM-HOWTO.html

This is called a uniform resource locator, or URL. RPM can also use URLs, although they look a little bit different. Here's one:

ftp://ftp.redhat.com/pub/redhat/code/rpm/rpm-2.3-1.i386.rpm

ftp: signifies that this URL is a File Transfer Protocol URL. As the name implies, this type of URL is used to move files around. The section containing ftp.redhat.com specifies the hostname, or the name of the system where the package file resides.

The remainder of the URL (/pub/redhat/code/rpm/rpm-2.3-1.i386.rpm) specifies the path to the package file, followed by the package file itself.

RPM's use of URLs gives you the ability to install a package located on the other side of the world, with a single command:

# rpm -i ftp://ftp.gnomovision.com/pub/rpms/foobar-1.0-1.i386.rpm

#

This command would use anonymous FTP to obtain the foobar version 1.0 package file and install it on your system. Of course, anonymous FTP (no username and password required) is