15.2.4. Upgrading

Upgrading a package is similar to installing one. Type the following command at a shell prompt: 
rpm -Uvh foo-2.0-1.i386.rpm
As part of upgrading a package, RPM automatically uninstalls any old versions of the foo package. In fact, you may want to always use -U to install packages which works even when there are no previous versions of the package installed.

Note

You don't want to use the -U option for installing kernel packages because RPM replaces the previous kernel package. This does not affect a running system, but if the new kernel is unable to boot during your next restart, there would be no other kernel to boot instead.
Using the -i option adds the kernel to your GRUB boot menu (/etc/grub.conf). Similarly, removing an old, unneeded kernel removes the kernel from GRUB.
Because RPM performs intelligent upgrading of packages with configuration files, you may see a message like the following: 
saving /etc/foo.conf as /etc/foo.conf.rpmsave
This message means that your changes to the configuration file may not be forward compatible with the new configuration file in the package, so RPM saved your original file and installed a new one. You should investigate the differences between the two configuration files and resolve them as soon as possible, to ensure that your system continues to function properly.
Upgrading is really a combination of uninstalling and installing, so during an RPM upgrade you can encounter uninstalling and installing errors, plus one more. If RPM thinks you are trying to upgrade to a package with an older version number, the output is similar to the following: 
package foo-2.0-1 (which is newer than foo-1.0-1) is already installed
To force RPM to upgrade anyway, use the --oldpackage option: 
rpm -Uvh --oldpackage foo-1.0-1.i386.rpm