If you chose to upgrade your system from a previous release rather than perform a fresh installation, you may want to examine the differences in the package set. Section 9.11.2, “ Upgrading Using the Installer ”, Section 16.13.2, “ Upgrading Using the Installer ”, or Section 23.12.1, “ Upgrading Using the Installer ” (depending on your system architecture) advised you to create a package listing for your original system. You can now use that listing to determine how to bring your new system close to the original system state.

Most software repository configurations are stored in packages that end with the term release. Check the old package list for the repositories that were installed:

awk '{print $1}' ~/old-pkglist.txt | grep 'release$'

If necessary, retrieve and install these packages from their original sources on the Internet. Follow the instructions at the originating site to install the repository configuration packages for use by yum and other software management tools on your Red Hat Enterprise Linux system.

Then run the following commands to make a list of other missing software packages:

awk '{print $1}' ~/old-pkglist.txt | sort | uniq > ~/old-pkgnames.txt
rpm -qa --qf '%{NAME}\n' | sort | uniq > ~/new-pkgnames.txt
diff -u ~/old-pkgnames.txt ~/new-pkgnames.txt | grep '^-' | sed 's/^-//' > /tmp/pkgs-to-install.txt

Now use the file /tmp/pkgs-to-install.txt with the yum command to restore most or all of your old software:

su -c 'yum install `cat /tmp/pkgs-to-install.txt`'