16.14.2.  Upgrading Using the Installer

Note

In general, Red Hat recommends that you keep user data on a separate /home partition and perform a fresh installation. For more information on partitions and how to set them up, refer to Section 9.13, “Disk Partitioning Setup”.
If you choose to upgrade your system using the installation program, any software not provided by Red Hat Enterprise Linux that conflicts with Red Hat Enterprise Linux software is overwritten. Before you begin an upgrade this way, make a list of your system's current packages for later reference: 
rpm -qa --qf '%{NAME} %{VERSION}-%{RELEASE} %{ARCH}\n' > ~/old-pkglist.txt
After installation, consult this list to discover which packages you may need to rebuild or retrieve from sources other than Red Hat.
Next, make a backup of any system configuration data: 
su -c 'tar czf /tmp/etc-`date +%F`.tar.gz /etc' 
su -c 'mv /tmp/etc-*.tar.gz /home'
Make a complete backup of any important data before performing an upgrade. Important data may include the contents of your entire /home directory as well as content from services such as an Apache, FTP, or SQL server, or a source code management system. Although upgrades are not destructive, if you perform one improperly there is a small possibility of data loss.

Warning

Note that the above examples store backup materials in a /home directory. If your /home directory is not a separate partition, you should not follow these examples verbatim! Store your backups on another device such as CD or DVD discs or an external hard disk.
For more information on completing the upgrade process later, refer to Section 35.2, “Finishing an Upgrade”.