The installation process for Red Hat Linux 4.2 includes the ability to upgrade from prior versions of Red Hat Linux (2.0, 2.1, 3.0.3, 4.0, and 4.1) which are based on RPM technology. Upgrading your system installs the modular 2.0.x kernel as well as updated versions of the packages which are installed on your machine. The upgrade process preserves existing configuration files using a .rpmsave extenstion (e.g., sendmail.cf.rpmsave) and leaves a log telling what actions it took in /tmp/upgradelog. As software evolves, configuration file formats can change, so you should carefully compare your original configuration files to the new files before integrating your changes.

To upgrade a Red Hat Linux system, you must use a boot floppy (and possibly a supplemental floppy), just as if you were performing a full install. After selecting the medium to install from (and setting up networking information if it's required), the installation procedure prompts you to either Install or Upgrade; select Upgrade. This upgrade procedure is the functional equivalent of running the upgrade script in prior versions of Red Hat Linux.

Please note that some upgraded packages may ``depend'' on other packages which may not be installed on your system. The upgrade procedure takes care of these dependencies, but it may need to install additional packages in order to satisfy them.