Red Hat Knowledgebase

If you have an active Red Hat Enterprise Linux subscription, you can migrate your system at no additional cost.

Best Choice: Administrator-Guided Migration

The safest method to migrate from an earlier Red Hat release is an administrator-guided migration. In this migration method, the system administrator:

• Evaluates the currently deployed system
• Backs up the deployed configuration data, user data, and software applications to an external system
• Performs a fresh install of Red Hat Enterprise Linux 4
• Restores the required configuration data, user data, and software applications

Red Hat officially supports administrator guided migrations for commercial deployments, as this method provides the highest probability of a successful migration.

WARNING: Use of the "upgrade" option during the installation process can cause erratic system behavior in various cases and is unsupported by Red Hat. If you experience problems with an upgraded system and are seeking assistance from Red Hat Support, you will be instructed to perform a clean installation.

Second Choice: Automated Migration (not recommended)

Red Hat Enterprise Linux 4 also includes support for automated migrations from earlier Red Hat Enterprise Linux releases. An automated migration is implemented by Anaconda, the Red Hat Enterprise Linux 4 installer. Red Hat does not recommend an automated migration, as it provides a lower probability of success than do administrator-guided migrations. Red Hat technical support provides assistance only with automated migrations from the most recent previous release of Red Hat Enterprise Linux. The Red Hat Enterprise Linux 4 installer warns you about upgrading from any release earlier than Red Hat Enterprise Linux 3, but still allows you to proceed at your discretion.

Red Hat Enterprise Linux 4 avoids incomplete migrations. The Red Hat Enterprise Linux automated upgrade capability handles only the upgrade of system components distributed with the Red Hat Enterprise Linux base operating system. Automated upgrades may impact non-standards-conforming third-party applications in unspecified ways, some of which may not be found until you run the application. By establishing a clean baseline and then reinstalling third-party applications using their native installation tool on a fresh system, application-install time-dependency checking can be employed to ensure that a complete runtime environment is available for all third-party software.

For more information on upgrading to Red Hat Enterprise Linux 4, refer to the following document: http://www.redhat.com/f/pdf/rhel4/UpgradeGuidelines.pdf