Chapter 37. Upgrading Your Current System

Red Hat does not support upgrades from earlier major versions

Red Hat does not support in-place upgrades between any major versions of Red Hat Enterprise Linux. A major version is denoted by a whole number version change. For example, Red Hat Enterprise Linux 5 and Red Hat Enterprise Linux 6 are both major versions of Red Hat Enterprise Linux.

In-place upgrades across major releases do not preserve all system settings, services or custom configurations. Consequently, Red Hat strongly recommends fresh installations when upgrading from one major version to another.

Although upgrading from Red Hat Enterprise Linux 5 is technically possible, you are more likely to have a consistent experience by backing up your data and then installing this release of Red Hat Enterprise Linux 6 over your previous Red Hat Enterprise Linux installation.

Upgrading your system installs updated versions of the packages which are currently installed on your system.

The upgrade process preserves existing configuration files by renaming them with an .rpmsave extension (for example, sendmail.cf.rpmsave). The upgrade process also creates a log of its actions in /root/upgrade.log.

However, note the following limitations before you choose to upgrade your system:

Individual package configuration files may or may not work after performing an upgrade due to changes in various configuration file formats or layouts.
If you have one of Red Hat's layered products (such as the Cluster Suite) installed, it may need to be manually upgraded after the Red Hat Enterprise Linux upgrade has been completed.
Third party or ISV applications may not work correctly following the upgrade.

Procedure 37.1. Upgrading Your System

Bring your system up to date using RHN.
Back up any important data on the system.
Reboot the system from a Red Hat Enterprise Linux 6 installation DVD or minimal boot media.
Press the Esc key during the first 60 seconds to access the boot: prompt.
Enter the kernel option linux upgradeany at the boot: prompt.
Proceed with a normal installation as described in Chapter 9, Installing using anaconda for the x86 architecture, Chapter 16, Installing using anaconda for the POWER architecture, and Chapter 23, Installation Phase 3: Installing using anaconda for IBM System z until you reach a dialog that notifies you that At least one existing installation has been detected on your system.
Follow the instructions in Section 9.11, “ Upgrading an Existing System ” for the x86 architecture, Section 16.13, “ Upgrading an Existing System ” for the POWER architecture, and Section 23.12, “ Upgrading an Existing System ” for System z as though you were updating between minor versions.

Some upgraded packages may require the installation of other packages for proper operation. If you choose to customize your packages to upgrade, you may be required to resolve dependency problems. Otherwise, the upgrade procedure takes care of these dependencies, but it may need to install additional packages which are not on your system.

Depending on how you have partitioned your system, the upgrade program may prompt you to add an additional swap file. If the upgrade program does not detect a swap file that equals twice your RAM, it asks you if you would like to add a new swap file. Refer to the recommendations in Section 9.14.5, “Recommended Partitioning Scheme” for x86 systems, Section 16.16.5, “Recommended Partitioning Scheme” for POWER systems, or the resources for System z listed in Section 23.15.5, “Recommended Partitioning Scheme” to determine whether you should add swap space.