This article describes how an administrator can migrate Red Hat Enterprise Linux 5 or Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7 with the help of the Preupgrade Assistant. The Preupgrade Assistant is a tool which assesses your running system for anything that might adversely affect the success of your migration.
As Red Hat Enterprise Linux 5 will have only extended update support after March 2017, administrators will find a tool like that useful to help them migrate their systems to Red Hat Enterprise Linux 7. The migration from Red Hat Enterprise Linux 5 to Red Hat Enterprise Linux 6 is not covered by the Preupgrade Assistant, nor is it planned.
Note: The Preupgrade Assistant can also be used for the in-place upgrade from Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7 but this is out of scope of this article. The in-place upgrade from Red Hat Enterprise Linux 5 to Red Hat Enterprise Linux 7 is neither supported nor planned.
Migration is a clean installation of a system on a new machine with the configuration as close as possible to the original system, which remains untouched.
As many administrators know, manual migration can be quite complicated, tedious, and error-prone. Several questions arise:
- Is it possible to make it easier?
- Is there an easy way to do it faster?
- Do we have a tool for it?
The answer is "yes", but only semi-automated migrations are supported at the moment . The Preupgrade Assistant tool is designed to provide all of that, helping administrators with the migration of Red Hat Enterprise Linux 5 or Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7.
Supported Red Hat Enterprise Linux variants
Nowadays, only the Server variant is supported. Of course, the Preupgrade Assistant is able to migrate Red Hat Enterprise Linux 5 32bit to Red Hat Enterprise Linux 7 64bit. Other variants (such as Workstation, Client or Compute Node) are not in our focus yet.
How the Preupgrade Assistant works
The assessment of the original system is provided by a set of scripts called modules which check various parts of the original system, for example installed packages, the disk layout, the network configuration and so on.
The set of modules is constantly growing and the modules can even be created by administrators themselves. We provide a tool for the module creation.
The Preupgrade Assistant runs the modules and generates a report from the assessment as an HTML file located at /root/preupgrade/results.html. Administrators have to read it carefully and take the appropriate actions to change the system configurations (if needed).
These modules also collect data for the generation of Kickstart, which will be described later.
We would like to stress that the migration is not fully automated and the administrator has to go through the results and review them before proceeding with the migration.
The Preupgrade Assistant generates the Kickstart file based on the configuration of the original Red Hat Enterprise Linux 5 or Red Hat Enterprise Linux 6 system. The Kickstart file answers the questions usually asked by the installation program, such as your time zone, information about packages needed to be installed, disk partitioning and so on. It can be used for a clean installation of Red Hat Enterprise Linux 7 , after the review and corrections were done by the administrator. These two steps (the review and corrections) MUST be taken before the installation.
Administrators should modify the Kickstart file according to the Red Hat Enterprise Linux 7 installation manual .
The Preupgrade Assistant source codes are available on GitHub .
For more information look at a Knowledge base article provided by Red Hat .
In case of any questions, our team is available to help you via IRC on #preupgrade channel on freenode.
-  https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Installation_Guide/
-  https://github.com/upgrades-migrations/preupgrade-assistant
-  https://access.redhat.com/solutions/1468623