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Convert2RHEL FAQ (Frequently Asked Questions)

Updated 2021-05-26T23:18:46+00:00

Overview

This article provides answers to some of the most frequently asked questions regarding the Convert2RHEL utility and support related topics, as well as other topics related to how to migrate to a supported Red Hat Enterprise Linux (RHEL) installation.

What is Convert2RHEL?

Convert2RHEL is an officially supported component of RHEL that enables the conversion of select RHEL derivative distributions into a supportable RHEL state, retaining existing applications and configurations.

Where can I learn more about using Convert2RHEL?

Official Documentation
Support Policy
FAQ
Upstream project and source code

What operating systems are supported for converting to RHEL?

The authoritative list is documented in Chapter 1. Supported conversion paths. Today, these include:

Source OS Target OS Architecture
CentOS Linux 8 RHEL 8 64-bit Intel
CentOS Linux 7 RHEL 7 64-bit Intel
Oracle Linux 8 RHEL 8 64-bit Intel
Oracle Linux 7 RHEL 7 64-bit Intel

Are other linux kernels supported, such as CentOS Linux RealTime or Oracle's UEK kernels?

No, only kernels equivalent to the regular RHEL kernel are supported. The tool will detect for non-supported kernels and foreign kernel modules (drivers) and stop, guiding the user to restart using a supported kernel. CentOS Linux systems should be rebooted into the default, standard CentOS Linux kernel. Oracle Linux systems should be restarted into Oracle's "Red Hat Compatible Kernel" instead of Oracle's UEK kernel. This step ensures that the system is functional with RHEL compatible kernels before any unreversible changes are made to the system.

Can CentOS Linux 6 or Oracle Linux 6 be converted to RHEL 6?

Red Hat does not officially support conversions to RHEL 6 as its Maintenance Support 2 Phase has ended as defined in the RHEL Life Cycle policy. While there is an Extended Life-cycle Support add-on which can be purchases, the support policy excludes “new deployments of RHEL 6”.

That said, previous versions of the tool have enabled this and has been used successfully by Red Hat Consulting services with multiple large customers. It is possible to ask Sales to request a support exception to consider this as an option for the purpose of in-place upgrades from RHEL 6 to RHEL 7.

Note that new capabilities added to Convert2RHEL will not be tested for RHEL 6 conversions and this capability will be removed in a future release. Previous versions would still be accessible for use, but not supported by Red Hat. The guide How to convert from CentOS Linux 6 or Oracle Linux 6 to RHEL explains that while not supported, it is possible to use the utility.

Can other operating systems such as Windows, SUSE, Debian, Ubuntu, or other Linux distributions be converted to RHEL?

No, only RHEL derivative (clone) Linux operating systems. Even with other RPM based distributions such as SUSE Linux, there are low level technology differences, such as third party application library requirements and file system technologies, that prevent this type of conversion. Instead, Red Hat recommends a “migration” strategy in which new RHEL systems are installed and configured, applications installed and configured, and data copied over. Visit our RHEL Migration Process landing page which lists multiple migration options, as well as Red Hat Consulting services who can provide assistance.

Can CentOS Stream be converted to RHEL?

At this time Convert2RHEL does not convert CentOS Stream 8 to RHEL 8. This may be evaluated in the future but it is unclear if there are actual use cases and demand for this. Today, all attention is focused on supporting various use cases for the currently supported options. Additionally, because CentOS Stream represents a future state of RHEL and may include packages that do not yet exist in a current release, this presents a potential downgrade scenario. Downgrades are known to present issues as RPM scriptlets executed at install/update time are typically not idempotent and easily reversible. There can also be library and low level metadata compatibility issues. These support concerns are further discussed in How to use yum to downgrade or rollback some package updates? In general, Red Hat does not recommend RHEL minor release downgrades, such as 7.9 to 7.8, for these reasons.

Can CentOS Stream 8 be upgraded to CentOS Stream 9 or RHEL 9?

Possibly, but the Convert2RHEL utility will not be used. Instead, the LEAPP utility provides advanced and automated in-place upgrades from RHEL 7 to RHEL 8 at scale.

How long does the conversion process take?

Essentially the process is roughly equivalent to a RHEL minor release upgrade in which every RHEL RPM package on the system is replaced. Third party and non-Red Hat packages are not replaced. Therefore, the amount of time can vary depending on how many packages need replaced, network speed, storage speed, and similar variables. A good analogy is to ask your own staff, “How quickly can we apply minor updates and reboot the system for a single node as well as many nodes at once”. A minimal CentOS install in a virtual machine typically takes around 20 minutes, but this is dependent on the environment.

Can Convert2RHEL be used with cloud images, such as for AWS, Azure, GCP, and similar?

This depends on how you are using the cloud. If you are using pre-built, on demand images, there is not need - simply switch to using a RHEL base image in your cloud provider’s marketplace. If you are uploading custom build images, then Convert2RHEL should work, however it is not yet tested in our automated framework as there are so many different ways that a user could generate these. We recommend that you first consider using RHEL Image Builder to recreate a pure cloud image from scratch and customize that. But you are welcome to make a copy of your custom cloud image and test Convert2RHEL with it. As long as copies are made, there should be no issues.

Can Ansible Automation Platform automate these conversions?

There is no direct integration, modules, or collections for Convert2RHEL. However, there is a proof of concept playbook in the upstream project demonstrating how easily it could automate installation at scale. Note that the final conversion step would be a call out to the shell module which can take an undetermined amount of time, as described above. Therefore, careful planning would be required for planning an appropriate level of parallelism from Tower.

Can Red Hat Satellite server perform these conversions?

Partially. With an extra step as defined in Chapter 3. Converting to a RHEL system, it explains how Convert2RHEL can register the system to Satellite and pull the RHEL content for the conversion. The Ansible Playbook mentioned above could be used to help install Convert2RHEL and initiate the process.

We are exploring a future Satellite enhancement to include a Job template and ansible playbook so that Satellite could better initiate conversions at scale.

Can I convert large environments of tens of thousands of systems?

Yes, we have multiple enterprise customers who have successfully converted tens of thousands of systems to RHEL! The questions above regarding Red Hat Satellite and Ansible Automation Platform are Red Hat’s management solutions for managing and automating large environments.

Can I convert systems running [Some_Application]

The only content and applications tested are what is provided in official RHEL content repositories. Typically the binary compatibility results in no issues, but there are possibilities for incompatibilities. It is always recommended to make backups before conversions as directed in the documentation. Additionally, it is recommended to test critical third party applications for compatibility after conversion. Support regarding third party applications, including third party kernel modules (drivers) is defined in Red Hat support policy regarding third party packages in RHEL.