Convert2RHEL FAQ (Frequently Asked Questions)

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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
Migrate from CentOS to Red Hat Enterprise Linux
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
AlmaLinux OS 8 RHEL 8 64-bit Intel
Rocky 8 RHEL 8 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 irreversible changes are made to the system.

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

No. Since Convert2RHEL version 1.2 there is no longer capability to convert CentOS Linux 6 or Oracle Linux 6 to RHEL 6.

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?

Yes, it is possible to perform an unsupported conversion from CentOS Stream 8 to RHEL 8. For information about unsupported conversions, see How to perform an unsupported conversion from a RHEL-derived Linux distribution to RHEL.

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?

Using Convert2RHEL is supported for converting cloud instances on AWS, Azure, and GCP with two notable exclusions:
- Convert2RHEL cannot be used to access packages provided by the Red Hat Update Infrastructure (RHUI).
- Converting images with associated software cost is not supported.
You can convert the instance either using an annual Red Hat Enterprise Linux subscription or using an hourly-priced pay-as-you-go subscription. The latter is available only for CentOS Linux 7 instances though.
Conversions on other cloud providers are likely to work but haven't been tested by Red Hat.

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.

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