Chapter 2. Preparing for a RHEL conversion

This procedure describes the steps that are necessary before performing the conversion from CentOS Linux or Oracle Linux to Red Hat Enterprise Linux (RHEL).

Prerequisites

  • You have verified that your system is supported for conversion to RHEL. See Supported conversion paths for more information.
  • You have stopped important applications, database services, and any other services that store data to reduce the risk of data integrity issues.
  • You have temporarily disabled antivirus software to prevent the conversion from failing.
  • You have disabled or adequately reconfigured any configuration management system (such as Salt, Chef, Puppet, Ansible) to not attempt to restore the original system.

Procedure

  1. Back up your system and verify that you can restore your system.
  2. Check Known issues and limitations and verify that your system is supported for conversion. Apply workarounds where applicable.
  3. Ensure that the standard kernel is the booted kernel:

    • CentOS Linux: the standard CentOS Linux kernel
    • Oracle Linux: the Red Hat Compatible Kernel (RHCK)

      If the kernel your system is booted into is not the standard kernel, for example CentOS realtime kernel or Oracle Linux Unbreakable Enterprise Kernel (UEK), change the default kernel to the standard kernel and reboot your system.

  4. Install Convert2RHEL:

    1. Download the Red Hat GPG key:

      # curl -o /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release https://www.redhat.com/security/data/fd431d51.txt
    2. Download the SSL certificate of the https://cdn.redhat.com server, which contains the Convert2RHEL repositories:

      # curl --create-dirs -o /etc/rhsm/ca/redhat-uep.pem https://ftp.redhat.com/redhat/convert2rhel/redhat-uep.pem
    3. Install the Convert2RHEL repository file:

      # curl -o /etc/yum.repos.d/convert2rhel.repo https://ftp.redhat.com/redhat/convert2rhel/version_number/convert2rhel.repo

      Replace version_number with the appropriate major version of the OS, for example 7 or 8.

      Note

      You must perform the conversion with the latest version of the Convert2RHEL repository file. If you had previously installed an earlier version of the repository file, remove the earlier version and install the current version.

    4. Install the Convert2RHEL utility:

      # yum -y install convert2rhel
  5. Ensure you have access to RHEL packages through one of the following methods:

    1. Red Hat Content Delivery Network (CDN) through Red Hat Subscription Manager (RHSM). You must have a Red Hat account and an appropriate RHEL subscription to access RHSM. Note that the OS will be converted to the corresponding minor version of RHEL per Table 1.1.
    2. Red Hat Satellite in a version that has Full or Maintenance support. For more information, see Red Hat Satellite Product Life Cycle.

      Note

      Ensure that the Satellite server meets the following conditions:

      • Satellite has a subscription manifest with RHEL repositories imported. For more information, see the Managing Subscriptions chapter in the Content Management Guide for the particular version of Red Hat Satellite, for example, for version 6.8.
      • All required repositories are enabled and synchronized with the latest RHEL 7.9 or RHEL 8.4 updates and published on Satellite. Enable at minimum the following repositories for the appropriate major version of the OS:

        • Red Hat Enterprise Linux 7 Server RPMs x86_64 7Server
        • Red Hat Enterprise Linux 8 for x86_64 - AppStream RPMs 8.4
        • Red Hat Enterprise Linux 8 for x86_64 - BaseOS RPMs 8.4
    3. Custom repositories configured in the /etc/yum.repos.d/ directory and pointing to a mirror of the RHEL 7.9 or RHEL 8.4 repositories. Use custom repositories for systems that can connect to only local networks and cannot therefore access Red Hat CDN through RHSM. Make sure that the repositories contain the latest content available for that RHEL minor version to prevent downgrading and potential conversion failures. For more information, see Creating a Local Repository and Sharing With Disconnected/Offline/Air-gapped Systems.

      Note

      RHEL 8 content is distributed through two default repositories, BaseOS and AppStream. If you are accessing RHEL packages through custom repositories, you must configure both default repositories for a successful conversion. When running the Convert2RHEL utility, make sure to enable both repositories using the --enablerepo option. For more information about RHEL 8 repositories, see Considerations in adopting RHEL 8.

  6. If you are accessing RHEL packages through a Red Hat Satellite server, download the consumer RPM to the /usr/share/convert2rhel/subscription-manager/ directory:

    # curl --insecure --output /usr/share/convert2rhel/subscription-manager/katello-ca-consumer-latest.noarch.rpm https://satellite.example.com/pub/katello-ca-consumer-latest.noarch.rpm

    Replace satellite.example.com with the hostname of your Satellite server.

  7. Update the original OS to the minor version supported for conversion as specified in Table 1.1 and then reboot the system.

    You must perform the conversion with the latest packages from the minor version of the OS that is supported for conversion to use the rollback feature in case the conversion fails. For more information, see Conversion rollback.