Red Hat SummitChapter 2. Planning an upgrade to RHEL 9
Before beginning your upgrade from RHEL 8 to RHEL 9, review system requirements, limitations, and other considerations.
2.1. Planning an upgrade from RHEL 8 to RHEL 9
An in-place upgrade is the recommended and supported way to upgrade your system to the next major version of RHEL.
You should consider the following before upgrading to RHEL 9:
Operating system - The operating system is upgradable by the
Leapputility under the following conditions:The source OS version is installed on a system with one of the following supported architectures:
- 64-bit Intel, AMD, and ARM
- IBM POWER (little endian)
64-bit IBM Z
For more information, see Red Hat certified hardware.
- Minimum hardware requirements for RHEL 9 are met.
- You have access to up-to-date content for the selected source and target OS versions. See Preparing a RHEL 8 system for the upgrade for more information.
Applications - You can migrate applications installed on your system using
Leapp. However, in certain cases, you have to create custom actors, which specify actions to be performed byLeappduring the upgrade, for example, reconfiguring an application or installing a specific hardware driver. For more information, see Handling the migration of your custom and third-party applications. Note that custom actors are unsupported by Red Hat.ImportantThe SHA-1 algorithm has been deprecated in RHEL 9. If your system contains any packages with RSA/SHA-1 signatures, the upgrade is inhibited. Before upgrading, either remove these packages or contact the vendor for packages with RSA/SHA-256 signatures. For more information, see SHA-1 deprecation in Red Hat Enterprise Linux 9.
Security - You should evaluate this aspect before the upgrade and take additional steps when the upgrade process completes. Consider especially the following:
- Before the upgrade, define the security standard your system has to comply with and understand the security changes in RHEL 9.
-
During the upgrade process, the
Leapputility sets SELinux mode to permissive. -
Leappsupports in-place upgrades of RHEL 8.8 and later systems in Federal Information Processing Standard (FIPS) 140 mode to RHEL 9 FIPS-mode-enabled systems. FIPS mode stays enabled during the complete upgrade process. - After the upgrade is finished, re-evaluate and re-apply your security policies. For information about applying and updating security policies, see Applying security policies.
Storage and file systems
Backup - You should always back up your system prior to upgrading. For example, you can use the Relax-and-Recover (ReaR) utility, LVM snapshots, RAID splitting, or a virtual machine snapshot.
NoteFile systems formats are intact. As a consequence, file systems have the same limitations as when they were originally created.
- Encryption - Systems with encrypted storage can be upgraded if the storage uses the LUKS2 format configured with the Clevis TPM 2.0 token. For more information, see Configuring manual enrollment of LUKS-encrypted volumes by using a TPM 2.0 policy.
- High Availability - If you are using the High Availability add-on, follow the Recommended Practices for Applying Software Updates to a RHEL High Availability or Resilient Storage Cluster Knowledgebase article.
- Downtime - The upgrade process can take from several minutes to several hours.
Satellite
- Client - If you manage your hosts through Satellite, you can upgrade multiple hosts simultaneously from RHEL 8 to RHEL 9 using the Satellite web UI. For more information, see Upgrading Hosts to Next Major Red Hat Enterprise Linux Release.
- Server and Capsule - You can upgrade Satellite Servers and Capsules starting in Satellite 6.16. For more information, see Upgrading Satellite or Capsule to RHEL 9 in-place by using Leapp.
- SAP HANA - If you are using SAP HANA, follow the Upgrading SAP environments from RHEL 8 to RHEL 9 guide instead. Note that the upgrade path for RHEL with SAP HANA might differ.
- RHEL for Real Time - Upgrades on real-time systems are supported.
- Real Time for Network Functions Virtualization (NFV) in Red Hat OpenStack Platform - Upgrades on real-time systems are supported.
Public clouds
- Pay-As-You-Go - The in-place upgrade is supported for on-demand Pay-As-You-Go (PAYG) instances that use Red Hat Update Infrastructure (RHUI) on Amazon Web Services (AWS) on all supported architectures, and on Google Cloud and Microsoft Azure only on the Intel architecture.
- Bring Your Own Service - The in-place upgrade is supported for Bring Your Own Subscription instances on all public clouds that use RHSM for a RHEL subscription.
-
Language - All
Leappreports, logs, and other generated documentation are in English, regardless of the language configuration. - Boot loader - It is not possible to switch the boot loader from BIOS to UEFI on RHEL 8 or RHEL 9. If your RHEL 8 system uses BIOS and you want your RHEL 9 system to use UEFI, perform a fresh install of RHEL 9 instead of an in-place upgrade. For more information, see Is it possible to switch the BIOS boot to UEFI boot on preinstalled Red Hat Enterprise Linux machine?
Known limitations - Notable known limitations of
Leappcurrently include:- Network based multipath and network storage that use Ethernet or Infiniband are not supported for the upgrade. This includes SAN using FCoE and booting from SAN using FC. Note that SAN using FC are supported.
- The in-place upgrade is not supported for systems with Ansible Automation Platform installed. To use a RHEL 8 Ansible Automation Platform installation on RHEL 9, see the How do I migrate my Ansible Automation Platform installation from one environment to another? Knowledgebase solution.
- Red Hat JBoss Enterprise Application Platform (EAP) is not supported for the upgrade to RHEL 9. You must manually install and configure JBoss EAP on your system after the upgrade. For more information, see the Red Hat Knowledgebase solution In-place Migrating of Jboss EAP and websphere servers along with Linux using leapp utility.
See also Known Issues.
You can use Red Hat Lightspeed to determine which of the systems you have registered to Red Hat Lightspeed is on a supported upgrade path to RHEL 9. To do so, navigate to the respective Advisor recommendation in Red Hat Lightspeed, enable the recommendation under the Actions drop-down menu, and inspect the list under the Affected systems heading. Note that the Advisor recommendation considers only the RHEL 8 minor version and does not perform a pre-upgrade assessment of the system. See also Advisor-service recommendations overview.
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