In-Place Upgrade from EL8 to EL9

This article provides a step-by-step walkthrough to perform an in-place upgrade from Enterprise Linux 8 (Oracle Linux 8, RHEL 8, AlmaLinux 8, Rocky Linux 8) to Enterprise Linux 9.

Prerequisites:

• Kindly take the Proper snapshot backup and all the configurations and db dumps backups Before the activity.
  Ensure the EL8 Server is fully updated to latest. 
• Allow the Repository of EL9 for the Major Version Upgrade in Network level(Dont' map in server, Upgrade Tool will handle those)
• Allow Leapp tool from appstream and ELevate from External RPM as per the requirement.
• Have Enough Space Before the Activity in / and /var partition. 
• Disable the Agents which are running in the Server along with Antivirus Agents.
• Clear the Old remnants files from EL7 if available
• Kindly upgrade the Jetpatch applications to latest to avoid conflicts Before the Upgrade. Kindly reach out to us for the RPM.

We will use **Leapp** (Red Hat's native tool) for RHEL systems. For community clones like Oracle, Alma, and Rocky Linux, we will use **ELevate** (a community framework built on top of Leapp).

Preupgrade Installation:
Redhat Preupgrade: 

Ensure the subscription before runnning the Leapp.

Then Install the Leapp-upgrade 

#dnf install -y leapp-upgrade

ELevate Preupgrade:

Install the ELevate package, 

#yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el$(rpm --eval %rhel).noarch.rpm

Then install the leapp packages, 

For Alma

#dnf install -y leapp-upgrade leapp-data-almalinux

For Rocky

#dnf install -y leapp-upgrade leapp-data-rocky

For Oracle

#dnf install -y leapp-upgrade leapp-data-oraclelinux

Pre-upgrade simulation :

Let's run the preupgrade check by 

#leapp preupgrade

This will Give verify the kernel modules, packages and compatibility for the upgrade. 

Look for the outputfile and clear the inhibitors and blockers fully. 

Clearing Inhibitors:

If you are getting inhibitors related to nginx, postgres and Intigua, 

Kindly take the proper backups and disable the services #systemctl disable <service_name>

Then uninstall the mentioned packages in leapp-report.txt.

After the upgrade, We need to restore all the removed packages. 

OS Major Upgrade:

After all the inhibitors were cleared, You can proceed with actual upgrade, 

#leapp upgrade 

This will download the all the required Packages which are required for Upgrade. 

Once you able to see "Reboot the system to continue with the upgrade"

Kindly reboot the server, which will perform the upgrade and starts the server.

Verification and Clean-up:

Once the Systems comes back live, Check the release, 

#cat /etc/os-release

Check for the applications and agents/services and other required data were up and running. 

We can start the stopped the Antivirus agents and other services.

Once verified, We can proceed for clean up.

You can clean up the old Remnants packages and files by, 

#leapp cleanup

#dnf autoremove -y

Clear the dnf cache to downlaod the latest files by 

#dnf clean all && dnf update -y

Reinstallation of Packages:

Let's install the Packages to restore the application which we are removed like nginx, postgres, Intigua packages.

For Postgres: 

Change the version as per the requirement.

Install the repository RPM:

# sudo dnf install -y https://download.postgresql.org/pub/repos/yum/reporpms/EL-9-x86_64/pgdg-redhat-repo-latest.noarch.rpm
Install PostgreSQL:

#sudo dnf install -y postgresql16-server

Optionally initialize the database and enable automatic start:

#sudo /usr/pgsql-16/bin/postgresql-16-setup initdb

#sudo systemctl enable postgresql-16

#sudo systemctl start postgresql-16

For Nginx:

#dnf install -y nginx

For Intigua: 

Install the same versions before the upgrade.

Via the RPMs

#dnf localinstall intigua*

Via Live Repo:

#dnf install intigua*

Restoration:

Once everything installed, Kindly restore the intigua.properties 

#cp -rp /backup_path/intigua.properties /usr/share/tomcat/default/conf/intigua.properties

Then restart the Tomcat. 

#systemctl restart tomcat.

JetPatch Verification:

Restart of Tomcat will bring up the application as like before. 
Verify all the functionalities, RPs and connectivity. 

If any error throws up, Kindly restore the snapshot, and reach out to us.