EL 8 to EL 9 Upgrade

Upgrading from EL 8 (CentOS 8, AlmaLinux 8, Rocky Linux 8) to EL 9 is a major version upgrade. This guide covers the full process using the Leapp and ELevate tools.

Overview

Upgrade Paths

Source	Target	Tool
CentOS 8 / CentOS Stream 8	AlmaLinux 9 / Rocky Linux 9	ELevate
AlmaLinux 8	AlmaLinux 9	Leapp / ELevate
Rocky Linux 8	Rocky Linux 9	Leapp / ELevate

Prerequisites

System is updated to the latest EL 8 minor release
At least 2 GB of free disk space (on /var)
A reliable full system backup
Physical or remote console access (not just SSH)

Preparation

Update the Current System

dnf update -y
reboot

Verify the Current System Version

cat /etc/redhat-release
uname -r

Create a Full Backup

# Back up /etc
tar czf /root/etc-backup-$(date +%Y%m%d).tar.gz /etc/

# Save the list of installed packages
rpm -qa --qf '%{NAME}\n' | sort > /root/installed-packages-el8.txt

# Save partition table
fdisk -l > /root/partition-table.txt

# Back up boot configuration
cp -a /boot/grub2/ /root/grub2-backup/

Installing the ELevate Tools

Install the elevate-release Package

dnf install -y http://repo.almalinux.org/elevate/elevate-release-latest-el8.noarch.rpm

Install Leapp and Upgrade Data

Install the data package corresponding to your target system:

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

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

dnf install -y leapp-upgrade leapp-data-centos

Pre-Upgrade Assessment

Run the Pre-Upgrade Check

leapp preupgrade

This generates a detailed report listing all issues that must be addressed.

Review the Pre-Upgrade Report

cat /var/log/leapp/leapp-report.txt

Common Blocking Issues and Solutions

Issue: Deprecated Repositories Detected

# Disable incompatible third-party repos
dnf config-manager --disable <repo-name>

Issue: PAM Configuration Incompatible

leapp answer --section authselect_check.confirm=True

Issue: GRUB Device Detection Failure

echo 'GRUB_DEVICE=/dev/sda' >> /etc/default/leapp

Issue: Custom Kernel Modules Detected

rmmod <module-name>
# Also remove the corresponding config from /etc/modules-load.d/

Handling Third-Party Packages

dnf list installed | grep -v '@baseos' | grep -v '@appstream'

# Add packages to remove during upgrade
echo "custom-package-name" >> /etc/leapp/transaction/to_remove

# Add packages to keep during upgrade
echo "package-to-keep" >> /etc/leapp/transaction/to_keep

Performing the Upgrade

Start the Upgrade Process

leapp upgrade

The upgrade process takes considerable time. Be patient.

Reboot into the Upgrade Environment

reboot

Post-Upgrade Checks

Verify the System Version

cat /etc/redhat-release
uname -r
rpm -q kernel-core

Check System Service Status

systemctl --failed

Verify Network Connectivity

ip addr show
nmcli connection show
ping -c 3 8.8.8.8

Verify Repository Configuration

dnf repolist
dnf check-update

Clean Up Upgrade Artifacts

# Remove upgrade-related packages
dnf remove -y leapp-upgrade leapp-data-* elevate-release

# Remove old EL 8 kernels
dnf remove -y $(rpm -qa | grep el8 | grep kernel)

# Remove Leapp leftover data
rm -rf /var/log/leapp /root/tmp_leapp_py3

Rebuild the RPM Database

rpm --rebuilddb

Reset SELinux Labels

fixfiles -B onboot
reboot

Known Issues

Network Configuration Changes

EL 9 defaults to the NetworkManager key-file format instead of the legacy ifcfg format.

nmcli connection migrate

SSH Configuration Changes

EL 9 disables some legacy cryptographic algorithms by default.

update-crypto-policies --show

If temporary compatibility with older clients is needed:

update-crypto-policies --set DEFAULT:SHA1

Python Version Changes

EL 9 ships Python 3.9 by default. Python 2 is no longer available.

python3 --version
alternatives --list | grep python

PHP Module Stream Changes

dnf module list php
dnf module reset php
dnf module enable php:8.1

Application Compatibility Checks

Check Dynamic Library Dependencies

for bin in /usr/local/bin/*; do
    ldd "$bin" 2>&1 | grep "not found" && echo "  --> $bin"
done

Validate systemd Service Files

systemd-analyze verify /etc/systemd/system/*.service 2>&1 | grep -v "^$"

Compare Pre- and Post-Upgrade Package Lists

rpm -qa --qf '%{NAME}\n' | sort > /root/installed-packages-el9.txt
diff /root/installed-packages-el8.txt /root/installed-packages-el9.txt

Handling Upgrade Failures

If the upgrade process is interrupted or fails:

Check Upgrade Logs

cat /var/log/leapp/leapp-upgrade.log
journalctl -b -p err

Restore from Snapshot

If you created an LVM snapshot or VM snapshot beforehand, restoring it is the most reliable rollback method.

lvconvert --merge /dev/vg0/pre-upgrade-snap
reboot