This document outlines the step-by-step process of upgrading a RHEL 8 system to RHEL 9, including package removal, kernel configuration, and bootloader management.

---

Step 1: Identifying Installed RHEL 8 Packages

Before upgrading, identify and list all installed packages specific to RHEL 8.

rpm -qa | grep -e '\.el[78]' | grep -vE '^(gpg-pubkey|libmodulemd|katello-ca-consumer)' | sort

Explanation:

• rpm -qa lists all installed RPM packages.
• grep -e '\.el[78]' filters packages from RHEL 7 and RHEL 8.
• grep -vE '^(gpg-pubkey|libmodulemd|katello-ca-consumer)' excludes system key and module-related packages.
• sort arranges the output for easy review.

To count the number of RHEL 8-specific packages:

rpm -qa | grep -e '\.el[78]' | grep -vE '^(gpg-pubkey|libmodulemd|katello-ca-consumer)' | sort | wc -l

This will return the total count of relevant packages.

---

Step 2: Exporting Package List and Removing RHEL 8 Packages

Before removing, save the package list:

rpm -qa | grep -e '\.el[78]' | grep -vE '^(gpg-pubkey|libmodulemd|katello-ca-consumer)' | sort >> rhel8pkg.txt

This ensures that you have a backup reference of the packages being removed.

To remove these packages, execute:

dnf remove $(cat rhel8pkg.txt)

Explanation:

• dnf remove uninstalls packages.
• $(cat rhel8pkg.txt) feeds the package list into the command.

---

Step 3: Cleaning Up Upgrade-Related Files

Remove any residual upgrade files that might interfere with the upgrade:

rm -rf /var/log/leapp /root/tmp_leapp_py3 /var/lib/leapp

Explanation:

• rm -rf forcefully deletes unnecessary files and logs generated by the leapp upgrade tool.

---

Step 4: Updating Kernel Boot Parameters

Modify kernel boot options to reflect necessary configurations:

BOOT_OPTIONS="$(tr -s "$IFS" '\n' </proc/cmdline | grep -ve '^BOOT_IMAGE=' -e '^initrd=' | tr '\n' ' ')"
echo $BOOT_OPTIONS > /etc/kernel/cmdline

Explanation:

• tr -s "$IFS" '\n' </proc/cmdline converts the /proc/cmdline parameters into a newline-separated format.
• grep -ve '^BOOT_IMAGE=' -e '^initrd=' removes specific boot and initrd parameters.
• tr '\n' ' ' joins parameters back into a space-separated format.
• echo $BOOT_OPTIONS > /etc/kernel/cmdline saves the updated boot options.

---

Step 5: Removing Old Rescue Kernel Entries

To ensure a clean boot setup:

rm /boot/vmlinuz-*rescue* /boot/initramfs-*rescue*

Explanation:

• rm /boot/vmlinuz-*rescue* /boot/initramfs-*rescue* removes old rescue kernel images.

Rebuild the rescue kernel:

/usr/lib/kernel/install.d/51-dracut-rescue.install add "$(uname -r)" /boot "/boot/vmlinuz-$(uname -r)"

This regenerates a rescue kernel for the current kernel version.

Verify rescue kernel presence:

ls /boot/vmlinuz-*rescue* /boot/initramfs-*rescue*

If verification is needed:

lsinitrd /boot/initramfs-*rescue*.img | grep -qm1 "$(uname -r)/kernel/" && echo "OK" || echo "FAIL"

This checks if the current kernel is properly included in the rescue image.

---

Step 6: Confirming GRUB Boot Configuration

To review the GRUB bootloader settings:

grubby --info $(ls /boot/vmlinuz-*rescue*)

This will display boot parameters associated with the rescue kernel.

---

Step 7: Final System Reboot

Once all steps are complete, reboot the system:

reboot

This will apply the changes and boot into the upgraded RHEL 9 environment.

---

Conclusion

This document provides a structured approach to upgrading from RHEL 8 to RHEL 9, covering package removal, kernel boot parameter adjustments, and GRUB bootloader updates to ensure a smooth transition.