Document link:

https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/managing_storage_devices/managing-raid_managing-storage-devices#converting-a-root-disk-to-raid1-after-installation_managing-raid

Section number and name:

18.16. Converting a root disk to RAID1 after installation

Describe the issue:

The current documentation  suggests executing grub2-install on the whole disk . The documentation should be corrected to specify the PReP Boot Partition as the target for the grub2-install command on PowerPC architectures.

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Note
Executing the grub2-install /dev/sda command does not work on a PowerPC machine and returns an error, but the system boots as expected.

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Also the currently referenced KCS article is specific to RHEL 7. There is another kcs specifically available for RHEL9. https://access.redhat.com/solutions/7055575 

Impact of this issue:

System may not boot up correctly if grub2-install execute against whole disk.

Suggestions for improvement:

Replace the current kcs (2390831) with the equivalent RHEL 9 article: https://access.redhat.com/solutions/7055575

Also update below note:

~~~
Note
Executing the grub2-install /dev/sda1 command does not work on a PowerPC machine and returns an error, but the system boots as expected.

~~~