The content is valid only on PPC64 architecture.
The content checks if yaboot is installed on PPC64 machine.

Yaboot can not boot Red Hat Enterprise Linux 7. Redhat-upgrade-tool will install grub2 during the upgrade. It is necessary to create /etc/default/grub before running redhat-upgrade-tool to ensure correct grub2 configuration. Misconfiguration can make the system unbootable. As an example, /etc/defaults/grub can look like this:

GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
# insert storage and other kernel parameters here
GRUB_CMDLINE_LINUX="rd.lvm.lv=rhel/root crashkernel=auto  rd.lvm.lv=rhel/swap vconsole.font=latarcyrheb-sun16 vconsole.keymap=us rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
