How can I reboot the RHEL from CLI using the systemctl method?
As root, say
# systemctl --reboot
On systems where
systemctl can reboot the system,
reboot is usually symlinked to it, so that
systemctl detects the action to perform by the name it was called by.
If you're on RHEL 7 or newer or you have manually configured
sudo on RHEL 6 or older, you may not have to log in as
su up to
$ sudo systemctl --reboot
$ sudo reboot