To make a fast reboot the default behavior on your system, create a fastreboot file in the /etc directory.
# touch /etc/fastreboot
The addition of the fastreboot file on the system changes the default behavior of the reboot command, thereby eliminating the need to use the -f option to initiate a fast reboot.
To revert to the original behavior of the reboot command, remove the file.
# rm /etc/fastreboot
Note that removing this file does not remove fast reboot capability from the system.