1. Determine the current runlevel the system is configured to boot to

# systemctl get-default


The same as runlevel 3 in CentOS 6

The same as runlevel 5 in CentOS 6


2. Change default runlevel permanently

Boots CLI as default
# systemctl set-default multi-user.target 

Boots GUI as default
# systemctl set-default graphical.target 


3. Activate a run level without rebooting

Start the GUI
# systemctl isolate graphical.target

Start the CLI
# systemctl isolate multi-user.target