How do I enable, disable the laptop's camera from terminal? And how will I know if it is on or of?
Press Ctrl+Alt+T on your keyboard to open terminal.
When it opens, run command to disable the camera until reboot:
sudo modprobe -r uvcvideo
You will be asked for your password, and after typing it, if there are no errors shown in the terminal, your webcam should be disabled.
To enable your webcam again, run:
sudo modprobe uvcvideo