Sometimes happen that your desktop freeze and you cannot do anything, so the only choice is to unplug the power cord ?
No, Linux has the magic SysRq key that can sync your disk and issue a reboot of your system…and many more things.
What is the magic SysRq key?
It is a ‘magical’ key combo you can hit which the kernel will respond to
regardless of whatever else it is doing, unless it is completely locked up.