After I installed my new keyboard, I discovered that pressing Ctrl+Alt+Fn keys no longer brings me to the tty screens(nothing happens), but
sudo chvt 1 in the terminal emulator can start the tty. Meanwhile, Ctrl+Alt+F7 could bring me back to the x-window.
My keyboard is i-rocks IK6 (I didn't have such problem when using my old Logitech K120 keyboard)
How should I fix this problem? My system is Ubuntu 14.04 with Kernel 3.19.0-27-generic
p.s. I'm not an English Speaker so please forgive my English and ask me for details if I failed to express clearly...