Virtual terminals not working? Check your keyboard.

(This is a boring post that I’m writing for people that have this same problem in the future. Just skip it.)

Every good Linux user knows that if you want to drop from X down into a text-based virtual terminal, you can press control-alt-F1 (or any other key up to F6), and control-alt-F7 returns you to the graphical mode. But what if that doesn’t work? In my case, it turned out to be my keyboard. My Microsoft Natural Ergonomic Keyboard 4000 has a key marked “F Lock” and unless that FLock key is activated (the “F” LED should be on), the wrong keystrokes were being sent to my Linux Ubuntu version of Intrepid Ibex. How can you debug this? Well, it took me a while.

After some Googling, here’s how I’d write the flowchart:

- Try running “chvt 1″ to switch your console to virtual terminal 1.
- If “chvt 1″ does not work, you might get the message “Couldnt get a file descriptor referring to the console”. You probably need to be superroot. Once you run as root, that command should work.
- Maybe “chvt 1″ fails in some other way. Dude, you’re outside my area of expertise. You could try typing “sudo modprobe vga16fb; sudo modprobe fbcon” . Or you could try typing the command “setupcon” to set up the font and keyboard on the Linux console. Or it’s possible that you need to edit /boot/grub/menu.lst and tweak the vga= setting or remove the “splash” parameter. Or you might want to check your /etc/gdm/gdm.conf file.

- Quick check: you might have the “DontVTSwitch” option set in your /etc/X11/xorg.conf file, which would disable virtual terminal switching.

- If running “chvt 1″ as superroot does work, then you probably have an issue with your keyboard mappings somehow.
- If you have a Microsoft Natural Ergonomic Keyboard 4000, make sure that the “F-Lock” key near the top-right of the main part of the keyboard is properly engaged. The “F” LED below the keyboard should be on.
- Next, run xev (possibly as root) to see raw xevents as you press keys. This thread helped, where the person said

Recently I tried to switch to VT (console) and I couldn’t – Ctrl+Alt+F1 didn’t work (and they used to couple of weeks ago). I don’t even know where to look for the problem; xev detects KeyRelease XF86_Switch_VT_1 event, /etc/inittab contain getty respawns.

When I ran xev myself, and pressed control-alt-F1, I saw an event like

KeyPress event, serial 38, synthetic NO, window 0×3400001,
root 0x1a6, subw 0×3400002, time 1848943, (42,37), root:(1751,59),
state 0×0, keycode 146 (keysym 0xff6a, Help), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False

The fact that I saw a “Help” event rather than “XF86_Switch_VT_1″ was what made me suspicious. Sure enough, activating the “F-Lock” key then triggered this event:

KeyRelease event, serial 34, synthetic NO, window 0×3400001,
root 0x1a6, subw 0×3400002, time 2873229, (38,51), root:(1747,73),
state 0xc, keycode 67 (keysym 0x1008fe01, XF86_Switch_VT_1), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False

and life was good. You might also consider tweaking xmodmap to return the values you expect. Or you might have a strange XkbModel or XkbLayout setting where switching your keyboard language or layout (e.g. from pc105 to pc104) might help.

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