Ctrl-Alt-F1 not working from X

Question

I have a system running Debian 5.0 that doesn't respond to Ctrl+Alt+F# (1-6)

Check if Ctrl, Alt, F1 and F2 are intercepted correctly...

$ DISPLAY=:0 xwininfo

xwininfo: Please select the window about which you
          would like information by clicking the
          mouse in that window.

xwininfo: Window id: 0xe00002 (has no name)
...

$ xev -display :0 -id 0xe00002
KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 64 (keysym 0xffe9, Alt_L), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 67 (keysym 0xffbe, F1), same_screen YES,

KeyPress event, serial 16, synthetic NO, window 0xe00002,
    state 0x10, keycode 68 (keysym 0xffbf, F2), same_screen YES,

..They are.

However, xev does not report Ctrl+Alt+F1 as one single event. Does that mean, X does not correctly interpret that sequence?

Check if X is configured to ignore Ctrl+Alt+F#..

$ grep -i dontvtswitch /etc/X11/xorg.conf

..It isn't

But killing X with Ctrl+Alt+Backspace allows me to switch ttys.

The Xorg.0.log at pastebin.

How enable tty switching when running X?

The root filesystem is mounted as read-only. Can that affect how X setups up keyboard mappings? Tried mounting as read-write but the problem persists. Haven't been able to make the system boot up in read-write (I've set the boot options in the bootloader but something happens during boot that remounts the rootfs as readonly).

Solution

Had the same with Microsoft Natural Keyboard 4000. The answer was surprisingly simple. This keyboard had, either by default or my sloppiness, F-Lock enabled. The key presses of F1-F12 were treated as 'Help', 'Undo', 'Redo', 'New' (and so on) actions. Pressing F-Lock (right to F12 key) deactivated function lock, restoring original function keys assignments.

Comments

[Daniel Näslund]

@don_crissti: I've updated my question. Ctrl-Alt-F1 is not reported as one Keypress event, but as three. Do you know where I can find more info on how the X keyboard mapping is handled?

[vonbrand]

Got this fixed, I presume? Care to share the solution in form of an answer to your own question?

[clerksx]

I've seen this happen with some keyboards that emulate multiple input devices to achieve n-key rollover. Since the keys are not received from the same device, it does not switch VC.