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I would like to have the left and right ctrl keys to behave the same. I already have the left key working as it should, in all the shortcuts, etc., but the right one seems to be completely ineffective. I have looked in the keyboard layout options, but with no results.

I am on Linux Mint 20.2, with Mate desktop environment.

--addendum--

The result of xev is as follows:

KeyPress event, serial 35, synthetic NO, window 0x5200001, root 0x7ac, subw 0x5200002, time 416256, (49,43), root:(2600,505), state 0x10, keycode 105 (keysym 0xff20, Multi_key), same_screen YES, XLookupString gives 0 bytes: XmbLookupString gives 0 bytes: XFilterEvent returns: True KeyRelease event, serial 38, synthetic NO, window 0x5200001, root 0x7ac, subw 0x5200002, time 416464, (49,43), root:(2600,505), state 0x10, keycode 105 (keysym 0xff20, Multi_key), same_screen YES, XLookupString gives 0 bytes: XFilterEvent returns: False

The output of xmodmap is as follows:

xmodmap: up to 4 keys per modifier, (keycodes in parentheses): shift Shift_L (0x32), Shift_R (0x3e) lock Caps_Lock (0x42) control Control_L (0x25) mod1 Alt_L (0x40), Meta_L (0xcd) mod2 Num_Lock (0x4d) mod3 mod4 Super_L (0x85), Super_R (0x86), Super_L (0xce), Hyper_L (0xcf) mod5 ISO_Level3_Shift (0x5c), Mode_switch (0xcb)
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  • Can you see Control_L and Control_R respectively when you press left and right controls after running xev in the terminal? Commented Dec 31, 2021 at 11:49
  • I see "Control_L" for the left ctrl, but for the right ctrl I receive a "Multi_key". Commented Dec 31, 2021 at 14:28
  • what's the output of your xmodmap? Commented Jan 5, 2022 at 21:00
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    ok, try, first, xmodmap -e "keycode 105 = Control_R NoSymbol Control_R", then xmodmap -e "add control = Control_R". If it doesn't work, then again it would be worth to see the output of xmodmap after these commands, and xev for the right control. Commented Jan 6, 2022 at 17:50
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    Glad to hear it! By the way, you can improve your question if you add xev output showing this Multi_key and the output of xmodmap (like in the comment on Jan 6). Commented Jan 10, 2022 at 19:36

3 Answers 3

Reset to default
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As you confirm in comments, the following two xmodmap commands do the trick:
xmodmap -e "keycode 105 = Control_R NoSymbol Control_R"
xmodmap -e "add control = Control_R"

It will not stay after reboot, so you need to save only the text in quotes in ~/.Xmodmap file and make it executed at startup.

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  • could you please help with the "after restart" part, please? I have created the ~/.Xmodmap file, I have copied the two lines: keycode 105 = Control_R NoSymbol Control_R add control = Control_R then I have followed all the suggestions in this post: forums.linuxmint.com/viewtopic.php?t=294096 but with no success :( Commented Jan 11, 2022 at 11:15
  • just to see whether the file is ok: if you execute xmodmap $HOME/.Xmodmap in cmd, does the mapping work, no error messages? Commented Jan 11, 2022 at 18:20
  • I just tried, xmodmap $HOME/.Xmodmap works, with no error messages! Commented Jan 12, 2022 at 11:26
  • I did a small progress: following the suggestions in forums.linuxmint.com/viewtopic.php?t=294096 I have created ~/.xprofile, and inside I have written: bash -c "sleep 5; xmodmap $HOME/.Xmodmap" & On reboot, the right ctrl has worked, but only for few seconds... then it has gone back to the usual situation :-/ Commented Jan 12, 2022 at 14:28
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    did you also try to add the command (maybe with full path, not $HOME variable) to Startup Applications (try to increase the delay)? And I see that you created a new question - it's better to try to solve this new problem there. Commented Jan 12, 2022 at 18:00
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xmodmap -e "keycode 105 = Control_L NoSymbol Control_L"
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  • I tried this, but it doesn't work, sorry... :( Commented Jan 3, 2022 at 7:46
  • Important note for people who might want to do this on Ubuntu 20+: The default windowing system used is Wayland, in which this won't work. This solution is for X.Org windowing system. You can select the X.Org windowing system (on which this solution should work) in the login screen where you enter your password (click the small gear icon at the bottom right of the screen and select - Ubuntu on X.Org if the two options are Ubuntu and Ubuntu on X.Org - Ubuntu on Wayland if the two options are Ubuntu and Ubuntu on Wayland Commented Dec 6, 2022 at 15:25
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I have found a more stable and final solution! The behavior I want (both ctrl keys, left and right, having the same behavior) is indeed the default.

My problem was that a keyboard setting was changing this default.

I just found this setting, I have de-selected it, and the default (wanted) behavior is obtained!

The setting is reached as follows:

Keyboard preferences -> Layouts -> Options -> Position of Compose key -> Right Ctrl.

Below I report the screenshots:

first window of the Keyboard Preferences

second window for the layout options

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