How do I remap certain keys or devices?

Question

I'm searching for a way to remap certain keys in ubuntu.

i.e.

I'd like to change PgUp to Home or PgDown to End.

Does a built-in command or a tool exist reassign keys in Ubuntu/GNOME?

Answer 1

Notice: As of 2013, Ubuntu and derivatives no longer use xmodmap, but instead use xkb. For more information see this answer. The answer below is no longer relevant for current releases.

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For remapping certain keys you need two tools. First xev (command-line tool) and second xmodmap (also command-line tool). Both should be available in Ubuntu without extra installing them.

1. Start terminal window and run xev. Now it's active and waits for you to press a key. Then press the key whose behaviour you want to change. i.e. PgUp.

2. xev will output some information about the pressed key. The third line is important. It should look similar to:

   state 0x10, keycode 110 (keysym 0xff55, Prior), same_screen YES,
   

   in this example Prior is the name of the behaviour the key is assigned to at the moment, the number keycode is the internal id to recognize the key. Now do this with another key i.e. PgDown give this output

   state 0x10, keycode 115 (keysym 0xff56, Next), same_screen YES,
   

   Here again the interesting part for us is keycode 115 and Next - the name of the behaviour.

3. now when you want to swap the two keys use xmodmap.

    xmodmap -e "keycode 110 = Next"
   

   This changes the key with keycode 110 on your keyboard to the action Next. It's pretty simple.

   Note that if the key you are mapping should have a different meaning when used with the Shift key (for example for British keyboard layouts, Shift+2 gives quotation marks) then you can simply list the secondary command after the first. For example if you want the key with code 53 to map to backslash normally, but to the bar symbol when used with shift, you might do:

    xmodmap -e "keycode 53 = backslash bar"
   

Additional information: The sequence of these mappings is Key, Shift+Key, mode_switch+Key, mode_switch+Shift+Key, AltGr+Key, AltGr+Shift+Key. To skip a column use NoSymbol. Moreover, here is a comprehensive list of all keysyms.

Note: These change are for the active X session only and will be lost after reboot. When you want to save the changes permanently you have to run the following commands after the ones above:

xmodmap -pke >~/.Xmodmap

(it creates a file named .Xmodmap in your home directory (~))

Then you have to create a file named .xinitrc in your home directory where you put command xmodmap .Xmodmap in.

You can now modify .Xmodmap and run xmodmap .Xmodmap from console to see the changes immediately. The changes in .Xmodmap will persist.

source: Ubuntu Foruns

Bonus stuff:

If the key you are remapping has different behavior depending on a state ( like how the keys in the numeric keyboard depend on NumLock) you simply have to do xmodmap -pm to get a list of modifiers and then do:

xmodmap -e "KEYCODE MODIFIER = behaviour behaviour_with_modifier"

Suppose, for example, that you want to get a period instead of a comma on the numeric keyboard (useful for most programmers), but you want to keep the "delete" behavior when NumLock is off.

xmodmap -e "keycode 91 mod2 = KP_Delete period"

mod2, because xmodmap -pm tells us that mod2 is Num_Lock, the other names are obtained by pressing the keys in xev.

Answer 2

I've just had an afterthought.. I think you may mean something entirely different by "remap".. but I'll leave my answer as it is... (I don't know how to re-assign one key to behave as another)

UPDATE: my 'afterthought' has been confirmed; ( I've answered the wrong question :)... please see NES's Community Wiki answer (accepted above).

There are two general ways to remap rebind a key.

• locally to a particular program
  (a key can be used for different things in different apps/windows)
• globally for a specific user
  (a key has the same function in all windows)

For 'local to a program' methods, there is sometimes a way to change keybindings offered by the app itself... eg.

Firefox has an addon called keyconfig ... for some info see this MozillZine post

Most Ubuntu programs are Gnome based and there is a specific utility to modify the keybinding for any menu item of these Gnome apps... It is called Editable Menu Accelerator ... It is a very 'touchy' tool, but quite powerful.. You can enable it by running gconf-editor (via Terminal or Alt+F2)... navigate to desktop--gnome--interface and select can_change_accels .... You can then change menu items to virtual anything you like (per program/window)... I suggest you disable it as soon as you've done what you need..

Otherwise you can set up Global hotkeys. I use a program called xbindkeys , and there is also an option available via the Main Menu -- Preferences, called Keyboard Shortcuts

If you use xbindkeys, you will need to add it to your "Startup Applications" (Main Menu -- Preferences) ... Also (as suggested by Stefano Palazzo) I have previously written a more detailed description of xbindkeys in an answer on this askubuntu page

Answer 3

I spent one whole day in trying to create a shortcut for Ctrl+Pageup.

I first tried xmodmap but that can't generate modifier events. So it is impossible to create a shortcut that generates for example the Control event.

I then tried xbindkeys with xmacro. That sort of works, but xbindkeys is not able to capture some key combinations on my system, such as Alt + ___.

So I finally used Unity's own Keyboard Shortcuts -> Custom Shortcuts to setup my shortcut.

And instead of xmacro, I have now used xvkbd program to generate the keyboard events, but that is just a personal preference. Both xmacro and xvkbd work almost the same. One additional tip is to add a delay parameter in xmacro or xvkbd to ensure that the events don't get lost.

Answer 4

In order to do global remaps independently of X, you can make use of console-setup(5) instead.

In my case I wanted to remap Caps Lock key to D, since my D-key is broken :)

First I used dumpkeys(1) to get a template for a mapping, in the case of the D-key, the interesting bit is the mapping for keycode 32 (on my keyboard); Note that there are two spaces in the grep pattern!

$ sudo dumpkeys | grep "keycode  32" > tempfile
$ cat tempfile
keycode  32 = +d
    shift   keycode  32 = +D
    altgr   keycode  32 = +eth
    shift   altgr   keycode  32 = +ETH
    control keycode  32 = Control_d
    shift   control keycode  32 = Control_d
    altgr   control keycode  32 = Control_d
    shift   altgr   control keycode  32 = Control_d
(121 lines total...)

In order to change the map to apply to Caps Lock (keycode 58 on my keyboard) instead

sed 's/32/58/' -i tempfile

Now it reads

keycode  58 = +d
    shift   keycode  58 = +D
    altgr   keycode  58 = +eth
(etc...)

To add this remap to the default map, it simply needs to be appended to the remap include file for console-setup

sudo sh -c 'cat tempfile >> /etc/console-setup/remap.inc'

and console-setup needs to be reconfigured (skipping low priority questions with -phigh)

sudo dpkg-reconfigure console-setup -phigh

Now the remap should be completed, and be loaded automatically on boot.

Answer 5

If you're trying to move a Shift key, there are a few extra steps:

 xmodmap -e "keycode 62 = Up" # Shift => Up
 xmodmap -e "keycode 111 = Shift_R" # Up => Shift
 xmodmap -e "add shift = Shift_R" # Make the new Shift key actually do shifting
 xmodmap -e "remove shift = Up" # Prevent the old Shift key from shifting
 xset r 62 # Make the new Up key autorepeat
 xset -r 111 # Prevent the new Shift key from autorepeating

Answer 6

Here is how I tried to switch the mapping of the ENTER key to the SHIFT key (and vice versa):

$ uname -a

REPORTS:

Linux box 2.6.32-37-generic #81-Ubuntu SMP Fri Dec 2 20:35:14 UTC 2011 i686 GNU/Linux

$ which xmodmap

REPORTS:

/usr/bin/xmodmap

$ which xev

REPORTS:

/usr/bin/xev

$ xev

(ignore the next fifty lines or so)

PRESS THE ENTER KEY (notice the third line):
KeyPress event, serial 33, synthetic NO, window 0x5600001,
    root 0x110, subw 0x0, time 263441120, (738,242), root:(771,314),
    state 0x0, keycode 36 (keysym 0xff0d, Return), same_screen YES,
    XLookupString gives 1 bytes: (0d)
    XmbLookupString gives 1 bytes: (0d)
    XFilterEvent returns: False

KeyRelease event, serial 33, synthetic NO, window 0x5600001,
    root 0x110, subw 0x0, time 263441271, (738,242), root:(771,314),
    state 0x0, keycode 36 (keysym 0xff0d, Return), same_screen YES,
    XLookupString gives 1 bytes: (0d)
    XFilterEvent returns: False

PRESS THE SHIFT KEY (notice the third line):
KeyPress event, serial 30, synthetic NO, window 0x5600001,
    root 0x110, subw 0x0, time 263592202, (464,368), root:(497,440),
    state 0x0, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 33, synthetic NO, window 0x5600001,
    root 0x110, subw 0x0, time 263592298, (464,368), root:(497,440),
    state 0x1, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

What's important is the third line of each keypress:

FOR:
state 0x0, keycode 36 (keysym 0xff0d, Return), same_screen YES,
The name "Return" is the name of the behavior of the key pressed.
The number of the key pressed is "36".

state 0x0, keycode 62 (keysym 0xffe2, Shift_R), same_screen YES,
The name "Shift_R" is the name of the behavior of the key pressed.
The number of the key pressed is "62".

REVERSE THE MAPPING:

$ xmodmap -e "keycode 62 = Return"
$ xmodmap -e "keycode 36 = Shift_R"

SAVE THE RESULTS:

$ xmodmap -pke > ~/.Xmodmap
$ vi ~/.xinitrc

ADD

 xmodmap ~/.Xmodmap

$ sudo reboot

The main problem was that the reversal did NOT work. The ENTER key was mapped to the SHIFT_R key; but the SHIFT_R key was not mapped to the ENTER key. Go figure.