Keyboard Mapping in Linux with xmodmap

Customise Keyboard key mapping in Linux if the keyboard layout has different buttons associated with other actions. This mainly happens with the Alt, Ctrl and Super(Windows) keys.

Table of contents

TL;DR

xmodmap is a utility for modifying keymaps and pointer button mappings in X. We can easily remap the keys in a Linux-like system. For our use case, we can remap the Alt and Super(Windows) keys to the desired keys.

Temporary remapping

• Run xmodmap -pke to see the current key mappings’
• Run xmodmap -e "keycode 64 = Alt_L" to remap the key with keycode 64 to Alt_L
• Run xmodmap -e "keycode 133 = Super_L" to remap the key with keycode 133 to Super_L

Mapping with proper configuration file

• Create or update file ~/.Xmodmap with the key mappings that we want to change
• Add the following lines to the file

clear Mod1
clear Mod4
keycode 133 = Alt_L
keycode 108 = Alt_R
keycode 64 = Super_L
keycode 134 = Super_R
add Mod1 = Alt_L Alt_R
add Mod4 = Super_L Super_R

• Run xmodmap ~/.Xmodmap to apply the changes. This will apply the changes to the current session. To make the changes permanent, add the command to the startup script of the desktop environment.

Introduction

I’ve recently switched to a new keyboard and the layout of the keyboard is different than the previous one. The new keyboard has a different design for the Alt and Super(Windows) keys. The Alt key is mapped to the Super key function and vice versa. This is causing a lot of confusion while using the keyboard shortcuts. I wanted to remap the keys to the desired keys. I’ve found that xmodmap is the utility that can be used to remap the keys in a Linux-like system.

Get current key mappings

To get the current key mappings, we can use the xmodmap -pke command. This will print the current key mappings to the terminal. We can use this output to find the keycodes of the keys that we want to remap.

$ xmodmap -pke

For our use case, we want to remap the Alt and Super(Windows) keys. Execute the following command and grep the output to find the keycodes of the keys that we want to remap.

$ xmodmap -pke| egrep  -e '(Alt|Super)'
# Output
# keycode  64 = Super_L NoSymbol Super_L NoSymbol Super_L
# keycode 108 = Alt_R NoSymbol Alt_R
# keycode 133 = Alt_L NoSymbol Alt_L NoSymbol Alt_L
# keycode 134 = Super_R NoSymbol Super_R NoSymbol Super_R
# keycode 204 = NoSymbol Alt_L NoSymbol Alt_L NoSymbol Alt_L
# keycode 206 = NoSymbol Super_L NoSymbol Super_L NoSymbol Super_L

From the above output, we can see that the keycodes for the Alt and Super keys are 133 and 64 respectively. For my current keyboard layout, I want to remap the Alt key to the Super key and vice versa. So I will remap the key with keycode 133 to Super_L and the key with keycode 64 to Alt_L.

To get current modifiers, we can use the xmodmap -pm command.

$ xmodmap -pm
# Output
# xmodmap:  up to 4 keys per modifier, (keycodes in parentheses):
# shift       Shift_L (0x32),  Shift_R (0x3e)
# lock
# control     Control_L (0x25),  Control_R (0x69)
# 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)

Remap the keys

For temporary remapping of the keys, we can use the xmodmap -e command. However, this will only apply the changes to the current session. To make the changes permanent, we can create a configuration file ~/.Xmodmap and add the key mappings to this file.

Temporary remapping of the keys. This is to test the key mappings.

$ xmodmap -e "keycode 64 = Alt_L"
$ xmodmap -e "keycode 133 = Super_L"

Note: It might be possible that the Alt button does not start working as expected. This is due to the fact that the Alt key is also used as the Meta key in some of the applications. To fix this issue, we need to clear the Mod1 and Mod4 modifiers and then add the Alt and Super keys to the Mod1 and Mod4 modifiers respectively.

.Xmodmap configuration file for permanent key mappings

Once the above setup is verified and working as expected, we can add the key mappings to the ~/.Xmodmap file.

$ nano ~/.Xmodmap

Add the following lines to the file.

clear Mod1
clear Mod4
keycode 133 = Alt_L
keycode 108 = Alt_R
keycode 64 = Super_L
keycode 134 = Super_R
add Mod1 = Alt_L Alt_R
add Mod4 = Super_L Super_R

In the above configuration file, we are clearing the Mod1 and Mod4 modifiers before reassigning the keys.

Apply the changes

To apply the changes, we can run the following command.

$ xmodmap ~/.Xmodmap

This will apply the changes to the current session. To make the changes permanent, we need to add the above command to the startup script of the desktop environment.

Adding the command to the startup script

To make the changes permanent, we need to add the xmodmap ~/.Xmodmap command to the startup script of the desktop environment.

For Ubuntu, we will be using startup applications to add the command. Open the startup applications and add the command to the list of startup applications. To open the start-up applications, search for Startup Applications in the application menu. Click the Add button and add the command bash -c '[ -f "$HOME/.Xmodmap" ] && xmodmap "$HOME/.Xmodmap"' to the command field.

Once done with the above steps, restart the system and the changes should be applied.

Conclusion

In this post, we have seen how to remap the keys in a Linux-like system using the xmodmap utility. We have seen how to get the current key mappings and remap the keys temporarily and permanently. We have also seen how to add the command to the startup script of the desktop environment to make the changes permanent.