General workflow

For example, on a standard Cherry 104-key mechanical keyboard, the right Ctrl key is too faraway to reach. While the right Win key is relative easy to reach by the right little finger. Now we make the right Win act as a Ctrl key interactively:

Get the key name with xev. Press the right Win key in the xev window, and from the output we know its name is Super_R;
List current keymap with xmodmap -pm: xmodmap -pm xmodmap: up to 4 keys per modifier, (keycodes in parentheses): shift Shift_L (0x32), Shift_R (0x3e) lock Caps_Lock (0x9) control Control_L (0x25), Control_R (0x69) mod1 Alt_L (0x40), Alt_R (0x6c), 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) So the current group of Super_R is mod4;
Detach the right Win from current group: xmodmap -e 'remove mod4 = Super_R';
Run xmodmap -pm again and Super_R disappeared from group mod4;
Add right Win to the control group: xmodmap -e 'add control = Super_R';
Run xmodmap -pm again and the Super_R does be added to group control;
To verify, start a vim and press right Win and z, you can see the vim window is put into background, which means the map works;
To persist this behavior, add xmodmap -e 'remove mod4 = Super_R' xmodmap -e 'add control = Super_R' into ~/.xinitrc (for i3sm) or ~/.profile for graphical DE.

Swap Ctrl and Win key

Add the following lines into ~/.xinitrc:

setxkbmap -option caps:swapescape -option ctrl:swap_lwin_lctl -option ctrl:swap_rwin_rctl

Swap Caps lock and Escape Key

Swap only once

Write the following text into file ~/.swapCapsESC:

remove Lock = Caps_Lock 
keysym Escape = Caps_Lock 
keysym Caps_Lock = Escape 
add Lock = Caps_Lock

Run xmodmap ~/.swapCapsESC.

Ref: http://vim.wikia.com/wiki/Map_caps_lock_to_escape_in_XWindows

Swap permanently on Ubuntu 14.04

Option 1

Add setxkbmap -option caps:swapescape into ~/.profile (verified on Ubuntu 14.04, Unity desktop, 2016.11.27), or ~/.xinitrc (verified on Ubuntu 16.04, i3wm, 2018.11.26).

Ref: http://askubuntu.com/questions/363346/how-to-permanently-switch-caps-lock-and-esc.

Option 2

When a external keyboard is attach with USB, it may not swap these keys. Now you need run source ~/.profile again (with this keyboard).

Install dconf-editor with sudo apt-get install dconf-tools, start it with dconf-editor. In [org -> gnome >> desktop -> input-sources -> xkb-options], modify its value to ['caps:swapescape'].

Option 3

Add XKBOPTIONS="caps:swapescape" into /etc/default/keyboard.

Ref: http://askubuntu.com/questions/444714/how-do-i-swap-escape-and-caps-lock-in-14-04

Option 4

Add "only once" solution to autostart: Create file $HOME/.config/autostart/swapCapsESC.desktop:

[Desktop Entry]
Name=SwapCapsESC
Comment=Swap Caps Lock Key and ESC Key
Exec=xmodmap /home/leo/.swapCapsEsc
Type=Application
Terminal=true
X-GNOME-Autostart-Delay=5

You can also use the GUI equivalent: Run Startup Applications (input startup in dash (press Win key), add above command in it.

Swap permanently on Windows

For Windows, install AutoHotkey, save the following codes as swapCapsESC.ahk:

Capslock::Esc
ESC::Capslock

Execute it when you want to swap the keys. If you want execute it automatically when system startup, put the file in [Start -> Startup] folder (open it with inputing "shell:startup" in Run). Verified in Windows 7 & 10.

Swap Ctrl and Alt Key

remove mod1 = Alt_L Alt_R 
remove control = Control_L Control_R 
keycode 64 = Control_L 
keycode 37 = Alt_L 
keycode 108 = Control_R 
keycode 105 = Alt_R 
add control = Control_L Control_R 
add mod1 = Alt_L Alt_R

64, 37, etc are determined by "xev" command, see below for usage.

Reset Key Map to Initial State

setxkbmap -layout us

Define key swap shortcuts

It's mainly for emacs operation convenience to swap Ctrl and Alt key, and vi operation convenience to swap Caps Lock and Escape key. When you are not in emacs and vi, swap keys always lead confusions. So it's necessary to switch key definition quickly. The following are some basic method to achieve key swap shortcuts

Create a file named "swapCapsEsc" in /home/lichao/docs/swapkeys

remove Lock = Caps_Lock keysym Escape = Caps_Lock keysym Caps_Lock = Escape add Lock = Caps_Lock

and a file named "swapCtrlAlt" in /home/lichao/docs/swapkeys:

remove mod1 = Alt_L Alt_R 
remove control = Control_L Control_R 
keycode 64 = Control_L 
keycode 37 = Alt_L 
keycode 108 = Control_R 
keycode 105 = Alt_R 
add control = Control_L Control_R 
add mod1 = Alt_L Alt_R

Create keyboard shortcuts in "Application Finder (Alt + F3) -> Preferences -> Custom Actions":

Type: Regular Expression; Pattern: swce; Command: xmodmap /home/lichao/docs/swapkeys/swapCapsEsc Type: Regular Expression; Pattern: swca; Command: xmodmap /home/lichao/docs/swapkeys/swapCtrlAlt Type: Regular Expression; Pattern: swres; Command: setxkbmap -layout us

Now you can use [Alt-F2 swce] to swap Caps lock and escape key, use [Alt-F2 swca] to swap Ctrl and Alt key, use [Alt-F2 swres] to make all keys to their original state (If you have swaped ctrl and alt key, the shortcut is [Ctrl-F2 swres]).

Usage of xev

Run "xev" in command line. A little window appear. Make it active window and press some key, the keycode will show in the window.

Usage of xmodmap

Run "xmodmap -pm" we got:

shift Shift_L (0x32), Shift_R (0x3e) lock Caps_Lock (0x42) control Control_L (0x25), Control_R (0x69) mod1 Alt_L (0x40), Alt_R (0x6c), 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)

Here the names in the left column (shift, lock, control, etc) are called "Modifier Name", while the names in the right column (Shift_L, Caps_Lock, Control_R, Meta_L, etc) are called keysym. Shift_L means left shift key, while Shift_R means right shift key. Every physical key (on keyboard) has a identity (integer number) called keycode. You can use "xmodmap -pk" to investigate these relationships. And use xmodmap -e "keycode <to_be_modified> = <target_key>" to modify these relationships. For example, the following command make F2 key print "m" in gedit panel:

xmodmap -e "keycode 68 = m":

Before command:

58 0x006d (m) 68 0xffbf (F2)

(get by "xmodmap -pk"). After command:

58 0x006d (m) 68 0x006d (m)

Use xmodmap -e "keycode 68 = F2" to modify F2 back to F2 key.

The right hand side of this assignment is keysym name. So

xmodmap -e "keycode 16 = 7"

will map character "7" to physical key which has keycode 16.

"clear " means all keysyms will be detached from this . So after xmodmap -e "clear control", all control keys (left and right) are disabled.

"remove = " means remove from the list of current keysym list of the . So after xmodmap -e "remove Control = Control_R" makes right control key be disabled. When you run xmodmap -e "add Control = Control_R", the right control key is enabled again. You can use "xmodmap -pm" to verify.

"keysym name1=name2" means binding the keys (previous binded to name2) to name1;

Auto load xmodmap files when system start

xmodmap ~/.Xmodmap

Ref: http://earthviaradio.wordpress.com/2012/02/06/swapping-the-left-alt-and-ctrl-keys-in-ubuntu-11-10/

Define Keymap on Ubuntu and Windows