• method1 : add below into /etc/default/keyboard

XKBOPTIONS="caps:escape"

and reload

sudo dpkg-reconfigure keyboard-configuration

• method2

setxkbmap -option caps:escape

and if you need to reset all option

setxkbmap -option

• method 2 --> preserve : append to ~/.xprofile
  
  
  
  

How to make CapsLock do Escape Key on Linux?

Create a file at ~/.Xmodmap with the following content:

! -*- coding: utf-8 -*-
! 2014-09-10
! make caps lock do escape
! from http://xahlee.info/

! keycode   9 = Escape NoSymbol Escape
! keycode  66 = Caps_Lock NoSymbol Caps_Lock

clear Lock
keycode 66 = Escape NoSymbol Escape
Now, run this line in terminal:

xmodmap ~/.Xmodmap

When you restart, that file will run automatically.