how to rename the username in ubuntu window manager code example

Example 1: ubuntu rename user login

#As root / or as another user. 
# Kill the processes of the user to rename
pkill -u <OldLoginName>

#Rename user login
usermod -l <OldLoginName> <NewLoginName>

#Rename HomeDir 

sudo usermod -d /home/NewHomeDir -m NewLoginName

Example 2: change ubuntu username

# To manage every aspect of the user database, you use the usermod tool.
# To change username (it is probably best to do this without being logged in):

sudo usermod -l newUsername oldUsername
# This however, doesn't rename the home folder.
# To change home-folder, use

sudo usermod -d /home/newHomeDir -m newUsername