View source for Linux/Rename User and Home Directory

Change user name, and rename home directory:
 # -m, --move-home
 # -l, --login NEW_LOGIN
 # -d, --home HOME_DIR
 sudo usermod -m -l newuser -d /home/newuser  olduser

Fix user's default group:
 # -n, --new-name NEW_GROUP
 sudo groupmod -n newuser  olduser

 ..

Should not be needed, but just in case??
 sudo chown -R newuser:newuser /home/newuser