Create add-sudo.sh file with command :

su root
nano ~/add-sudo.sh

Paste this content:

#!/bin/bash
if [ $# -eq 0 ]; then
    echo "Enter Username"
    exit 1
else
  USER=$1
  sudo usermod -aG sudo ${USER}
  if [ -f /etc/sudoers ]; then
    sudo echo "File exists."
    sudo echo ${USER}'  ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
    sudo echo 'add: "' ${USER} '  ALL=(ALL) NOPASSWD:ALL" in /etc/sudoers file'
  else
    echo "File /etc/sudoers does not exist"
    exit 1
  fi
fi

Make add-sudo.sh executable:

chmod +x ~/add-sudo.sh

Usage :

su root
bash ~/add-sudo.sh nolwennig

(NOTE: Change ‘nolwennig’ for Your username)

---

Add alias and Function in ~/.bashrc or ~/.zshrc

add-sudo() {
   sudo /home/root/add-sudo.sh $1
}

Usage :

add-sudo nolwennig

(NOTE: Change ‘nolwennig’ for Your username)