change the DNS setting of your linux system

linux_change_dns.sh

#!/bin/sh
LOC="/etc/resolvconf/resolv.conf.d/head"

if   [[ $1 = "remove" ]]; then
    echo "nameserver 1.1.1.1" | sudo tee $LOC

elif [[ $1 = "begzar" ]]; then # begzar.ir
    echo "nameserver 185.55.226.26"  | sudo tee $LOC
    echo "nameserver 185.55.225.25"  | sudo tee -a $LOC

elif [[ $1 = "shecan" ]]; then # shecan.ir
    echo "nameserver 178.22.122.100" | sudo tee $LOC
    echo "nameserver 185.51.200.2"   | sudo tee -a $LOC
else
    echo "options: remove, begzar, shecan"
    exit
fi

sudo resolvconf -u