The commands below will remove the settings from the Ethernet and Wi-Fi interfaces. You can lookup more features using the man command for networksetup. IE.. man networksetup
networksetup -setsearchdomains "Wi-Fi" "Empty"
networksetup -setdnsservers "Wi-Fi" "Empty"networksetup -setdnsservers "Ethernet" "Empty"networksetup -setsearchdomains "Ethernet" "Empty"