Backup existing /etc/dnsmasq.conf if present and ensure that /etc/dnsmasq.conf contains only "conf-dir=/etc/dnsmasq.d"

Signed-off-by: DL6ER <dl6er@dl6er.de>

automated install/basic-install.sh

@@ -2109,12 +2109,14 @@ FTLinstall() {
                 fi
             fi
 
-            #ensure /etc/dnsmasq.conf contains `conf-dir=/etc/dnsmasq.d`
-            confdir="conf-dir=/etc/dnsmasq.d"
-            conffile="/etc/dnsmasq.conf"
-            if ! grep -q "$confdir" "$conffile"; then
-                echo "$confdir" >> "$conffile"
-            fi
+            # Backup existing /etc/dnsmasq.conf if present and ensure that
+            # /etc/dnsmasq.conf contains only "conf-dir=/etc/dnsmasq.d"
+            local conffile="/etc/dnsmasq.conf"
+            if [[ -f "${conffile}" ]]; then
+                mv "${conffile}" "${conffile}.old"
+            fi
+            # Create /etc/dnsmasq.conf
+            echo "conf-dir=/etc/dnsmasq.d" > "${conffile}"
 
             return 0
         # Otherwise,