diff --git a/circlean_fs/root_partition/etc/udev/rules.d/10-usb.rules b/circlean_fs/root_partition/etc/udev/rules.d/10-usb.rules
index bbe5128..5480269 100644
--- a/circlean_fs/root_partition/etc/udev/rules.d/10-usb.rules
+++ b/circlean_fs/root_partition/etc/udev/rules.d/10-usb.rules
@@ -1,3 +1,3 @@
 # The purpose of this rules file is to ensure that the top left usb port and its partitions have a symlink to /dev/source_key[num], and the other ports to /dev/dest_key[num]
-KERNEL=="sd*", KERNELS=="1-1.2", SUBSYSTEMS=="usb", SYMLINK+="source_key%n"
-KERNEL=="sd*", KERNELS=="1-1.[3-5]", SUBSYSTEMS=="usb", SYMLINK+="dest_key%n"
+KERNEL=="sd*", KERNELS=="1-1.[1-5]", SUBSYSTEMS=="usb", PROGRAM="/usr/local/bin/identifyusbport.sh %p %k add", SYMLINK+="%c%n" 
+ACTION=="remove", KERNELS=="1-1.[1-5]", SUBSYSTEMS=="usb", PROGRAM="/usr/local/bin/identifyusbport.sh %p %k remove" 
diff --git a/circlean_fs/root_partition/usr/local/bin/identifyusbport.sh b/circlean_fs/root_partition/usr/local/bin/identifyusbport.sh
new file mode 100644
index 0000000..18fbefe
--- /dev/null
+++ b/circlean_fs/root_partition/usr/local/bin/identifyusbport.sh
@@ -0,0 +1,56 @@
+#!/bin/bash
+
+DEBUG_FILE=/dev/shm/identifyusbport.txt
+ACTION="connected"
+DEVPATH="$1"
+USBPORT="$2"
+
+function FoundSource(){
+		echo "upper left connected, source_key '${USBPORT}' ${ACTION}" >> ${DEBUG_FILE}
+		echo source_key
+}
+
+echo -e "\nStart" >> ${DEBUG_FILE}
+echo "Parameter 1: $1" >> ${DEBUG_FILE}
+echo "Parameter 2: $2" >> ${DEBUG_FILE}
+echo "Parameter 3: $3" >> ${DEBUG_FILE}
+
+if (echo "$3" | grep -q "remove") ; then                         
+	if (echo "$2" | grep -v -q "1-1.") ; then
+		echo "ignore unknown remove $2" >> ${DEBUG_FILE}
+		exit 0
+	fi
+	if (echo "$2" | grep -q ":") ; then
+		echo "ignore remove subpath $2" >> ${DEBUG_FILE}
+		exit 0
+	fi
+  ACTION="disconnected"
+	DEVPATH="${2}/"
+fi
+
+MODEL=$(cat /proc/device-tree/model | tr -d '\000')
+echo Device model: ${MODEL} >> ${DEBUG_FILE}
+echo Devpath: ${DEVPATH} >> ${DEBUG_FILE}
+
+if (echo "$MODEL" | grep -q "Raspberry Pi 3 Model B Plus") ; then 
+	echo "found Raspberry Pi 3 B+ with special assignment" >> ${DEBUG_FILE}
+	if (echo "${DEVPATH}" | grep -q "1-1.1.2/") ; then	
+		FoundSource	
+		exit 0
+	fi
+elif (echo "$MODEL" | grep -q "Raspberry Pi 4 Model B") ; then
+        echo "found  Raspberry Pi 4 B with special assignment" >> ${DEBUG_FILE}
+        if (echo "${DEVPATH}" | grep -q "1-1.3/") ; then                   
+                FoundSource	
+                exit 0
+        fi
+else
+        echo "unsing default mapping" >> ${DEBUG_FILE}
+        if (echo "${DEVPATH}" | egrep -q "1-1.1/|1-1.2/") ; then        
+                FoundSource
+                exit 0
+        fi
+fi
+echo "dest_key $2 $ACTION" >> ${DEBUG_FILE}
+echo dest_key
+