test if running as root

Scripts/gadget.sh

@@ -3,20 +3,31 @@
 # "Using OTG mode on Raspberry Pi SBCs"
 # https://pip-assets.raspberrypi.com/categories/685-app-notes-guides-whitepapers/documents/RP-009276-WP/Using-OTG-mode-on-Raspberry-Pi-SBCs
 
-# Is the dwc2 overlay installed?  Nothing will work if it isn't.
-LOGGER="systemd-cat -t gadget.sh"
-if lsmod | grep -q "dwc2"; then
-    $LOGGER -p info "DWC2 module loaded, setting up OTG gadget serial and ethernet"
-else
-    $LOGGER -p warning "DWC2 module missing.  Aborting OTG setup"
+# This script only works if you are running it as root
+if [ $(id -u) -ne 0 ]; then
+    echo "Please run as root or use sudo"
     exit 1
 fi
 
 
+# Is the dwc2 overlay installed?  Nothing will work if it isn't.
+if lsmod | grep -q "dwc2"; then
+    systemd-cat -t gadget.sh -p info echo "DWC2 module loaded, setting up OTG gadget serial and ethernet"
+else
+    systemd-cat -t gadget.sh -p warning echo "DWC2 module missing.  Aborting OTG setup."
+    systemctl disable serial-getty@ttyGS0.service
+    exit 1
+fi
+
 sudo modprobe libcomposite
 cd /sys/kernel/config/usb_gadget
+if [ -d "MyGadget" ]; then
+    systemd-cat -t gadget.sh -p warning echo "MyGadget already exists.  Aborting OTG setup."
+    exit 1
+fi
+
 # Create our new gadget
-sudo mkdir MyGadget
+mkdir MyGadget
 cd MyGadget
 # Add some boilerplate data that the gadget needs
 echo 0x1d6b > idVendor # Linux Foundation’s USB VID. Replace with your own VID if required
@@ -41,6 +52,7 @@ echo "Config 1" > configs/c.1/strings/0x409/configuration
 ###  Remember to create the storage block device first
 ##  cd /root
 ### Example: Make a 256 MB file to act as "USB stick"
+##  Only create it once or it will delete the previous content
 ##  sudo dd if=/dev/zero of=drive.bin bs=1M count=256
 ### Create a VFAT file system on the backing store
 ##  sudo mkfs.vfat drive.bin
@@ -64,3 +76,6 @@ ln -s functions/ecm.usb0 configs/c.1/
 ## USB Device Controller update
 UDC=`ls /sys/class/udc`
 echo $UDC > UDC
+
+# Enable the gettys
+systemctl enable serial-getty@ttyGS0.service