Check disk usage before backup to usb

src/freedombone

@@ -2585,7 +2585,24 @@ function create_backup_script {
   echo '  rm -rf $USB_MOUNT' >> /usr/bin/$BACKUP_SCRIPT_NAME
   echo '  exit 27' >> /usr/bin/$BACKUP_SCRIPT_NAME
   echo 'fi' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '' >> /usr/bin/$BACKUP_SCRIPT_NAME
 
+  echo -n 'used_percent=$(df -k $USB_MOUNT | ' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo -n "awk -F ' ' '{print " >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo -n '$5' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo -n "}' | " >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo -n "awk -F '%' '{print " >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo -n '$1' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo "}')" >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo 'if [ $used_percent -gt 95 ]; then' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '  ' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '  echo "Less than 5% of space remaining on backup drive"' >> /usr/bin/$BACKUP_SCRIPT_NAME 
+  echo '  umount $USB_MOUNT' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '  rm -rf $USB_MOUNT' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '  exit 6492' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo 'fi' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  echo '' >> /usr/bin/$BACKUP_SCRIPT_NAME
+  
   echo '# MariaDB password' >> /usr/bin/$BACKUP_SCRIPT_NAME
   echo -n 'DATABASE_PASSWORD=$(cat ' >> /usr/bin/$BACKUP_SCRIPT_NAME
   echo "$DATABASE_PASSWORD_FILE)" >> /usr/bin/$BACKUP_SCRIPT_NAME