modtify May not run correctly place

The emergence of the following result according to the book's step operation make run
vagrant@lucid32:/vagrant$ make run 
Running Dev Operating System.
cd ./sdk && sudo ./diskimage.sh
sudo: ./diskimage.sh: command not found
make: *** [run] Error 1
so I add bash in the front of ./diskimage.sh Because when creating diskimage may forget to add execute permissions