There are two scripts here which I use to launch and teardown nova
They both require some small tweaks for your system
You'll need to make sure your directory structure is setup correctly
your nova code should be in a directory called nova underneath the directory n3va.sh is in
I use symlinks to swap that code in and out easily

then it's
n3va.sh run       -> runs nova in a screen session
n3va.sh clean     -> clean up the screen session and kills the running processes
n3va.sh teardown  -> wipes database, clobbers the xenserver instances

place the clobber script on your xenserver dom0 and n3va.sh will call it
or
run script manually to shutdown and uninstall all VMs on a xenserver.
If there are some VMs you would like the script to ignore add them
to the ignored array in the script (YOU WILL WANT YOUR COMPUTE INSTANCE LISTED HERE)

if you are in a bad state and wish to wipe the xenserver completely
call the script with WIPE as an argument, ex:
clobber.sh WIPE