Openstack Grizzily Error "FATAL: Module openvswitch_mod not found" when start openvswitch or at startup

I came across this error on Openstack Grizzily installed on Ubuntu 12.04 LTS, when I upgrade or degrade the linux kernel. So its very likely that you will get this error after running a "dist-upgrade" on your system.

The cause of this problem seem to be that when a different kernel is used, the openvswitch modules have not been built  with it.

Error:
FATAL: Module openvswitch_mod not found.
 * Inserting openvswitch module
 * not removing bridge module because bridges exist (virbr0)
invoke-rc.d: initscript openvswitch-switch, action "load-kmod" failed.

Solution:

Copy the following script to a file. Then save.

 #!/bin/bash  
   
 sudo apt-get install linux-headers-$(uname -r)  
   
 depmod  
 modprobe openvswitch  
   
 sudo apt-get remove openvswitch-switch openvswitch-datapath-dkms quantum-plugin-openvswitch-agent  
   
 sudo apt-get install openvswitch-switch openvswitch-datapath-dkms quantum-plugin-openvswitch-agent  
   
   

Then make it make the file executable.

Go to the file directory then execute following command in terminal:

sudo chmod +x filename

Finally execute the file.

./filename