I have installed openstack juno using the following commands at the ubuntu 14.04 LTS commandline:

sudo apt-get update
sudo apt-get install git
git clone https://github.com/openstack-dev/devstack -b stable/juno
cd devstack
sudo apt-get install vim
sudo vim stackrc

in this stackrc i have changed GIT_BASE=${GIT_BASE:-https://www.github.com}

i have saved and quit stackrc. then had executed the following at the command prompt

./stack.sh

it took passwords for nova, glance,etc. finally openstack is installed with dashboard user id : admin or demo and passward and it had given me ip address also. now after logging into dash board, when i am trying to create instances i am getting a problem saying that there is an error and unable to launch instances. please help with the solution steps i need to perform to overcome the problem.