Ubuntu Cloud Images don’t have any password for the root or ubuntu users by default, relying only on using ssh keys. It is convenient for many tenants to just having a user and a password to log in rather than only a ssh key.
This is how to set a password for the ubuntu user:
1. Download the image:
$ wget http://cloud-images.ubuntu.com/precise/current/precise-server-cloudimg-amd64-disk1.img
2. Download backdoor-image:
$ bzr branch lp:~smoser/+junk/backdoor-image
3. Set the user and password:
$ sh backdoor-image --user ubuntu --password ubuntu --password-auth ubuntu-12.04-server-cloudimg-amd64-disk1.img
Now we can deploy the image, for example in our OpenStack infrastructure, and we can ssh into it with ubuntu as user and password or we can login via the console.