1. aptitude -y install libguestfs-tools
 

2. guestfish --rw -a ubuntu-14.04-server-cloudimg-amd64-disk1.img
><fs> run
><fs> list-filesystems
/dev/sda1: ext4
><fs> mount /dev/sda1 /

><fs> edit /etc/ssh/sshd_config

PermitRootLogin yes
 

PasswordAuthentication yes
 

><fs> exit

3. on Horizon node (normally controller node)

vi /etc/openstack-dashboard/local_settings.py

OPENSTACK_HYPERVISOR_FEATURE = {
...
'can_set_password': True,
}

service apache2 restart; service memcached restart

4. on compute nodes:

vi /etc/nova/nova.conf

[libvirt]
inject_password=true

service nova-compute restart

5. now when you launch instance, you can set root password within dashboard

6. then you can login with publickey or root