I had the same error and resolved executing the following steps:

generate the public private keys

ssh-keygen -t dsa -P '' -f ~/.ssh/id_dsa

copy the public key to every host you will connect TO:

scp ~/.ssh/id_dsa.pub my_user_id@1.2.3.4:~/.ssh/id_dsa.pub

(this should prompt you for a password)

shell into the remote machine

ssh my_user_id@1.2.3.4

authorize the key by adding it to the list of authorized keys

cat ~/.ssh/id_dsa.pub >> ~/.ssh/authorized_keys

log out of the current shell

exit

test that you can log in with no password

ssh -i ~/.ssh/id_dsa 1.2.3.4

if this prompts for a password ensure the remote user is the owner of the pub key http://hortonworks.com/kb/generating-ssh-keys-for-passwordless-login/ ((source))

This is from compute1 to compute2 nodes and from controller to compute2 node. Also, I had to allow nova user permissions to write:

If you want to change the user owning this file or directory (folder), you will have to use the command chown. For instance, if you run

`sudo chown username: myfolder`

the user owning myfolder will be username. Then you can execute

`sudo chmod u+w myfolder`

to add the write permission to the username user.

But if you want to add this user to the group associated with "myfolder", you can run

`sudo usermod -a -G groupname username`

and then execute

`sudo chmod g+w myfolder`

to add the write permission to the group.

http://askubuntu.com/questions/487527/give-specific-user-permission-to-write-to-a-folder-using-w-notation ((source))