How many compute nodes do you have? It's trying to copy over the data to another server. You can move around SSH keys and allow the nodes to connect to each other, or if you have 1 node as a compute you just need to modify the "allow_resize_to_same_host" option in nova.conf:

http://docs.openstack.org/juno/config...

allow_resize_to_same_host = False   (BoolOpt) Allow destination machine to match source for resize. Useful when testing in single-host environments.

Change this to True, restart nova services, attempt to resize again. If you are resizing down to a smaller flavor then you'll probably run into errors again when the disk size is smaller than the original size.

If you have multiple compute nodes then you can look into setting up migrations, which should help with this issue:

http://docs.openstack.org/admin-guide...

make sure your nova user has appropriate shell set, if not run:

usermod -s /bin/bash nova

Now generate SSH keys using "nova" users.

su - nova ssh-keygen -t rsa

Save the key without a passphrase.

Next up we need to configure SSH to not do host key verification, unless you want to manually SSH to all compute nodes that exist and accept the key

cat << EOF > ~/.ssh/config
Host *
    StrictHostKeyChecking no
    UserKnownHostsFile=/dev/null
EOF

Next we need to make sure we copy the the contents of id_rsa.pub to authorized_keys and set the mode on it correctly

cat ~/.ssh/id_rsa.pub > .ssh/authorized_keys
chmod 600 .ssh/authorized_keys

Now comes the important part, you will need to tar up and copy the ~nova/.ssh directory to every single compute node you have provisioned. This way all compute nodes will be able to SSH to the remote host to run the commands required to copy an instance over, and resize it.