Docker-machine can't use userdata add key to ssh cloud image - ssh

Question

My provider : OpenStack
VM OS: Ubuntu 16.04
Docker-machine Version: 0.14.0
Problem:
I want to use userdata add another public key to authorized_keys,
using --openstack-user-data-file option to specify my userdata.yml.
Here is my userdata.yml:
#cloud-config
users:
- default
- name: ubuntu
groups: sudo
shell: /bin/bash
sudo: ['ALL=(ALL) NOPASSWD:ALL']
ssh-authorized-keys:
- ssh-rsa XXXXXXXXXXXXXX
Use docker-machine command to create vm:
docker-machine --debug create --driver openstack
--openstack-auth-url http://x.x.x.x:5001/v3
--openstack-domain-id defaule
--openstack-endpoint-type adminURL
--openstack-floatingip-pool ext-net
--openstack-keypair-name mykey
--openstack-flavor-id 4
--openstack-image-name ubuntu-16.04-cloud
--openstack-net-name private
--openstack-password XXXXX
--openstack-private-key-file /home/demo/id_rsa
--openstack-sec-groups default
--openstack-ssh-user ubuntu
--openstack-tenant-name admin
--openstack-user-data-file /home/demo/userdata.yml
--openstack-username admin
vm
After creating vm , docker-machine stuck " waiting for ssh to be available".
Here is debug output:
Getting to WaitForSSH function...
(vm) Calling .GetSSHHostname
(vm) Calling .GetSSHPort
(vm) Calling .GetSSHKeyPath
(vm) Calling .GetSSHKeyPath
(vm) Calling .GetSSHUsername
Using SSH client type: external
Using SSH private key: /root/.docker/machine/machines/vm/id_rsa (-rw-------)
&{[-F /dev/null -o PasswordAuthentication=no -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o LogLevel=quiet -o ConnectionAttempts=3 -o ConnectTimeout=10 -o ControlMaster=no -o ControlPath=none ubuntu#10.50.2.36 -o IdentitiesOnly=yes -i /root/.docker/machine/machines/vm/id_rsa -p 22] /usr/bin/ssh <nil>}
About to run SSH command:
exit 0
SSH cmd err, output: exit status 255:
Error getting ssh command 'exit 0' : ssh command error:
command : exit 0
err : exit status 255
output :
I try to ssh to vm by command:
ssh -i /root/.docker/machine/machines/vm/id_rsa ubuntu#10.50.2.36
But got error message:
Permission denied (publickey).
So, I try another key , the key was in option of --openstack-private-key-file /home/demo/id_rsa
ssh -i /home/demo/id_rsa ubuntu#10.50.2.36
ssh was successful!
I checked two keys, /root/.docker/machine/machines/vm/id_rsa and /home/demo/id_rsa,
but two keys are the same.
I was confused, why the same keys, one can ssh another one can't ssh?

Answer 1

In order for Docker-Machine to set-up a virtual machine on OpenStack, you need to activate the config_drive option: docker-machine --openstack-config-drive [OTHER_OPTIONS] <MACHINE_NAME>