Enable Live migration on compute nodes¶

First of all we need to set both enable-live-migration AND enable-resize in nova-compute configuration, otherwise Juju won’t create the SSH key pair for user nova (we opened a ticket to Canonical for this bug):
```
juju config nova-compute enable-live-migration=true enable-resize=true
```
On the compute nodes check that the directory /var/lib/nova/.ssh exists and contains the SSH keypair.
Add the following three options on /etc/ssh/ssh_config on the compute nodes, to disable host key identification:
```
CheckHostIP no
StrictHostKeyChecking no
UserKnownHostsFile /dev/null
```

This can be done with either of the following commands, for all units:

$ juju run --application nova-compute-ct1-cl1 'sudo printf "#   GARR for live migration\n    CheckHostIP no\n    StrictHostKeyChecking no\n    UserKnownHostsFile /dev/null\n" >> /etc/ssh/ssh_config'

or a specific one:

$ juju run --unit nova-compute-ct1-cl1/123 'sudo printf "#   GARR for live migration\n    CheckHostIP no\n    StrictHostKeyChecking no\n    UserKnownHostsFile /dev/null\n" >> /etc/ssh/ssh_config'