I have the same problem. I want to install OpenNebula 5.4.1 frontend and node on the same machine.
I followed your advices and I can login from the oneadmin user to ssh firstname.lastname@example.org without password. I have added node to Sunstone host and it works, monitoring are working perfectly, I can see memory usage, disk usage, etc. but when I’m trying to add any VM, in log I see the next error:
Wed Oct 4 20:08:31 2017 [Z0][TM][E]: clone: Command "scp -r ubuntu-2gb-fra1-01:/var/lib/one//datastores/1/39f6eaf43b14ef931810198cff0686ed 127.0.0.1:/var/lib/one//datastores/0/3/disk.0" failed: Host key verification failed.
Wed Oct 4 20:08:31 2017 [Z0][TM][E]: Error copying ubuntu-2gb-fra1-01:/var/lib/one//datastores/1/39f6eaf43b14ef931810198cff0686ed to 127.0.0.1:/var/lib/one//datastores/0/3/disk.0
Wed Oct 4 20:08:31 2017 [Z0][TM][I]: ExitCode: 1
Could you help me with it?