stack@picasso-demo-core-01:~$ docker run --rm -it --name ucp   -v /var/run/docker.sock:/var/run/docker.sock   docker/ucp join -i --fresh-install
INFO[0000] Your engine version 1.12.3, build 6b644ec (3.13.0-100-generic) is compatible
Please enter the URL to your UCP server: https://16.125.107.107
UCP server https://16.125.107.107
CA Subject: UCP Client Root CA
Serial Number: 525f2d3ae78976c8
SHA-256 Fingerprint=A6:94:96:33:22:40:54:7F:03:A2:77:0D:3F:DF:77:00:B4:42:3D:CB:F4:EB:32:5E:8C:1C:57:95:93:77:90:27
Do you want to trust this server and proceed with the join? (y/n): y
Please enter your UCP Admin username: admin
Please enter your UCP Admin password:
INFO[0019] All required images are present
WARN[0086] None of the hostnames we'll be using in the UCP certificates [picasso-demo-core-01 127.0.0.1 172.17.0.1 16.125.106.70] contain a domain component.  Your generated certs may fail TLS validation unless you only use one of these shortnames or IPs to connect.  You can use the --san flag to add more aliases

You may enter additional aliases (SANs) now or press enter to proceed with the above list.
Additional aliases:
INFO[0062] This engine will join UCP and advertise itself with host address 16.125.106.70 - If this is incorrect, please specify an alternative address with the '--host-address' flag
INFO[0062] Verifying your system is compatible with UCP
INFO[0070] Starting local swarm containers
ERRO[0175] We were unable to communicate with proxy we just started at address 16.125.106.70.  Did you forget to open your firewall ports?  Did you forget to specify an alternate DNS server with the '--dns' flag?  If this address is incorrect, re-run the install using the '--host-address' option.    Run "docker logs ucp-proxy" for more details from the proxy
FATA[0175] Unable to connect to system