nova/nova/tests/functional/api_sample_tests/api_samples/servers/v2.90/server-update-req.json.tpl

{
    "server": {
        "accessIPv4": "%(access_ip_v4)s",
        "accessIPv6": "%(access_ip_v6)s",
        "OS-DCF:diskConfig": "AUTO",
        "hostname": "new-server-hostname"
    }
}