The VNC proxy is an OpenStack component that enables compute service users to access their instances through VNC clients. The VNC console connection works as follows: A user connects to the API and gets an access_url such as, http://ip:port/?token=xyz. The user pastes the URL in a browser or uses it as a client parameter. The browser or client connects to the proxy. The proxy talks to nova-consoleauth to authorize the token for the user, and maps the token to the private host and port of the VNC server for an instance. The compute host specifies the address that the proxy should use to connect through the nova.conf file option, vncserver_proxyclient_address. In this way, the VNC proxy works as a bridge between the public network and private host network. The proxy initiates the connection to VNC server and continues to proxy until the session ends. The proxy also tunnels the VNC protocol over WebSockets so that the noVNC client can talk to VNC servers. In general, the VNC proxy: Bridges between the public network where the clients live and the private network where VNC servers live. Mediates token authentication. Transparently deals with hypervisor-specific connection details to provide a uniform client experience.

Both client proxies leverage a shared service to manage token authentication called nova-consoleauth. This service must be running for either proxy to work. Many proxies of either type can be run against a single nova-consoleauth service in a cluster configuration. Do not confuse the nova-consoleauth shared service with nova-console, which is a XenAPI-specific service that most recent VNC proxy architectures do not use.

A typical deployment has the following components: A nova-consoleauth process. Typically runs on the controller host. One or more nova-novncproxy services. Supports browser-based noVNC clients. For simple deployments, this service typically runs on the same machine as nova-api because it operates as a proxy between the public network and the private compute host network. One or more nova-xvpvncproxy services. Supports the special Java client discussed here. For simple deployments, this service typically runs on the same machine as nova-api because it acts as a proxy between the public network and the private compute host network. One or more compute hosts. These compute hosts must have correctly configured options, as follows.

To customize the VNC console, use the following configuration options: To support live migration, you cannot specify a specific IP address for vncserver_listen, because that IP address does not exist on the destination host. The vncserver_proxyclient_address defaults to 127.0.0.1, which is the address of the compute host that Compute instructs proxies to use when connecting to instance servers. For all-in-one XenServer domU deployments, set this to 169.254.0.1. For multi-host XenServer domU deployments, set to a dom0 management IP on the same network as the proxies. For multi-host libvirt deployments, set to a host management IP on the same network as the proxies.

You must install the noVNC package, which contains the nova-novncproxy service. As root, run the following command: # apt-get install novnc The service starts automatically on installation. To restart the service, run: # service novnc restart The configuration option parameter should point to your nova.conf file, which includes the message queue server address and credentials. By default, nova-novncproxy binds on 0.0.0.0:6080. To connect the service to your Compute deployment, add the following configuration options to your nova.conf file: vncserver_listen=0.0.0.0 Specifies the address on which the VNC service should bind. Make sure it is assigned one of the compute node interfaces. This address is the one used by your domain file. <graphics type="vnc" autoport="yes" keymap="en-us" listen="0.0.0.0"/> To use live migration, use the 0.0.0.0 address. vncserver_proxyclient_address=127.0.0.1 The address of the compute host that Compute instructs proxies to use when connecting to instance vncservers.

Q: What is the difference between nova-xvpvncproxy and nova-novncproxy? A: nova-xvpvncproxy, which ships with OpenStack Compute, is a proxy that supports a simple Java client. nova-novncproxy uses noVNC to provide VNC support through a web browser. Q: I want VNC support in the OpenStack dashboard. What services do I need? A: You need nova-novncproxy, nova-consoleauth, and correctly configured compute hosts. Q: When I use nova get-vnc-console or click on the VNC tab of the OpenStack dashboard, it hangs. Why? A: Make sure you are running nova-consoleauth (in addition to nova-novncproxy). The proxies rely on nova-consoleauth to validate tokens, and waits for a reply from them until a timeout is reached. Q: My VNC proxy worked fine during my all-in-one test, but now it doesn't work on multi host. Why? A: The default options work for an all-in-one install, but changes must be made on your compute hosts once you start to build a cluster. As an example, suppose you have two servers: PROXYSERVER (public_ip=172.24.1.1, management_ip=192.168.1.1) COMPUTESERVER (management_ip=192.168.1.2) Your nova-compute configuration file must set the following values: # These flags help construct a connection data structure vncserver_proxyclient_address=192.168.1.2 novncproxy_base_url=http://172.24.1.1:6080/vnc_auto.html xvpvncproxy_base_url=http://172.24.1.1:6081/console # This is the address where the underlying vncserver (not the proxy) # will listen for connections. vncserver_listen=192.168.1.2 novncproxy_base_url and xvpvncproxy_base_url use a public IP; this is the URL that is ultimately returned to clients, which generally do not have access to your private network. Your PROXYSERVER must be able to reach vncserver_proxyclient_address, because that is the address over which the VNC connection is proxied. Q: My noVNC does not work with recent versions of web browsers. Why? A: Make sure you have installed python-numpy, which is required to support a newer version of the WebSocket protocol (HyBi-07+). Q: How do I adjust the dimensions of the VNC window image in the OpenStack dashboard? A: These values are hard-coded in a Django HTML template. To alter them, edit the _detail_vnc.html template file. The location of this file varies based on Linux distribution. On Ubuntu 12.04, the file is at /usr/share/pyshared/horizon/dashboards/nova/instances/templates/instances/_detail_vnc.html. Modify the width and height options, as follows: <iframe src="{{ vnc_url }}" width="720" height="430"></iframe>