Configure remote console access

Configure remote console access

To provide a remote console or remote desktop access to guest virtual machines, use VNC, SPICE HTML5 or Serial through either the OpenStack dashboard or the command line. Best practice is to select only one of them to run.

About nova-consoleauth

The 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.

Deprecated since version 18.0.0: nova-consoleauth is deprecated since 18.0.0 (Rocky) and will be removed in an upcoming release.

SPICE console

OpenStack Compute supports VNC consoles to guests. The VNC protocol is fairly limited, lacking support for multiple monitors, bi-directional audio, reliable cut-and-paste, video streaming and more. SPICE is a new protocol that aims to address the limitations in VNC and provide good remote desktop support.

SPICE support in OpenStack Compute shares a similar architecture to the VNC implementation. The OpenStack dashboard uses a SPICE-HTML5 widget in its console tab that communicates to the nova-spicehtml5proxy service by using SPICE-over-websockets. The nova-spicehtml5proxy service communicates directly with the hypervisor process by using SPICE.

VNC must be explicitly disabled to get access to the SPICE console. Set the vnc_enabled option to False in the [DEFAULT] section to disable the VNC console.

Use the following options to configure SPICE as the console for OpenStack Compute:

[spice]
agent_enabled = False
enabled = True
html5proxy_base_url = http://IP_ADDRESS:6082/spice_auto.html
html5proxy_host = 0.0.0.0
html5proxy_port = 6082
keymap = en-us
server_listen = 127.0.0.1
server_proxyclient_address = 127.0.0.1

Replace IP_ADDRESS with the management interface IP address of the controller or the VIP.

VNC console proxy

The VNC proxy is an OpenStack component that enables compute service users to access their instances through VNC clients.

Note

The web proxy console URLs do not support the websocket protocol scheme (ws://) on python versions less than 2.7.4.

The VNC console connection works as follows:

  1. A user connects to the API and gets an access_url such as, http://ip:port/?token=xyz.

  2. The user pastes the URL in a browser or uses it as a client parameter.

  3. The browser or client connects to the proxy.

  4. 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, server_proxyclient_address. In this way, the VNC proxy works as a bridge between the public network and private host network.

  5. 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.
noVNC process

VNC proxy security

Deploy the public-facing interface of the VNC proxy with HTTPS to prevent attacks from malicious parties on the network between the tenant user and proxy server. When using HTTPS, the TLS encryption only applies to data between the tenant user and proxy server. The data between the proxy server and Compute node instance will still be unencrypted. To provide protection for the latter, it is necessary to enable the VeNCrypt authentication scheme for VNC in both the Compute nodes and noVNC proxy server hosts.

QEMU/KVM Compute node configuration

Ensure each Compute node running QEMU/KVM with libvirt has a set of certificates issued to it. The following is a list of the required certificates:

  • /etc/pki/libvirt-vnc/server-cert.pem

    An x509 certificate to be presented by the VNC server. The CommonName should match the primary hostname of the compute node. Use of subjectAltName is also permitted if there is a need to use multiple hostnames or IP addresses to access the same Compute node.

  • /etc/pki/libvirt-vnc/server-key.pem

    The private key used to generate the server-cert.pem file.

  • /etc/pki/libvirt-vnc/ca-cert.pem

    The authority certificate used to sign server-cert.pem and sign the VNC proxy server certificates.

The certificates must have v3 basic constraints [3] present to indicate the permitted key use and purpose data.

We recommend using a dedicated certificate authority solely for the VNC service. This authority may be a child of the master certificate authority used for the OpenStack deployment. This is because libvirt does not currently have a mechanism to restrict what certificates can be presented by the proxy server.

For further details on certificate creation, consult the QEMU manual page documentation on VNC server certificate setup [2].

Configure libvirt to enable the VeNCrypt authentication scheme for the VNC server. In /etc/libvirt/qemu.conf, uncomment the following settings:

  • vnc_tls=1

    This instructs libvirt to enable the VeNCrypt authentication scheme when launching QEMU, passing it the certificates shown above.

  • vnc_tls_x509_verify=1

    This instructs QEMU to require that all VNC clients present a valid x509 certificate. Assuming a dedicated certificate authority is used for the VNC service, this ensures that only approved VNC proxy servers can connect to the Compute nodes.

After editing qemu.conf, the libvirtd service must be restarted:

$ systemctl restart libvirtd.service

Changes will not apply to any existing running guests on the Compute node, so this configuration should be done before launching any instances.

noVNC proxy server configuration

The noVNC proxy server initially only supports the none authentication scheme, which does no checking. Therefore, it is necessary to enable the vencrypt authentication scheme by editing the nova.conf file to set.

[vnc]
auth_schemes=vencrypt,none

The vnc.auth_schemes values should be listed in order of preference. If enabling VeNCrypt on an existing deployment which already has instances running, the noVNC proxy server must initially be allowed to use vencrypt and none. Once it is confirmed that all Compute nodes have VeNCrypt enabled for VNC, it is possible to remove the none option from the list of the vnc.auth_schemes values.

At that point, the noVNC proxy will refuse to connect to any Compute node that does not offer VeNCrypt.

As well as enabling the authentication scheme, it is necessary to provide certificates to the noVNC proxy.

  • /etc/pki/nova-novncproxy/client-cert.pem

    An x509 certificate to be presented to the VNC server. While libvirt/QEMU will not currently do any validation of the CommonName field, future versions will allow for setting up access controls based on the CommonName. The CommonName field should match the primary hostname of the controller node. If using a HA deployment, the Organization field can also be configured to a value that is common across all console proxy instances in the deployment. This avoids the need to modify each compute node’s whitelist every time a console proxy instance is added or removed.

  • /etc/pki/nova-novncproxy/client-key.pem

    The private key used to generate the client-cert.pem file.

  • /etc/pki/nova-novncproxy/ca-cert.pem

    The certificate authority cert used to sign client-cert.pem and sign the compute node VNC server certificates.

The certificates must have v3 basic constraints [3] present to indicate the permitted key use and purpose data.

Once the certificates have been created, the noVNC console proxy service must be told where to find them. This requires editing nova.conf to set.

[vnc]
vencrypt_client_key=/etc/pki/nova-novncproxy/client-key.pem
vencrypt_client_cert=/etc/pki/nova-novncproxy/client-cert.pem
vencrypt_ca_certs=/etc/pki/nova-novncproxy/ca-cert.pem

VNC configuration options

To customize the VNC console, use the following configuration options in your nova.conf file:

Note

To support live migration, you cannot specify a specific IP address for server_listen, because that IP address does not exist on the destination host.

Description of VNC configuration options
Configuration option = Default value Description
[DEFAULT]  
daemon = False (BoolOpt) Become a daemon (background process)
key = None (StrOpt) SSL key file (if separate from cert)
novncproxy_host = 0.0.0.0 (StrOpt) Host on which to listen for incoming requests
novncproxy_port = 6080 (IntOpt) Port on which to listen for incoming requests
record = False (BoolOpt) Record sessions to FILE.[session_number]
source_is_ipv6 = False (BoolOpt) Source is ipv6
ssl_only = False (BoolOpt) Disallow non-encrypted connections
web = /usr/share/spice-html5 (StrOpt) Run webserver on same port. Serve files from DIR.
[vmware]  
vnc_port = 5900 (IntOpt) VNC starting port
vnc_port_total = 10000 vnc_port_total = 10000
[vnc]  
enabled = True (BoolOpt) Enable VNC related features
novncproxy_base_url = http://127.0.0.1:6080/vnc_auto.html (StrOpt) Location of VNC console proxy, in the form “http://127.0.0.1:6080/vnc_auto.html
server_listen = 127.0.0.1 (StrOpt) IP address on which instance vncservers should listen
server_proxyclient_address = 127.0.0.1 (StrOpt) The address to which proxy clients (like nova-xvpvncproxy) should connect
xvpvncproxy_base_url = http://127.0.0.1:6081/console (StrOpt) Location of nova xvp VNC console proxy, in the form “http://127.0.0.1:6081/console

Note

  • The server_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.

Typical deployment

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.

nova-novncproxy (noVNC)

You must install the noVNC package, which contains the nova-novncproxy service. As root, run the following command:

# apt-get install nova-novncproxy

Note

It has been reported that versions of noVNC older than 0.6 do not work with the nova-novncproxy service.

If using non-US key mappings, then you need at least noVNC 1.0.0 for a fix.

The service starts automatically on installation.

To restart the service, run:

# service nova-novncproxy 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:

  • server_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"/>
    

    Note

    To use live migration, use the 0.0.0.0 address.

  • server_proxyclient_address=127.0.0.1

    The address of the compute host that Compute instructs proxies to use when connecting to instance vncservers.

Frequently asked questions about VNC access to virtual machines

  • 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:

    [vnc]
    # These flags help construct a connection data structure
    server_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.
    server_listen=192.168.1.2
    

    Note

    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 server_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 14.04, 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>
    
  • Q: My noVNC connections failed with ValidationError: Origin header protocol does not match. Why?

    A: Make sure the base_url match your TLS setting. If you are using https console connections, make sure that the value of novncproxy_base_url is set explicitly where the nova-novncproxy service is running.

Serial Console

The serial console feature [1] in nova is an alternative for graphical consoles like VNC, SPICE, RDP. The example below uses these nodes:

  • controller node with IP 192.168.50.100
  • compute node 1 with IP 192.168.50.104
  • compute node 2 with IP 192.168.50.105

Here’s the general flow of actions:

The serial console flow
  1. The user requests a serial console connection string for an instance from the REST API.
  2. The nova-api service asks the nova-compute service, which manages that instance, to fulfill that request.
  3. That connection string gets used by the user to connect to the nova-serialproxy service.
  4. The nova-serialproxy service then proxies the console interaction to the port of the compute node where the instance is running. That port gets forwarded by the hypervisor into the KVM guest.

The config options for those nodes, which are in the section [serial_console] of your nova.conf, are not intuitive at first. Keep these things in mind:

  • The serialproxy_host is the address the nova-serialproxy service listens to for incoming connections (see step 3).
  • The serialproxy_port value must be the very same as in the URI of base_url.
  • The base_url on the compute node will be part of the response the user will get when asking for a serial console connection string (see step 1 from above). This means it needs to be an URL the user can connect to.
  • The proxyclient_address on the compute node will be used by the nova-serialproxy service to determine where to connect to for proxying the console interaction.
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