Configure remote console access

OpenStack provides a number of different methods to interact with your guests: VNC, SPICE, Serial, RDP or MKS. If configured, these can be accessed by users through the OpenStack dashboard or the command line. This document outlines how these different technologies can be configured.

Overview

It is considered best practice to deploy only one of the consoles types and not all console types are supported by all compute drivers. Regardless of what option is chosen, a console proxy service is required. These proxy services are responsible for the following:

  • Provide a bridge between the public network where the clients live and the private network where the servers with consoles live.

  • Mediate token authentication.

  • Transparently handle hypervisor-specific connection details to provide a uniform client experience.

For some combinations of compute driver and console driver, these proxy services are provided by the hypervisor or another service. For all others, nova provides services to handle this proxying. Consider a noVNC-based VNC console connection for example:

  1. A user connects to the API and gets an access_url such as, http://ip:port/?path=%3Ftoken%3Dxyz.

  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 authorizes 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 vnc.server_proxyclient_address option. 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.

This means a typical deployment with noVNC-based VNC consoles will have the following components:

  • One or more nova-novncproxy service. 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-compute services. Hosts the instances for which consoles are provided.

Todo

The below diagram references nova-consoleauth and needs to be updated.

This particular example is illustrated below.

noVNC process

noVNC-based VNC console

VNC is a graphical console with wide support among many hypervisors and clients. noVNC provides VNC support through a web browser.

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, you need at least noVNC 1.0.0 for a fix.

If using VMware ESX/ESXi hypervisors, you need at least noVNC 1.1.0 for a fix.

Configuration

To enable the noVNC VNC console service, you must configure both the nova-novncproxy service and the nova-compute service. Most options are defined in the vnc group.

The nova-novncproxy service accepts the following options:

If using the libvirt compute driver and enabling VNC proxy security, the following additional options are supported:

For example, to configure this via a nova-novncproxy.conf file:

[vnc]
novncproxy_host = 0.0.0.0
novncproxy_port = 6082

Note

This doesn’t show configuration with security. For information on how to configure this, refer to VNC proxy security below.

The nova-compute service requires the following options to configure noVNC-based VNC console support:

If using the VMware compute driver, the following additional options are supported:

For example, to configure this via a nova.conf file:

[vnc]
enabled = True
novncproxy_base_url = http://IP_ADDRESS:6082/vnc_auto.html
server_listen = 127.0.0.1
server_proxyclient_address = 127.0.0.1

Replace IP_ADDRESS with the IP address from which the proxy is accessible by the outside world. For example, this may be the management interface IP address of the controller or the VIP.

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 2 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 1.

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.

Make sure to provide correct permissions to the certificate files for the process which creates instance. Please follow the libvirt wiki page 3 for the same.

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 2 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

SPICE console

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 with the nova-spicehtml5proxy service by using SPICE-over-websockets. The nova-spicehtml5proxy service communicates directly with the hypervisor process by using SPICE.

Configuration

Important

VNC must be explicitly disabled to get access to the SPICE console. Set the vnc.enabled option to False to disable the VNC console.

To enable the SPICE console service, you must configure both the nova-spicehtml5proxy service and the nova-compute service. Most options are defined in the spice group.

The nova-spicehtml5proxy service accepts the following options.

For example, to configure this via a nova-spicehtml5proxy.conf file:

[spice]
html5proxy_host = 0.0.0.0
html5proxy_port = 6082

The nova-compute service requires the following options to configure SPICE console support.

For example, to configure this via a nova.conf file:

[spice]
agent_enabled = False
enabled = True
html5proxy_base_url = http://IP_ADDRESS:6082/spice_auto.html
server_listen = 127.0.0.1
server_proxyclient_address = 127.0.0.1

Replace IP_ADDRESS with the IP address from which the proxy is accessible by the outside world. For example, this may be the management interface IP address of the controller or the VIP.

Optionally, the nova-compute service supports the following additional options to configure compression settings (algorithms and modes) for SPICE consoles.

Serial

Serial consoles provide an alternative to graphical consoles like VNC or SPICE. They work a little differently to graphical consoles so an example is beneficial. 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 (or ironic conductor, for ironic) to the guest.

Configuration

To enable the serial console service, you must configure both the nova-serialproxy service and the nova-compute service. Most options are defined in the serial_console group.

The nova-serialproxy service accepts the following options.

For example, to configure this via a nova-serialproxy.conf file:

[serial_console]
serialproxy_host = 0.0.0.0
serialproxy_port = 6083

The nova-compute service requires the following options to configure serial console support.

For example, to configure this via a nova.conf file:

[serial_console]
enabled = True
base_url = ws://IP_ADDRESS:6083/
proxyclient_address = 127.0.0.1
port_range = 10000:20000

Replace IP_ADDRESS with the IP address from which the proxy is accessible by the outside world. For example, this may be the management interface IP address of the controller or the VIP.

There are some things to keep in mind when configuring these options:

RDP

RDP is a graphical console primarily used with Hyper-V. Nova does not provide a console proxy service for RDP - instead, an external proxy service, such as the wsgate application provided by FreeRDP-WebConnect, should be used.

Configuration

To enable the RDP console service, you must configure both a console proxy service like wsgate and the nova-compute service. All options for the latter service are defined in the rdp group.

Information on configuring an RDP console proxy service, such as wsgate, is not provided here. However, more information can be found at cloudbase.it.

The nova-compute service requires the following options to configure RDP console support.

For example, to configure this via a nova.conf file:

[rdp]
enabled = True
html5_proxy_base_url = https://IP_ADDRESS:6083/

Replace IP_ADDRESS with the IP address from which the proxy is accessible by the outside world. For example, this may be the management interface IP address of the controller or the VIP.

MKS

MKS is the protocol used for accessing the console of a virtual machine running on VMware vSphere. It is very similar to VNC. Due to the architecture of the VMware vSphere hypervisor, it is not necessary to run a console proxy service.

Configuration

To enable the MKS console service, only the nova-compute service must be configured. All options are defined in the mks group.

The nova-compute service requires the following options to configure MKS console support.

For example, to configure this via a nova.conf file:

[mks]
enabled = True
mksproxy_base_url = https://127.0.0.1:6090/

About nova-consoleauth

The now-removed nova-consoleauth service was previously used to provide a shared service to manage token authentication that the client proxies outlined below could leverage. Token authentication was moved to the database in 18.0.0 (Rocky) and the service was removed in 20.0.0 (Train).

Frequently Asked Questions

  • Q: I want VNC support in the OpenStack dashboard. What services do I need?

    A: You need nova-novncproxy and correctly configured compute hosts.

  • 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

# 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 uses 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.

References

1

https://qemu.weilnetz.de/doc/4.2/qemu-doc.html#vnc_005fsec_005fcertificate_005fverify

2(1,2)

https://tools.ietf.org/html/rfc3280#section-4.2.1.10

3

https://wiki.libvirt.org/page/VNCTLSSetup#Changes_to_be_made_on_the_virtualisation_host_server