Install and configure a compute node¶

This section describes how to install and configure the Compute service on a compute node. The service supports several hypervisors to deploy instances or VMs. For simplicity, this configuration uses the QEMU hypervisor with the KVM extension on compute nodes that support hardware acceleration for virtual machines. On legacy hardware, this configuration uses the generic QEMU hypervisor. You can follow these instructions with minor modifications to horizontally scale your environment with additional compute nodes.

Note

This section assumes that you are following the instructions in this guide step-by-step to configure the first compute node. If you want to configure additional compute nodes, prepare them in a similar fashion to the first compute node in the example architectures section. Each additional compute node requires a unique IP address.

Install and configure components¶

Note

Default configuration files vary by distribution. You might need to add these sections and options rather than modifying existing sections and options. Also, an ellipsis (...) in the configuration snippets indicates potential default configuration options that you should retain.

Install the packages:
```
# apt install nova-compute
```

Edit the /etc/nova/nova.conf file and complete the following actions:
- In the [DEFAULT] section, configure RabbitMQ message queue access:
```
[DEFAULT]
...
transport_url = rabbit://openstack:RABBIT_PASS@controller
```
  Replace RABBIT_PASS with the password you chose for the openstack account in RabbitMQ.
- In the [DEFAULT] and [keystone_authtoken] sections, configure Identity service access:
```
[DEFAULT]
...
auth_strategy = keystone

[keystone_authtoken]
...
auth_uri = http://controller:5000
auth_url = http://controller:35357
memcached_servers = controller:11211
auth_type = password
project_domain_name = Default
user_domain_name = Default
project_name = service
username = nova
password = NOVA_PASS
```
  Replace NOVA_PASS with the password you chose for the nova user in the Identity service.
  
  Note
  
  Comment out or remove any other options in the [keystone_authtoken] section.
- In the [DEFAULT] section, check that the my_ip option is correctly set (this value is handled by the config and postinst scripts of the nova-common package using debconf):
```
[DEFAULT]
...
my_ip = MANAGEMENT_INTERFACE_IP_ADDRESS
```
  Replace MANAGEMENT_INTERFACE_IP_ADDRESS with the IP address of the management network interface on your compute node, typically 10.0.0.31 for the first node in the example architecture.
- In the [vnc] section, enable and configure remote console access:
```
[vnc]
...
enabled = True
vncserver_listen = 0.0.0.0
vncserver_proxyclient_address = $my_ip
novncproxy_base_url = http://controller:6080/vnc_auto.html
```
  The server component listens on all IP addresses and the proxy component only listens on the management interface IP address of the compute node. The base URL indicates the location where you can use a web browser to access remote consoles of instances on this compute node.
  
  Note
  
  If the web browser to access remote consoles resides on a host that cannot resolve the controller hostname, you must replace controller with the management interface IP address of the controller node.
- In the [glance] section, configure the location of the Image service API:
```
[glance]
...
api_servers = http://controller:9292
```

Ensure the kernel module nbd is loaded.
```
# modprobe nbd
```
Ensure the module loads on every boot by adding nbd to the /etc/modules-load.d/nbd.conf file.

Finalize installation¶

Determine whether your compute node supports hardware acceleration for virtual machines:
```
$ egrep -c '(vmx|svm)' /proc/cpuinfo
```
If this command returns a value of one or greater, your compute node supports hardware acceleration which typically requires no additional configuration.

If this command returns a value of zero, your compute node does not support hardware acceleration and you must configure libvirt to use QEMU instead of KVM.
- Replace the nova-compute-kvm package with nova-compute-qemu which automatically changes the /etc/nova/nova-compute.conf file and installs the necessary dependencies:
```
# apt install nova-compute-qemu
```

Restart the Compute service:
```
# service nova-compute restart
```

Note

If the nova-compute service fails to start, check /var/log/nova/nova-compute.log. The error message AMQP server on controller:5672 is unreachable likely indicates that the firewall on the controller node is preventing access to port 5672.