Install and configure a compute node for Red Hat Enterprise Linux and CentOS¶

This section describes how to install and configure the Compute service on a compute node. The service supports several hypervisors to deploy instances or virtual machines (VMs). For simplicity, this configuration uses the Quick EMUlator (QEMU) hypervisor with the kernel-based VM (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:
```
# yum install openstack-nova-compute
```
Edit the /etc/nova/nova.conf file and complete the following actions:
- In the [DEFAULT] section, enable only the compute and metadata APIs:
```
[DEFAULT]
# ...
enabled_apis = osapi_compute,metadata
```
- 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 [api] and [keystone_authtoken] sections, configure Identity service access:
```
[api]
# ...
auth_strategy = keystone

[keystone_authtoken]
# ...
www_authenticate_uri = http://controller:5000/
auth_url = http://controller:5000/
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, configure the my_ip option:
```
[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 [DEFAULT] section, enable support for the Networking service:
```
[DEFAULT]
# ...
use_neutron = true
firewall_driver = nova.virt.firewall.NoopFirewallDriver
```
  Note
  
  By default, Compute uses an internal firewall service. Since Networking includes a firewall service, you must disable the Compute firewall service by using the nova.virt.firewall.NoopFirewallDriver firewall driver.
- Configure the [neutron] section of /etc/nova/nova.conf. Refer to the Networking service install guide for more details.
- In the [vnc] section, enable and configure remote console access:
```
[vnc]
# ...
enabled = true
server_listen = 0.0.0.0
server_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
```
- In the [oslo_concurrency] section, configure the lock path:
```
[oslo_concurrency]
# ...
lock_path = /var/lib/nova/tmp
```
- In the [placement] section, configure the Placement API:
```
[placement]
# ...
region_name = RegionOne
project_domain_name = Default
project_name = service
auth_type = password
user_domain_name = Default
auth_url = http://controller:5000/v3
username = placement
password = PLACEMENT_PASS
```
  Replace PLACEMENT_PASS with the password you choose for the placement user in the Identity service. Comment out any other options in the [placement] section.

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.
- Edit the [libvirt] section in the /etc/nova/nova.conf file as follows:
```
[libvirt]
# ...
virt_type = qemu
```

Start the Compute service including its dependencies and configure them to start automatically when the system boots:

# systemctl enable libvirtd.service openstack-nova-compute.service
# systemctl start libvirtd.service openstack-nova-compute.service

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. Configure the firewall to open port 5672 on the controller node and restart nova-compute service on the compute node.

Add the compute node to the cell database¶

Important

Run the following commands on the controller node.

Source the admin credentials to enable admin-only CLI commands, then confirm there are compute hosts in the database:

$ . admin-openrc

$ openstack compute service list --service nova-compute
+----+-------+--------------+------+-------+---------+----------------------------+
| ID | Host  | Binary       | Zone | State | Status  | Updated At                 |
+----+-------+--------------+------+-------+---------+----------------------------+
| 1  | node1 | nova-compute | nova | up    | enabled | 2017-04-14T15:30:44.000000 |
+----+-------+--------------+------+-------+---------+----------------------------+

Discover compute hosts:

# su -s /bin/sh -c "nova-manage cell_v2 discover_hosts --verbose" nova

Found 2 cell mappings.
Skipping cell0 since it does not contain hosts.
Getting compute nodes from cell 'cell1': ad5a5985-a719-4567-98d8-8d148aaae4bc
Found 1 computes in cell: ad5a5985-a719-4567-98d8-8d148aaae4bc
Checking host mapping for compute host 'compute': fe58ddc1-1d65-4f87-9456-bc040dc106b3
Creating host mapping for compute host 'compute': fe58ddc1-1d65-4f87-9456-bc040dc106b3

Note

When you add new compute nodes, you must run nova-manage cell_v2 discover_hosts on the controller node to register those new compute nodes. Alternatively, you can set an appropriate interval in /etc/nova/nova.conf:

[scheduler]
discover_hosts_in_cells_interval = 300