Select hosts where instances are launched¶

With the appropriate permissions, you can select which host instances are launched on and which roles can boot instances on this host.

Starting with the 2.74 microversion, there are two ways to specify a host and/or node when creating a server.

Using Explicit Host and/or Node¶

We can create servers by using explicit host and/or node. When we use this way to request where instances are launched, we will still execute scheduler filters on the requested destination.

To select the host where instances are launched, use the --host HOST and/or --hypervisor-hostname HYPERVISOR options on the openstack server create command.

For example:

$ openstack --os-compute-api-version 2.74 server create --image IMAGE \
--flavor m1.tiny --key-name KEY --host HOST \
--hypervisor-hostname HYPERVISOR --nic net-id=UUID SERVER

To specify which roles can launch an instance on a specified host, enable the compute:servers:create:requested_destination rule in the policy.json file. By default, this rule is enabled for only the admin role. If you see Forbidden (HTTP 403) in the response, then you are not using the required credentials.
To view the list of valid compute hosts and nodes, you can follow Finding Host and Node Names.

[Legacy] Using Host and/or Node with Availability Zone¶

We can create servers by using host and/or node with availability zone. When we use this way to select hosts where instances are launched, we will not run the scheduler filters.

To select the host where instances are launched, use the --availability-zone ZONE:HOST:NODE parameter on the openstack server create command.

For example:
```
$ openstack server create --image IMAGE --flavor m1.tiny --key-name KEY \
--availability-zone ZONE:HOST:NODE --nic net-id=UUID SERVER
```
Note

HOST and NODE are optional parameters. In such cases, use the --availability-zone ZONE::NODE, --availability-zone ZONE:HOST or --availability-zone ZONE.
To specify which roles can launch an instance on a specified host, enable the os_compute_api:servers:create:forced_host rule in the policy.json file. By default, this rule is enabled for only the admin role. If you see Forbidden (HTTP 403) in return, then you are not using the required credentials.

To view the list of valid zones, use the openstack availability zone list --compute command.

$ openstack availability zone list --compute
+-----------+-------------+
| Zone Name | Zone Status |
+-----------+-------------+
| zone1     | available   |
| zone2     | available   |
+-----------+-------------+

To view the list of valid compute hosts and nodes, you can follow Finding Host and Node Names.

Finding Host and Node Names¶

To view the list of valid compute hosts, use the openstack compute service list --service nova-compute command.

$ openstack compute service list --service nova-compute
+----+--------------+---------------+------+---------+-------+----------------------------+
| ID | Binary       | Host          | Zone | Status  | State | Updated At                 |
+----+--------------+---------------+------+---------+-------+----------------------------+
| 10 | nova-compute | compute01     | nova | enabled | up    | 2019-07-09T03:59:19.000000 |
| 11 | nova-compute | compute02     | nova | enabled | up    | 2019-07-09T03:59:19.000000 |
| 12 | nova-compute | compute03     | nova | enabled | up    | 2019-07-09T03:59:19.000000 |
+----+--------------+---------------+------+---------+-------+----------------------------+

To view the list of valid compute nodes, use the openstack hypervisor list command.

$ openstack hypervisor list
+----+---------------------+-----------------+---------------+-------+
| ID | Hypervisor Hostname | Hypervisor Type | Host IP       | State |
+----+---------------------+-----------------+---------------+-------+
|  6 | compute01           | QEMU            | 172.16.50.100 | up    |
|  7 | compute02           | QEMU            | 172.16.50.101 | up    |
|  8 | compute03           | QEMU            | 172.16.50.102 | up    |
+----+---------------------+-----------------+---------------+-------+