Managing instances

Managing instances

This chapter describes how to create and access instances.

Creating an instance using the Dashboard

Using an image, create a new instance via the Dashboard options.

  1. Log into the Dashboard, and select the Compute project from the drop down list.

  2. Click the Images option.

  3. Locate the image that will act as the instance base from the Images table.

  4. Click Launch from the Actions column.

  5. Check the Launch Instances dialog, and find the details tab. Enter the appropriate values for the instance.

    1. In the Launch Instance dialog, click the Access & Security tab. Select the keypair. Set the security group as “default”.

    2. Click the Networking tab. This tab will be unavailable if OpenStack networking (neutron) has not been enabled. If networking is enabled, select the networks on which the instance will reside.

    3. Click the Volume Options tab. This tab will only be available if a Block Storage volume exists for the instance. Select Don’t boot from a volume for now.

      For more information on attaching Block Storage volumes to instances for persistent storage, see the Managing volumes for persistent storage section below.

    4. Add customisation scripts, if needed, by clicking the Post-Creation tab. These run after the instance has been created. Some instances support user data, such as root passwords, or admin users. Enter the information specific to the instance here if required.

    5. Click Advanced Options. Specify whether the instance uses a configuration drive to store metadata by selecting a disk partition type.

  6. Click Launch to create the instance. The instance will start on a compute node. The Instance page will open and start creating a new instance. The Instance page that opens will list the instance name, size, status, and task. Power state and public and private IP addresses are also listed here.

    The process will take less than a minute to complete. Instance creation is complete when the status is listed as active. Refresh the page to see the new active instance.

    Launching an instance options
    Field Name Required Details
    Availability Zone Optional The availability zone in which the image service creates the instance. If no availability zones is defined, no instances will be found. The cloud provider sets the availability zone to a specific value.
    Instance Name Required The name of the new instance, which becomes the initial host name of the server. If the server name is changed in the API or directly changed, the Dashboard names remain unchanged
    Image Required The type of container format, one of ami, ari, aki, bare, or ovf
    Flavor Required The vCPU, Memory, and Disk configuration. Note that larger flavors can take a long time to create. If creating an instance for the first time and want something small with which to test, select m1.small.
    Instance Count Required If creating multiple instances with this configuration, enter an integer up to the number permitted by the quota, which is 10 by default.
    Instance Boot Source Required Specify whether the instance will be based on an image or a snapshot. If it is the first time creating an instance, there will not yet be any snapshots available.
    Image Name Required The instance will boot from the selected image. This option will be pre-populated with the instance selected from the table. However, choose Boot from Snapshot in Instance Boot Source, and it will default to Snapshot instead.
    Security Groups Optional This option assigns security groups to an instance. The default security group activates when no customised group is specified here. Security Groups, similar to a cloud firewall, define which incoming network traffic is forwarded to instances.
    Keypair Optional Specify a key pair with this option. If the image uses a static key set (not recommended), a key pair is not needed.
    Selected Networks Optional To add a network to an instance, click the + in the Networks field.
    Customisation Script Optional Specify a customisation script. This script runs after the instance launches and becomes active.

Creating an instance using the command line

On the command line, instance creation is managed with the openstack server create command. Before launching an instance, determine what images and flavors are available to create a new instance using the openstack image list and openstack flavor list commands.

  1. Log in to any utility container.

  2. Issue the openstack server create command with a name for the instance, along with the name of the image and flavor to use:

    $ openstack server create --image precise-image --flavor=2 --key-name example-key example-instance
    |               Property              |                Value                 |
    |          OS-DCF:diskConfig          |                MANUAL                |
    |         OS-EXT-SRV-ATTR:host        |                 None                 |
    | OS-EXT-SRV-ATTR:hypervisor_hostname |                 None                 |
    |    OS-EXT-SRV-ATTR:instance_name    |          instance-0000000d           |
    |        OS-EXT-STS:power_state       |                  0                   |
    |        OS-EXT-STS:task_state        |              scheduling              |
    |         OS-EXT-STS:vm_state         |               building               |
    |              accessIPv4             |                                      |
    |              accessIPv6             |                                      |
    |              adminPass              |             ATSEfRY9fZPx             |
    |             config_drive            |                                      |
    |               created               |         2012-08-02T15:43:46Z         |
    |                flavor               |               m1.small               |
    |                hostId               |                                      |
    |                  id                 | 5bf46a3b-084c-4ce1-b06f-e460e875075b |
    |                image                |             precise-image            |
    |               key_name              |              example-key             |
    |               metadata              |                  {}                  |
    |                 name                |           example-instance           |
    |               progress              |                  0                   |
    |                status               |                BUILD                 |
    |              tenant_id              |   b4769145977045e2a9279c842b09be6a   |
    |               updated               |         2012-08-02T15:43:46Z         |
    |               user_id               |   5f2f2c28bdc844f9845251290b524e80   |
  3. To check that the instance was created successfully, issue the openstack server list command:

    $ openstack server list
    |        ID        |       Name       | Status |      Networks     |   Image Name  |
    | [ID truncated]   | example-instance | ACTIVE |  public= | precise-image |

Managing an instance

  1. Log in to the Dashboard. Select one of the projects, and click Instances.
  2. Select an instance from the list of available instances.
  3. Check the Actions column, and click on the More option. Select the instance state.

The Actions column includes the following options:

  • Resize or rebuild any instance
  • View the instance console log
  • Edit the instance
  • Modify security groups
  • Pause, resume, or suspend the instance
  • Soft or hard reset the instance


Terminate the instance under the Actions column.

Managing volumes for persistent storage

Volumes attach to instances, enabling persistent storage. Volume storage provides a source of memory for instances. Administrators can attach volumes to a running instance, or move a volume from one instance to another.

Nova instances live migration

Nova is capable of live migration instances from one host to a different host to support various operational tasks including:

  • Host Maintenance
  • Host capacity management
  • Resizing and moving instances to better hardware

Nova configuration drive implication

Depending on the OpenStack-Ansible version in use, Nova can be configured to force configuration drive attachments to instances. In this case, a ISO9660 CD-ROM image will be made available to the instance via the /mnt mount point. This can be used by tools, such as cloud-init, to gain access to instance metadata. This is an alternative way of accessing the Nova EC2-style Metadata.

To allow live migration of Nova instances, this forced provisioning of the config (CD-ROM) drive needs either be turned off, or the format of the configuration drive needs to be changed to a disk format like vfat, a format which both Linux and Windows instances can access.

This work around is required for all Libvirt versions prior 1.2.17.

To turn off the forced provisioning of the config drive, add the following override to the /etc/openstack_deploy/user_variables.yml file:

nova_force_config_drive: False

To change the format of the configuration drive, to a hard disk style format, use the following configuration inside the same /etc/openstack_deploy/user_variables.yml file:

    config_drive_format: vfat
    force_config_drive: false

Tunneling versus direct transport

In the default configuration, Nova determines the correct transport URL for how to transfer the data from one host to the other. Depending on the nova_virt_type override the following configurations are used:

  • kvm defaults to qemu+tcp://%s/system
  • qemu defaults to qemu+tcp://%s/system
  • xen defaults to xenmigr://%s/system

Libvirt TCP port to transfer the data to migrate.

OpenStack-Ansible changes the default setting and used a encrypted SSH connection to transfer the instance data.

live_migration_uri = "qemu+ssh://nova@%s/system?no_verify=1&keyfile={{ nova_system_home_folder }}/.ssh/id_rsa"

Other configurations can be configured inside the /etc/openstack_deploy/user_variables.yml file:

    live_migration_completion_timeout: 0
    live_migration_progress_timeout: 0
    live_migration_uri: "qemu+ssh://nova@%s/system?keyfile=/var/lib/nova/.ssh/id_rsa&no_verify=1"

Local versus shared storage

By default, live migration assumes that your Nova instances are stored on shared storage and KVM/Libvirt only need to synchronize the memory and base image of the Nova instance to the new host. Live migrations on local storage will fail as a result of that assumption. Migrations with local storage can be accomplished by allowing instance disk migrations with the --block-migrate option.

Additional Nova flavor features like ephemeral storage or swap have an impact on live migration performance and success.

Cinder attached volumes also require a Libvirt version larger or equal to 1.2.17.

Executing the migration

The live migration is accessible via the nova client.

nova live-migration [--block-migrate] [--force] <uuid> [<host>]

Examplarery live migration on a local storage:

nova live-migration --block-migrate <uuid of the instance> <nova host>

Monitoring the status

Once the live migration request has been accepted, the status can be monitored with the nova client:

nova migration-list

| Id | Source Node | Dest Node | Source Compute | Dest Compute | Dest Host | Status    | Instance UUID | Old Flavor | New Flavor | Created At | Updated At | Type            |
| 6  | -           | -         | compute01      | compute02    | -         | preparing | f95ee17a-d09c | 7          | 7          | date       | date       | live-migration  |

To filter the list, the options --host or --status can be used:

nova migration-list --status error

In cases where the live migration fails, both the source and destination compute nodes need to be checked for errors. Usually it is sufficient to search for the instance UUID only to find errors related to the live migration.

Other forms of instance migration

Besides the live migration, Nova offers the option to migrate entire hosts in a online (live) or offline (cold) migration.

The following nova client commands are provided:

  • host-evacuate-live

    Live migrate all instances of the specified host to other hosts if resource utilzation allows. It is best to use shared storage like Ceph or NFS for host evacuation.

  • host-servers-migrate

    This command is similar to host evacuation but migrates all instances off the specified host while they are shutdown.

  • resize

    Changes the flavor of an Nova instance (increase) while rebooting and also migrates (cold) the instance to a new host to accommodate the new resource requirements. This operation can take considerate amount of time, depending disk image sizes.

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