# Attaching a Volume to an Existing OpenStack Instance

When performing a restore from a backup of an OpenStack instance, you can attach a volume to a different instance. By attaching a volume to an existing instance, you can access or reuse the data on the volume without restoring the full source instance.

This type of restore is useful in the following scenarios:

- An instance has multiple volumes, but you want to restore only some of the volumes.

- You want to copy and add volumes from one instance to another instance.

- You want to quickly restore a volume and access the data on the volume.

## Limitations

You can attach a volume to an existing instance and perform cinder volume restore operations only for cinder volumes, not for images. If you select an image for a restore operation that attaches a volume to a different, existing instance or if you perform a cinder volume restore operation on an image, the job might fail.

## Multiattach Volumes in OpenStack

OpenStack no longer accepts the `multiattach` parameter in volume creation API calls. Instead, `multiattach` functionality is now managed by the volume type selected during creation. To successfully create a `multiattach` enabled volume, the volume type you choose must support multiattach. If an unsupported volume type is used, or if the deprecated multiattach parameter is included, volume creation will fail—especially during restore operations.

To accommodate this change, use the bDisableOpenStackVolumeMultiAttach additional setting.

## Prerequisites

If a passkey is configured for restores, you must have the passkey.

## Procedure

1. From the Command Center navigation pane, go to Protect > Virtual machines.

   The Overview page appears.

2. Click the VM groups tab.

   The VM group page appears. The VM groups area displays summary information for existing VM groups.

3. On the VM groups tab, in the row for the VM group, click the action button , and then click Restore.

   The Select restore type page appears.

4. To restore individual volumes and attach volumes to an existing instance, select Attach volume to existing VM.

   The Restore page appears.

5. To select a specific MediaAgent and/or source for the restore, in the upper-right area of the page, click the Settings button .

   By default, the Commvault software automatically selects the MediaAgent and source as follows:

   - MediaAgent: The software uses the MediaAgent that performed the backup.

   - Source: By default, the software searches for the requested data in the primary copy. If the data is not found in the primary copy, the software selects a secondary or auxiliary copy.

   For more information, see MediaAgent and Copy Precedence Considerations for Virtualization Restores.

6. Select the objects to restore, and then click Restore.

   The Restore Options dialog box appears as follows:

   - For admin users, both the Other Virtual Machine and the My Virtual Machine tabs display. Admin Users should choose one of the tabs and continue either to the Other Virtual Machine Tab or the My Virtual Machine Tab sections that follow.

   - For end users, the My Virtual Machine tab appears alone. End Users should continue to the My Virtual Machine Tab section that follows.

## Other Virtual Machine Tab

1. Specify the following information:

   1. Destination hypervisor: To restore to an instance on a different hypervisor, select the hypervisor from the list.

   2. Access node (optional): To use a different proxy, select the proxy from the list.

      By default, the instance volume is restored using the same proxy as the backup.

   3. For each volume you are restoring, specify the following information:

      - Change disk name to (optional): Enter a new display name for the disk.

        If a name was not specified for a disk under the source instance, the disk ID for the source disk is displayed for the disk, and the disk ID is used to name the restored disk unless you enter a different value in the Change disk name to box.

      - Restore to existing instance: Click Browse to select the instance to which you want to attach the restored image.

      - Availability zone: Click Browse to select the zone for the disk.

      - Volume type: Select a volume type that is defined for the zone of the destination disks.

        If the volume type was not explicitly set during the instance creation, and therefore, set to default, then, during the attach volume restore, you might need to explicitly select a volume type.

2. Click Submit.

## My Virtual Machine Tab

1. From the Select destination VM list, select the existing VM where you want to attach the disk.

2. You can rename the disk while it is attached for the restore. If you want to rename the disk, select the disk you want to attach, and in the Disk Name field, enter the name of the disk.

3. Select the Unconditionally overwrite if it already exists toggle to overwrite an existing disk.

4. If you do not want to receive an email when the backup job completes, unselect the When the job completes, notify me via email checkbox.

5. Click Submit.

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