Determining the Boot Source of an Instance

If your organization uses a block storage solution, it can require that Metacloud users launch instances from volumes rather than from computer server drives. If you are using the CLI or API calls to launch instances, you need to specify a block storage root disk. See Specifying Boot from Volume in CLI or API.

If you are not sure whether a given instance was booted from a volume or a computer server drive, take the following steps to determine the boot method:

  1. Run openstack server list to get the UUID for the instance that you want to determine the boot source for.
  2. Find out if the instance is attached to any volumes:
openstack server show <INSTANCE-UUID> |  grep volumes_attached

If no volumes are attached, then you know the instance is using a compute server drive for storage, and it is not booted from a volume. No additional steps are needed for this instance.

If any volumes are attached, then you know that the instance is using a volume for storage, but not necessarily that it is booted from a volume. Take the following additional steps:

  1. Run openstack volume show to view details about each volume attached to the instance.
  2. Scan the attachments field in the command output. 

If the device attribute in this field includes the value /dev/vda, the volume is a root disk, which indicates that the attached instance is booted from this volume. 

If no volumes show /dev/vda for the device attribute, then the attached instance is not booted from a volume.

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