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4.6. Managing instance snapshots

You can use an instance snapshot to create a new image from an instance. This is very convenient for upgrading base images or for taking a published image and customizing it for local use.

The difference between an image that you upload directly to the Image service and an image that you create by snapshot is that an image created by snapshot has additional properties in the Image service database. These properties are in the image_properties table and include the following parameters:

表4.9 Snapshot options










Use snapshots to create new instances based on that snapshot, and potentially restore an instance to that state. You can perform this action while the instance is running.

By default, a snapshot is accessible to the users and projects that were selected while launching an instance that the snapshot is based on.

4.6.1. Creating an instance snapshot


If you intend to use an instance snapshot as a template to create new instances, you must ensure that the disk state is consistent. Before you create a snapshot, set the snapshot image metadata property os_require_quiesce=yes:

$ openstack image set --property os_require_quiesce=yes <image_id>

For this to work, the guest must have the qemu-guest-agent package installed, and the image must be created with the metadata property parameter hw_qemu_guest_agent=yes set.:

$ openstack image create \
--disk-format raw \
--container-format bare \
--file <file_name> \
--is-public True \
--property hw_qemu_guest_agent=yes \
--progress \
--name <name>

If you unconditionally enable the hw_qemu_guest_agent=yes parameter, then you are adding another device to the guest. This consumes a PCI slot, and limits the number of other devices you can allocate to the guest. It also causes Windows guests to display a warning message about an unknown hardware device.

For these reasons, setting the hw_qemu_guest_agent=yes parameter is optional, and you must use the parameter only for images that require the QEMU guest agent.

  1. In the dashboard, select Project > Compute > Instances.
  2. Select the instance from which you want to create a snapshot.
  3. In the Actions column, click Create Snapshot.
  4. In the Create Snapshot dialog, enter a name for the snapshot and click Create Snapshot.

    The Images category now shows the instance snapshot.

To launch an instance from a snapshot, select the snapshot and click Launch.