While traditional infrastructure makes a clear distinction between images (OS templates) and snapshots (point-in-time volume states), OpenStack blurs this line for operational flexibility. The core differentiation lies in metadata properties and use case optimization:

# Glance image-show output comparison
# Standard image properties
glance image-show standard_image
| Property         | Value           |
|------------------|-----------------|
| disk_format      | qcow2           |
| container_format | bare            |

# Snapshot-derived image properties  
glance image-show snapshot_image
| Property              | Value                 |
|-----------------------|-----------------------|
| snapshot_id           | a1b2c3d4              |
| instance_uuid         | e5f6g7h8              |
| base_image_ref        | i9j0k1l2              |

OpenStack's design serves two primary technical needs:

• Instance Portability: Snapshots maintain VM-specific configurations (nova boot --image snapshot_image preserves networking/IP settings)
• Template Customization: Standard images support cloud-init injection during launch (cloud_config gets processed only on first boot)

Consider this Nova API sequence for creating a golden image:

# Create instance from base image
nova boot --image cirros --flavor 1 test_vm

# Create snapshot (becomes Glance image)
nova image-create test_vm vm_snapshot

# Convert to reusable template
glance image-update vm_snapshot \
  --property image_type=golden \
  --remove-property instance_uuid

Snapshot-backed images exhibit different storage behavior:

This Python snippet demonstrates snapshot lineage tracking:

from glanceclient import Client

gc = Client('2', session=keystone_session)

def get_image_lineage(image_id):
    lineage = []
    while True:
        img = gc.images.get(image_id)
        lineage.append(img.name)
        if not hasattr(img, 'base_image_ref'):
            break
        image_id = img.base_image_ref
    return lineage

OpenStack treats images and snapshots as fundamentally different entities despite their technical similarities in the Glance database. Here's why:

# Example: Creating an image from snapshot in OpenStack CLI
openstack image create --disk-format qcow2 --container-format bare \
--property image_type='snapshot' snapshot_from_instance

While both appear as Glance images, snapshots carry critical metadata:

# Sample API response showing snapshot-specific properties
{
  "image": {
    "id": "c6a3a7d0-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
    "name": "prod-server-snapshot",
    "properties": {
      "image_type": "snapshot",
      "instance_uuid": "a1b2c3d4-xxxx-xxxx-xxxx-xxxxxxxxxxxx",
      "base_image_ref": "67890abc-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
    }
  }
}

Three technical reasons for maintaining separation:

1. Lifecycle Management: Snapshots maintain instance relationships for rollback scenarios
2. Storage Optimization: Images use copy-on-write while snapshots preserve exact block states
3. API Behavior: Certain operations (e.g., shelving) automatically generate snapshots

Here's how to properly convert between types:

# Convert snapshot to deployable image
openstack image create --disk-format qcow2 \
--property image_type='image' \
--file snapshot.qcow2 deployable_image

# Verify conversion succeeded
openstack image show deployable_image -f json | jq '.properties.image_type'

• Attempting to launch instances directly from large snapshots
• Assuming snapshot metadata persists through image conversions
• Neglecting to clean up orphaned snapshot-derived images

# Recommended snapshot retention policy
openstack image list --property image_type=snapshot \
--sort-column Created_at --limit 5 -f value -c ID | \
xargs -n1 openstack image delete