Hey Sascha,

I ran into this issue too and was quite puzzled. There is this open PR which suggests that group snapshot exports are unsupported as of now: https://github.com/ceph/ceph/pull/40808

The best thing I could figure out to get consistent snapshots with multiple rbd's is to fsfreeze my filesystems (using libvirt, so domfs{freeze,thaw} in my case) and make individual snapshots of the rbd images.

Kind regards
Matthias

On 3/5/26 15:46, Sascha Lucas via ceph-users wrote:
Hi,

I created a rbd group to snap multiple images consistent regarding point in time:

# rbd group image ls vm1010
rbd/5c6acb6f-a6ea-49f4-b709-ca10d423ad42.rbd.disk1
rbd/770e7d64-128a-4e85-9906-b49332b0df26.rbd.disk0

# rbd group snap ls vm1010
ID              NAME    STATE
4c8d35cc0d0177  snap-1  complete

But how do I export/export diff a group snap? The individual images show no snaps:

# rbd group snap info vm1010@snap-1
rbd group snapshot 'snap-1':
     id: 4c8d35cc0d0177
     state: complete
     image snap: .group.1_18efdc6b8b4567_4c8d35cc0d0177
     images:
         rbd/5c6acb6f-a6ea-49f4-b709-ca10d423ad42.rbd.disk1 (snap id: 202)
         rbd/770e7d64-128a-4e85-9906-b49332b0df26.rbd.disk0 (snap id: 203)

# rbd info rbd/5c6acb6f-a6ea-49f4-b709-ca10d423ad42.rbd.disk1
rbd image '5c6acb6f-a6ea-49f4-b709-ca10d423ad42.rbd.disk1':
     size 22 GiB in 5632 objects
     order 22 (4 MiB objects)
     snapshot_count: 1
     id: 18efd69508379e
     block_name_prefix: rbd_data.18efd69508379e
     format: 2
    features: layering, exclusive-lock, object-map, fast-diff, deep- flatten, operations
     op_features: group
     flags:
     group: rbd/vm1010
     create_timestamp: Tue Nov 15 12:59:56 2022
     access_timestamp: Thu Mar  5 13:59:29 2026
     modify_timestamp: Thu Mar  5 14:00:06 2026


# rbd snap ls rbd/5c6acb6f-a6ea-49f4-b709-ca10d423ad42.rbd.disk1
<no output>

Ceph version is v20.2.0 with cephadm.

TIA, Sascha.
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