Hi openstack CLI wizards,

Having flavors without disks, I want volumes to be created from images on the fly that I can boot from.
But I don't want to do bookkeeping for these volumes; they should disappear once the server disappears.

On the command line with nova, I can do this:
nova boot --nic net-name=$MYNET --key-name $MYKEY --flavor $MYFLAVOR \
--block-device "id=$MYIMGIFD,source=image,dest=volume,size=$MYSIZE,shutdown=remove,bootindex=0" $MYNAME

I did not find a way to do this with openstack server create.
Is there one?

Here's what I tried:
--image $MYIMGID --boot-from-volume $MYSIZE
works, except that there is no way to specify delete_on_termination

--block-device-mapping "sda=$MYIMGID:image:$MYSIZE:true"
does complain that no --image or --volume have been passed.
The option does not appear to be used for bootable volumes.

I have seen a BP (merged with Ussuri) that would allow a PUT call to update delete_on_termination, but I don't see it usable with the openstackclient ...
https://specs.openstack.org/openstack/nova-specs/specs/ussuri/implemented/destroy-instance-with-datavolume.html

Anything obvious I missed?

Thanks,