Open Stack

My virtual machine created, often in the absence of intervention into the
stopped state:

pyw at ven-1:~/devstack$ virsh list --all
 Id Name                 State
----------------------------------
  - instance-00000040    shut off
  - instance-00000044    shut off
  - instance-00000045    shut off
  - instance-00000046    shut off
  - instance-00000047    shut off
  - instance-0000005b    shut off
  - instance-0000005e    shut off
  - instance-00000065    shut off
  - instance-0000006e    shut off
  - instance-00000075    shut off
  - instance-00000076    shut off
  - instance-00000077    shut off
  - instance-0000007c    shut off
  - instance-0000007d    shut off
  - instance-00000081    shut off
  - instance-00000082    shut off
  - instance-00000083    shut off
  - instance-00000084    shut off
  - instance-00000085    shut off

query the nova the database, you can see:
vm_state: stopped
Why is this?
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