Unable to Create Virtual Machine on Compute Host – Host Not Mapped to Any Cell

Problem

Virtual Machine creation fails with the following error:

VM Creation Logs
    
 
Host '[HOST_UUID]' is not mapped to any cell
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Environment

Self-Hosted Private Cloud Director Virtualization - v2025.4 and Higher
Self-Hosted Private Cloud Director Kubernetes - v2025.4 and Higher

For Private Cloud Director (SaaS) users, if you encounter the same issue, please contact Platform9 Support.

Cause

The compute host was not properly mapped to any Nova cell. This can happen if:

The host was added without triggering automatic cell discovery.
The host was removed or modified in a way that removed its mapping from the cell database.

Without this mapping, Nova is unable to schedule workloads on the host, even if it appears active and functional.

Diagnostics

Run the following command from the nova-scheduler pod on Management Plane to see if the host is linked to a cell:

nova-manage command
    
 
$ nova-manage cell_v2 list_hosts+--------------+--------------+---------------------+|  Cell Name   |   Cell UUID  |       Hostname      |+--------------+--------------+---------------------+| [CELL_NAME]  | [CELL_UUID]  | [HOST1.EXAMPLE.COM] || [CELL_NAME]  | [CELL_UUID]  | [HOST2.EXAMPLE.COM] |+--------------+--------------+---------------------+
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The compute service on the host still might be visible and enabled:

Openstack Command
    
$ openstack compute service list --host <HOST3.EXAMPLE.COM>+------------------------+--------------+---------------------+-----------------+---------+-------+--------------+| ID                     | Binary       | Host                | Zone            | Status  | State | Updated At   |+------------------------+--------------+---------------------+---------------------------+-------+--------------+| [COMPUTE_SERVICE_UUID] | nova-compute | [HOST3.EXAMPLE.COM] | [CLUSTER_NAME]  | enabled | up    | [TIME_STAMP] |+------------------------+--------------+--------------+------------------------+---------+-------+--------------+
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Resolution

Run the following command from nova-scheduler pod on Management Plane to find any unmapped compute hosts and create their cell mappings:

nova-manage command
    
​x
 
$ nova-manage cell_v2 discover_hosts --verbose --by-service​Found [CELL_MAPPINGS_COUNT] cell mappings.Getting computes from cell '[CELL_NAME]': [CELL_UUID]Creating host mapping for service [HOST3.EXAMPLE.COM]Found [MISSING_COMPUTES_COUNT] unmapped computes in cell: [CELL_UUID]
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Validation

Confirm the host is mapped to a cell.

nova-manage command
    
 
$ nova-manage cell_v2 list_hosts+--------------+-------------+---------------------+|  Cell Name   |  Cell UUID  |      Hostname       |+--------------+-------------+---------------------+| [CELL_NAME]  | [CELL_UUID] | [HOST1.EXAMPLE.COM] || [CELL_NAME]  | [CELL_UUID] | [HOST2.EXAMPLE.COM] || [CELL_NAME]  | [CELL_UUID] | [HOST3.EXAMPLE.COM] |+--------------+-------------+---------------------+
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Verify the compute service is active

Openstack Command
    
$ openstack compute service list --host <HOST3.EXAMPLE.COM>+------------------------+--------------+---------------------+-----------------+---------+-------+--------------+| ID                     | Binary       | Host                | Zone            | Status  | State | Updated At   |+------------------------+--------------+---------------------+---------------------------+-------+--------------+| [COMPUTE_SERVICE_UUID] | nova-compute | [HOST3.EXAMPLE.COM] | [CLUSTER_NAME]  | enabled | up    | [TIME_STAMP] |+------------------------+--------------+--------------+------------------------+---------+-------+--------------+
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Attempt to launch a virtual machine and confirm it succeeds.

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