FIELD NOTE / INSTAGRAM
A namespace is not a tenant security boundary by itself.
The complete written thought and the evidence behind it. The video edition will follow its public release.
The written argument is here.
This approved Instagram edition is on the journal now. Its video player and original platform link will appear after each public release is verified.
A namespace is not a tenant security boundary by itself.
Day 27 · Week 4 editorial group · Instagram · no publication date or time assigned
Video caption
A namespace is not a tenant security boundary by itself.
The CNI may not enforce the NetworkPolicy object.
Use disposable identities and harmless denial cases.
Name the enforced boundary and its limits.
#EricFieldNotes
Full written post / accessibility read
Kubernetes namespaces organize API resources. They do not automatically give a tenant least-privilege RBAC, a working deny-by-default network policy or compute isolation. A time-sliced GPU also lacks MIG's memory and fault isolation.
Picture two customer namespaces with a deny policy. If the installed network plugin does not implement it, packets may still flow. A dashboard that lists the policy is evidence of configuration, not of a blocked cross-tenant path.
From Tenant A, attempt a forbidden API read and an ordinary network connection to Tenant B in a test cluster. Verify denial outside the initiating session. Run shared-GPU interference tests for the offered mechanism. Keep the namespace, service account, CNI and device-sharing mode with the result.
Use separate nodes or stronger virtualization when the customer's risk requires it; use shared modes only with explicit terms and tests. Do this because a YAML namespace and a GPU replica are labels unless the data and control paths reject the forbidden action.
#EricFieldNotes
Four-beat scene transcript
1. A namespace is not a tenant security boundary by itself.
Kubernetes namespaces organize API resources. They do not automatically give a tenant least-privilege RBAC, a working deny-by-default network policy or compute isolation. A time-sliced GPU also lacks MIG's memory and fault isolation.
Visual: Sharing GPUs also shares a cluster and its mistakes.
2. A policy file can be present and ineffective.
Picture two customer namespaces with a deny policy. If the installed network plugin does not implement it, packets may still flow. A dashboard that lists the policy is evidence of configuration, not of a blocked cross-tenant path.
Visual: The CNI may not enforce the NetworkPolicy object.
3. Probe each tenant boundary separately.
From Tenant A, attempt a forbidden API read and an ordinary network connection to Tenant B in a test cluster. Verify denial outside the initiating session. Run shared-GPU interference tests for the offered mechanism. Keep the namespace, service account, CNI and device-sharing mode with the result.
Visual: Use disposable identities and harmless denial cases.
4. Sell an isolation class you can demonstrate.
Use separate nodes or stronger virtualization when the customer's risk requires it; use shared modes only with explicit terms and tests. Do this because a YAML namespace and a GPU replica are labels unless the data and control paths reject the forbidden action.
Visual: Name the enforced boundary and its limits.
Research and claim limits
- Kubernetes multi-tenancy guidance (S190)
- NVIDIA GPU time-slicing (S184)
The examples identified as illustrative or simulated are design probes, not reported incidents. Vendor specifications do not establish workload performance.