The default namespace comes with a LimitRange that assigns a default CPU and memory request to pods that do not define one explicitly. We enabled this feature to try and prevent people from breaking their clusters. The default request is enforced if a container is created in the default namespace, and the container does not specify its own values for memory and CPU requests. The container is then given a default memory request of 100MiB and a default CPU request of 100Mi which is 100 millicpus. You can view the limit ranges with:

kubectl get limitranges

We only enforce the default requests in the default namespace. You can find additional information about requests, limits and quotas for memory resources and CPU resources in the kubernetes documentation.

Default LimitRange:

apiVersion: v1
kind: LimitRange
  name: default-limit-range
  namespace: default
  - defaultRequest:
      cpu: 100m
      memory: 100Mi
    type: Container