How can I apply limit range to all namespaces in kubernetes - kubernetes

Question

How can I apply this file to all namespaces:
apiVersion: v1
kind: LimitRange
metadata:
name: resource-limits
spec:
limits:
-
type: Pod
max:
cpu: 1000m
memory: 1Gi
min:
cpu: 500m
memory: 500Mi
By default it gets applied to namespace I am into. I want to make this setting a common one
How can I do that. Make this a global setting.

Answer 1

This can be very easily done using an admission controller like Kyverno. Kyverno has "generate" capability which can be used to generate any Kubernetes resource based on a trigger (e.g. create namespace)
Here is an example of a Kyverno policy to achieve this.
https://kyverno.io/policies/best-practices/add_ns_quota/add_ns_quota/
apiVersion: kyverno.io/v1
kind: ClusterPolicy
metadata:
name: add-ns-quota
annotations:
policies.kyverno.io/title: Add Quota
policies.kyverno.io/category: Multi-Tenancy
policies.kyverno.io/subject: ResourceQuota, LimitRange
policies.kyverno.io/description: >-
To better control the number of resources that can be created in a given
Namespace and provide default resource consumption limits for Pods,
ResourceQuota and LimitRange resources are recommended.
This policy will generate ResourceQuota and LimitRange resources when
a new Namespace is created.
spec:
rules:
- name: generate-resourcequota
match:
resources:
kinds:
- Namespace
generate:
apiVersion: v1
kind: ResourceQuota
name: default-resourcequota
synchronize: true
namespace: "{{request.object.metadata.name}}"
data:
spec:
hard:
requests.cpu: '4'
requests.memory: '16Gi'
limits.cpu: '4'
limits.memory: '16Gi'
- name: generate-limitrange
match:
resources:
kinds:
- Namespace
generate:
apiVersion: v1
kind: LimitRange
name: default-limitrange
synchronize: true
namespace: "{{request.object.metadata.name}}"
data:
spec:
limits:
- default:
cpu: 500m
memory: 1Gi
defaultRequest:
cpu: 200m
memory: 256Mi
type: Container

Answer 2

As per my investigation, this is not possible natively in the manifest file, but here I implemented a trick-script to do so using bash, if you are deploying the manifest using kubectl, then use this auxiliary script:
#!/bin/bash
namespaces=$(echo `kubectl get namespaces -o=jsonpath='{range.items[*]} {.metadata.name}{end}'`)
for ns in $namespaces; do kubectl apply -f path-to-manifest-file.yaml --namespace $ns; done
Maybe you'd say why I'm applying this in a loop and not in one line by adding as many --namespace flags as the namespaces we have! Actually, I tried so, but it looks like kubectl command does not consider multiple --namespace when passed via a variable, like follows:
(base)
╰─$ namespace_flags=`kubectl get namespaces -o=jsonpath='{range.items[*]} --namespace {.metadata.name}{end}'`
╰─$ echo $namespace_flags
--namespace default--namespace kube-node-lease--namespace kube-public--namespace kube-system--namespace newrelic
(base)
╰─$ kubectl get pods ${namespace_flags[#]}
Error from server (NotFound): pods " --namespace default --namespace kube-node-lease --namespace kube-public --namespace kube-system --namespace newrelic" not found

Answer 3

After doing a lot of research, I got a better solution, Kyverno which is adopted as CNCF Incubating project maturity level. It can implement cluster level policies which suffices my usecase. Link is here :
https://kyverno.io/