Whitelisting sysctls for containers in Kubernetes Kind

Question

I'm trying to deploy a container in a Kubernetes Kind cluster. The container I'm trying to deploy needs a couple of sysctls flags to be set.

The deployment fails with

forbidden sysctl: "kernel.msgmnb" not whitelisted

UPDATE

I have since added a cluster policy as suggested, created a role that grants usage to it and assigned the Cluster Role to the default service account:

---
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: sysctl-psp
spec:
  privileged: false  # Don't allow privileged pods!
  # The rest fills in some required fields.
  seLinux:
    rule: RunAsAny
  supplementalGroups:
    rule: RunAsAny
  runAsUser:
    rule: RunAsAny
  fsGroup:
    rule: RunAsAny
  volumes:
  - '*'
  allowedUnsafeSysctls:
  - kernel.msg*
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: role_allow_sysctl
rules:
- apiGroups: ['policy']
  resources: ['podsecuritypolicies']
  verbs:     ['*']
  resourceNames:
  - sysctl-psp
- apiGroups: ['']
  resources:
  - replicasets
  - services
  - pods
  verbs: ['*']
- apiGroups: ['apps']
  resources:
  - deployments
  verbs: ['*']

The cluster role binding is like this:

kubectl -n <namespace> create rolebinding default:role_allow_sysctl --clusterrole=role_allow_sysctl --serviceaccount=<namespace>:default

I am then trying to create a deployment and a service in the same namespace:

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: test-app
  labels:
    app: test-app
spec:
  selector:
    matchLabels:
      app: test-app
      tier: dev
  strategy:
    type: Recreate
  template:
    metadata:
      labels:
        app: test-app
        tier: dev
    spec:
      securityContext:
        sysctls:
        - name: kernel.msgmnb
          value: "6553600"
        - name: kernel.msgmax
          value: "1048800"
        - name: kernel.msgmni
          value: "32768"
        - name: kernel.sem
          value: "128 32768 128 4096"
      containers:
      - image: registry:5000/<container>:1.0.0
        name: test-app
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 10666
          name:port-1
---

The problem remains the same however, I'm getting multiple pods spawned, all failing with the same message forbidden sysctl: "kernel.msgmnb" not whitelisted

Answer 1

I don't think that --alowed-unsafe-sysctls flag could work with Kind nodes, because Kind nodes themselves are containers, whose sysctl FS is read-only.

My workaround is to change the needed sysctl values on my host machine. Kind nodes (and in turn their containers) will reuse these values.