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Enable Kubernetes audit log collection on a k3s cluster by creating the audit policy and webhook configuration files, configuring k3s to use them, and restarting the service.

Important
Important
k3s runs kube-apiserver as a host process before CoreDNS starts, so it cannot resolve Kubernetes service DNS names. The audit collector must use hostNetwork: true and connect through 127.0.0.1.

Procedure

  1. Create the audit configuration directory and files.
    Run the following commands to create the audit policy and webhook configuration:
    sudo mkdir -p /var/lib/rancher/k3s/server/audit

sudo tee /var/lib/rancher/k3s/server/audit/audit-policy.yaml << 'EOF'
apiVersion: audit.k8s.io/v1
kind: Policy
rules:
  - level: Metadata
    verbs: ["create"]
    resources:
      - group: "authorization.k8s.io"
        resources: ["subjectaccessreviews", "selfsubjectaccessreviews", "localsubjectaccessreviews"]
  - level: RequestResponse
    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
    resources:
      - group: "rbac.authorization.k8s.io"
        resources: ["roles", "rolebindings", "clusterroles", "clusterrolebindings"]
  - level: Metadata
    verbs: ["create", "update", "delete"]
    resources:
      - group: ""
        resources: ["serviceaccounts"]
  - level: None
EOF

sudo tee /var/lib/rancher/k3s/server/audit/audit-webhook-config.yaml << 'EOF'
apiVersion: v1
kind: Config
clusters:
- name: audit-collector
  cluster:
    server: http://127.0.0.1:8030/k8s-audit
contexts:
- context:
    cluster: audit-collector
    user: ""
  name: default-context
current-context: default-context
preferences: {}
users: []
EOF
  2. Configure k3s to use the audit policy and webhook.
    Edit or create /etc/rancher/k3s/config.yaml:
    kube-apiserver-arg:
  - "audit-policy-file=/var/lib/rancher/k3s/server/audit/audit-policy.yaml"
  - "audit-webhook-config-file=/var/lib/rancher/k3s/server/audit/audit-webhook-config.yaml"
  - "audit-webhook-batch-max-size=1"
  3. Restart k3s to apply the changes.
    sudo systemctl daemon-reload
sudo systemctl restart k3s
  4. Verify the configuration.
    sudo systemctl status k3s
sudo journalctl -u k3s | grep -i audit