Docker &amp; Kubernetes

Alerting on under-replicated Deployments

Write an alerting rule comparing kube_state_metrics available vs desired replicas with for: 5m, Prometheus evaluates and fires to Alertmanager, which dedupes/routes/notifies.

PromQL for top 5 CPU-consuming pods

Apply rate() to the counter over 15m, sum by pod to combine containers, then wrap in topk(5); rate handles counter resets.

EFK centralized logging architecture

Fluentd runs as a DaemonSet collecting node container logs, parses and forwards to Elasticsearch for indexed storage, and Kibana queries and visualizes them.

Auto-discovering app pods for Prometheus scraping

Use kubernetes_sd_configs with role pod, relabel on pod annotations like prometheus.io/scrape to filter, and set path and port; with the Operator use a PodMonitor or ServiceMonitor.

kube-state-metrics versus node-exporter

Kube-state-metrics exposes API object state (deployment replicas, pod phase, restarts) from the control plane, while node-exporter exposes OS-level hardware metrics (CPU, memory, disk) per…

Viewing pod logs and durable log collection

Kubectl logs (with -c, --previous, -f) reads container stdout/stderr; because that storage is ephemeral, run a node-level logging agent as a DaemonSet shipping logs to a central store.

Multi-tenant isolation with a monitoring exception

Apply default-deny ingress per tenant namespace, allow same-namespace traffic, then add an ingress rule permitting the monitoring namespace via namespaceSelector on the metrics port.

Binding a ClusterRole with a RoleBinding

A RoleBinding referencing a ClusterRole grants those rules only within the binding's namespace; reuse built-in roles like view per-team without duplicating definitions.

Root and NET_ADMIN under Pod Security Standards

Set runAsUser 0 and capabilities add NET_ADMIN in the container securityContext; this is rejected by Restricted and Baseline, so the namespace must use the Privileged profile.

Write a frontend-to-backend NetworkPolicy

Set podSelector to app=backend, policyTypes Ingress, one ingress rule with from podSelector app=frontend and ports TCP 8080; the implicit deny handles the rest.

Namespace-scoped RBAC for a ServiceAccount

Create a Role in production granting create on deployments (apps group) and services (core group), then a RoleBinding tying that Role to the ServiceAccount.

Troubleshooting an RBAC forbidden error

Use kubectl auth can-i with --as impersonation to check the verb, inspect RoleBindings and ClusterRoleBindings, and read the role rules.

First NetworkPolicy flips a pod to default-deny

Once any policy selects a pod for a direction, that direction becomes default-deny and only explicitly allowed traffic passes; unselected pods stay open.

Role versus ClusterRole in RBAC

Role is namespaced, ClusterRole is cluster-wide and covers cluster-scoped resources, and you grant either via a RoleBinding (namespaced) or ClusterRoleBinding (cluster-wide) to a subject.

Topology spread constraints versus pod anti-affinity

Spread constraints balance pod counts per domain bounded by maxSkew, anti-affinity is all-or-nothing co-location avoidance, and maxSkew caps the difference between fullest and emptiest…

tolerationSeconds and graceful eviction on NoExecute

TolerationSeconds is how long a tolerating pod may stay after the taint applies; once it elapses eviction starts, then terminationGracePeriodSeconds governs the SIGTERM-to-SIGKILL window.

Pinning exclusive CPU cores to a pod

Set kubelet CPU Manager policy to static, make the pod Guaranteed QoS with integer CPU limits equal to requests, so it gets exclusive dedicated cores.

Taints and tolerations versus node affinity

Taints repel pods from nodes (reserve hardware), affinity attracts pods to nodes, and you combine both so only tolerating pods land AND only those pods seek the node.

Spreading replicas across availability zones

Use topologySpreadConstraints on topology.kubernetes.io/zone with a small maxSkew, choose DoNotSchedule or ScheduleAnyway, and confirm nodes carry zone labels.