docs: add Kubernetes CKS study notes

kubernetes/level 1/task-2.md

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+# Assignment
+
+The Nautilus DevOps team is delving into Kubernetes for app management. One team member needs to create a deployment following these details:
+
+
+Create a deployment named httpd to deploy the application httpd using the image httpd:latest (ensure to specify the tag)
+
+Note: The kubectl utility on the jump-host has been configured to work with the Kubernetes cluster.
+
+# Solution
+
+# Kubernetes Deployment — `httpd`
+
+A Deployment named `httpd` running the `httpd:latest` image. Applied inline via a
+heredoc — no manifest file on disk.
+
+## Apply (heredoc → kubectl)
+
+```bash
+kubectl apply -f - <<'EOF'
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: httpd
+  labels:
+    app: httpd
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: httpd
+  template:
+    metadata:
+      labels:
+        app: httpd
+    spec:
+      containers:
+        - name: httpd
+          image: httpd:latest
+EOF
+```
+
+## How it works
+
+### The heredoc apply pattern
+
+- **`kubectl apply -f -`** reads the manifest from **stdin**; the heredoc feeds the YAML
+  straight in, so nothing is written to disk.
+- **`<<'EOF'` (delimiter quoted)** disables shell expansion inside the body, so any
+  `$VAR` / backticks in a manifest stay literal — the right default for Kubernetes YAML.
+- **Indentation matters** — keep it exact, spaces not tabs.
+
+### The manifest, field by field
+
+- **`apiVersion: apps/v1` / `kind: Deployment`** — a Deployment is an `apps/v1` object
+  that manages a ReplicaSet, which in turn manages Pods. It gives you declarative
+  updates, rollouts/rollbacks, and self-healing (recreates pods that die).
+- **`metadata.name: httpd`** — the Deployment's name, exactly as required.
+- **`spec.replicas: 1`** — how many pod copies to run. The task doesn't specify a
+  count, so one replica is the minimal correct choice.
+- **`spec.selector.matchLabels.app: httpd`** — how the Deployment finds the pods it
+  owns. This **must** match the pod template's labels below, or the API rejects the
+  manifest (`selector does not match template labels`).
+- **`spec.template`** — the pod blueprint the Deployment stamps out:
+  - **`template.metadata.labels.app: httpd`** — labels applied to each pod; these are
+    what the selector targets. The label key/value is arbitrary but must be consistent
+    between selector and template.
+  - **`template.spec.containers`** — one container:
+    - **`name: httpd`** — container name.
+    - **`image: httpd:latest`** — the Apache HTTP Server image at the `latest` tag,
+      stated explicitly as required. (Bare `httpd` defaults to `latest`, but the task
+      asks for the tag to be specified.)
+
+### Why the selector/template labels must agree
+
+A Deployment is decoupled from its pods — it tracks them purely by label selector.
+`spec.selector.matchLabels` is the query; `spec.template.metadata.labels` is what gets
+stamped on each pod. If they don't match, the Deployment couldn't recognize its own
+pods, so Kubernetes rejects the config outright. Keeping both `app: httpd` satisfies
+that contract.
+
+## Verify
+
+```bash
+# Deployment exists and is available
+kubectl get deployment httpd
+
+# Rollout completed
+kubectl rollout status deployment/httpd
+
+# Pod is running with the right image
+kubectl get pods -l app=httpd \
+  -o jsonpath='{.items[0].spec.containers[0].image}{"\n"}'
+```
+
+Expected — `httpd` deployment showing `READY 1/1`, rollout reporting success, and the
+image printing `httpd:latest`.
+
+> If a pod sits in `ImagePullBackOff`, the node may be offline or rate-limited on the
+> pull. `kubectl describe pod <name>` shows pull events under `Events:`.