Kubernetes & Cloud-Native Infrastructure Essentials Flashcards

Question 1

Pod

Accepted Answer

The smallest deployable unit in Kubernetes, representing a single instance of a running process. A Pod contains one or more co-located containers that share storage resources, a network IP, and container port specs.

Question 2

Deployment

Accepted Answer

A declarative Kubernetes workload resource that manages stateless application Pods. It automatically manages `ReplicaSets` to handle declarative updates, scaling, rollouts, and zero-downtime rollbacks.

Question 3

ReplicaSet

Accepted Answer

A background controller that maintains a stable set of replica Pods running at any given time. It guarantees the availability of a specified number of identical Pod instances.

Question 4

StatefulSet

Accepted Answer

A workload resource used to manage stateful applications (e.g., databases like PostgreSQL or Kafka). Unlike Deployments, it provides unique network identifiers, persistent storage bindings per Pod, and ordered deployment and termination.

Question 5

DaemonSet

Accepted Answer

A controller that ensures a copy of a specific Pod runs on all (or selected) nodes in the cluster. Commonly used for cluster-wide infrastructure agents like log collectors (`Fluentd`) and monitoring agents (`Prometheus Node Exporter`).

Question 6

ClusterIP Service

Accepted Answer

The default Kubernetes Service type. It assigns an internal, stable cluster-only IP address to route traffic to a set of matching Pods, making them accessible only from within the cluster.

Question 7

NodePort Service

Accepted Answer

A Service type that exposes the application on a static port (range `30000-32767`) on every cluster Node's IP address. It automatically routes external node traffic to an underlying `ClusterIP` Service.

Question 8

LoadBalancer Service

Accepted Answer

A Service type that integrates with the underlying cloud provider (e.g., AWS, GCP, Azure) to provision an external network load balancer, routing public traffic directly to cluster nodes.

Question 9

Ingress & Ingress Controller

Accepted Answer

An **Ingress** is an API object that defines Layer 7 HTTP/HTTPS routing rules (hostnames, paths, SSL termination) for external traffic. An **Ingress Controller** (e.g., NGINX Ingress) is the reverse-proxy daemon that implements those rules.

Question 10

ConfigMap

Accepted Answer

An API object used to store non-sensitive configuration data in key-value pairs. Consumed by Pods as environment variables, command-line arguments, or mounted configuration files in a volume.

Question 11

Secret

Accepted Answer

An API object meant to store sensitive data like passwords, TLS certificates, and API tokens. By default, keys are base64-encoded and can be injected into Pods via environment variables or mounted filesystems.

Question 12

PersistentVolume (PV) vs. PersistentVolumeClaim (PVC)

Accepted Answer

- **PersistentVolume (PV)**: A piece of cluster storage provisioned manually by an admin or dynamically via a `StorageClass`.
- **PersistentVolumeClaim (PVC)**: A request for storage by a user/Pod that binds to a matching PV based on size and access modes.

Question 13

StorageClass

Accepted Answer

An API resource that describes the "class" or performance tier of storage (e.g., fast SSD vs. standard HDD) and enables dynamic provisioning of `PersistentVolumes` upon request by a `PersistentVolumeClaim`.

Question 14

RBAC (Role-Based Access Control)

Accepted Answer

An authorization framework in Kubernetes regulating access to API resources based on roles.
- `Role` / `ClusterRole`: Defines allowed API operations (e.g., `get`, `list`, `create`).
- `RoleBinding` / `ClusterRoleBinding`: Grants defined roles to users, groups, or ServiceAccounts.

Question 15

ServiceAccount

Accepted Answer

An identity created inside Kubernetes that provides a process running within a Pod with an authenticated identity to interact securely with the Kubernetes API server.

Question 16

Troubleshooting: `kubectl describe pod <pod-name>`

Accepted Answer

A vital CLI command that provides detailed metadata, node placement, current container status, resource limits, and recent lifecycle events (e.g., failure events, image pull errors).

Question 17

Troubleshooting: `kubectl logs` Usage

Accepted Answer

Retrieves stdout/stderr output from containers for debugging: - Single container: `kubectl logs ` - Multi-container Pod: `kubectl logs -c ` - Stream live logs: `kubectl logs -f `

Question 18

Troubleshooting: `kubectl exec` Usage

Accepted Answer

Executes a command directly inside a running container. Commonly used to start an interactive shell session for live debugging:
`kubectl exec -it <pod-name> -- /bin/sh`

Question 19

Pod States: `CrashLoopBackOff` vs `ImagePullBackOff`

Accepted Answer

- **`CrashLoopBackOff`**: The container starts, crashes immediately, and Kubernetes retries execution with exponential backoff delays.
- **`ImagePullBackOff`**: Kubernetes cannot retrieve the container image due to an invalid image name, wrong tag, or missing private registry credentials (`imagePullSecrets`).

Question 20

Liveness vs. Readiness vs. Startup Probes

Accepted Answer

- **Liveness Probe**: Checks if the container is alive; restarts the container if the check fails.
- **Readiness Probe**: Checks if the application can serve traffic; removes the Pod from Service endpoints if it fails.
- **Startup Probe**: Disables liveness/readiness checks until the application finishes initial boot tasks.

Kubernetes & Cloud-Native Infrastructure Essentials

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