Kubernetes & Cloud-Native Infrastructure Essentials (CKA Prep) Flashcards

Question 1

What is Kubernetes?

Accepted Answer

Kubernetes is an open-source container orchestration system for automating deployment, scaling, and management of containerized applications.

Question 2

What is a Pod in Kubernetes?

Accepted Answer

A Pod is the smallest deployable unit in Kubernetes, encapsulating one or more containers (e.g., Docker containers), storage resources, a unique network IP, and options that govern how the containers run.

Question 3

What is the primary role of the `kube-apiserver`?

Accepted Answer

The `kube-apiserver` exposes the Kubernetes API. It is the frontend for the Kubernetes control plane, processing REST requests, validating them, and updating the state in `etcd`.

Question 4

What is the function of `etcd` in a Kubernetes cluster?

Accepted Answer

`etcd` is a consistent and highly available key-value store used by Kubernetes to store all cluster data (e.g., cluster state, configuration, metadata). It's the single source of truth for the cluster.

Question 5

What does the `kube-scheduler` do?

Accepted Answer

The `kube-scheduler` watches for newly created Pods with no assigned node and selects an optimal node for them to run on. It considers resource requirements, hardware/software/policy constraints, affinity/anti-affinity specifications, and data locality.

Question 6

Explain the role of the `kube-controller-manager`.

Accepted Answer

The `kube-controller-manager` runs various controller processes (e.g., Node Controller, Replication Controller, Endpoints Controller, Service Account & Token Controllers). These controllers continuously monitor the cluster's shared state via the API server and make changes to move the current state towards the desired state.

Question 7

What is the `kubelet`'s responsibility on a Kubernetes node?

Accepted Answer

The `kubelet` is an agent that runs on each node in the cluster. It ensures that containers are running in a Pod according to the PodSpecs provided by the `kube-apiserver`. It registers the node with the cluster and reports its status.

Question 8

What is the purpose of `kube-proxy`?

Accepted Answer

`kube-proxy` runs on each node and maintains network rules (e.g., using `iptables` or IPVS) on the node. These rules enable network communication to your Pods from inside or outside the cluster, abstracting away the complexity of Pod networking for Services.

Question 9

What is a Kubernetes `Deployment`?

Accepted Answer

A `Deployment` is a higher-level abstraction that manages stateless applications. It provides declarative updates to Pods and `ReplicaSets`, ensuring a specified number of Pod replicas are running and enabling rolling updates and rollbacks.

Question 10

How does a `ReplicaSet` function within a `Deployment`?

Accepted Answer

A `ReplicaSet` ensures a stable set of replica Pods are running at any given time. `Deployments` manage `ReplicaSets` to achieve their desired state, creating new `ReplicaSets` for new versions and scaling down old ones during updates.

Question 11

When would you use a `DaemonSet`?

Accepted Answer

A `DaemonSet` ensures that all (or some) nodes run a copy of a Pod. It's typically used for cluster-level operations like logging agents (`fluentd`), monitoring agents (`Prometheus node-exporter`), or storage daemons that need to run on every node.

Question 12

What is a `StatefulSet` used for?

Accepted Answer

A `StatefulSet` manages stateful applications, providing stable, unique network identifiers, stable persistent storage, and ordered, graceful deployment and scaling. It's ideal for databases (e.g., MySQL, PostgreSQL) or other applications requiring stable identities and ordered operations.

Question 13

Explain the `ClusterIP` Service type.

Accepted Answer

The `ClusterIP` Service type exposes the Service on an internal IP address within the cluster. It's only reachable from within the cluster. This is the default Service type and is used for internal communication between services.

Question 14

What is a `NodePort` Service?

Accepted Answer

A `NodePort` Service exposes the Service on each Node's IP at a static port (the `NodePort`). A `ClusterIP` Service is automatically created, and the `NodePort` routes to it. It's accessible from outside the cluster via `:`.

Question 15

Describe the `LoadBalancer` Service type.

Accepted Answer

The `LoadBalancer` Service type exposes the Service externally using a cloud provider's load balancer. It automatically provisions an external IP address and routes traffic to the Service. This type requires integration with a cloud provider (e.g., AWS ELB, GCP Load Balancer).

Question 16

What is Kubernetes `Ingress`?

Accepted Answer

`Ingress` is an API object that manages external access to services in a cluster, typically HTTP/S. It provides HTTP routing, SSL termination, and name-based virtual hosting. An `Ingress` Controller (e.g., NGINX Ingress Controller) is required to fulfill the `Ingress` rules.

Question 17

What is a `PersistentVolume` (PV)?

Accepted Answer

A `PersistentVolume` (PV) is an API object representing a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned. It's a resource in the cluster, independent of Pods, and has a lifecycle independent of any individual Pod that uses it.

Question 18

What is a `PersistentVolumeClaim` (PVC)?

Accepted Answer

A `PersistentVolumeClaim` (PVC) is a request for storage by a user. It consumes PV resources. Pods request storage via PVCs, which then bind to available PVs that meet the PVC's requirements (e.g., size, access mode).

Question 19

What is a `StorageClass` and why is it used?

Accepted Answer

A `StorageClass` provides a way for administrators to describe the 'classes' of storage they offer (e.g., fast SSD, slow HDD, network storage). It enables dynamic provisioning of PVs: when a PVC requests a `StorageClass`, a PV is automatically created and bound to it, abstracting underlying storage details.

Question 20

How do you list all Pods in the current namespace?

Accepted Answer

Use the command: `kubectl get pods`

Question 21

How do you get detailed information about a specific Pod?

Accepted Answer

Use the command: `kubectl describe pod <pod-name>`

Question 22

How do you view the logs of a running container in a Pod?

Accepted Answer

For a single-container Pod: `kubectl logs ` For a multi-container Pod: `kubectl logs -c `

Question 23

How do you execute a command inside a running container?

Accepted Answer

Use the command: `kubectl exec -it -- ` Example: `kubectl exec -it my-app-pod -- bash` to open a shell inside the container.

Kubernetes & Cloud-Native Infrastructure Essentials (CKA Prep)

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