Kubernetes - Core Concepts & Deployment Flashcards

Question 1

What is Kubernetes?

Accepted Answer

An open-source container orchestration system for automating deployment, scaling, and management of containerized applications. It groups containers into logical units for easy management and discovery, abstracting away the underlying infrastructure.

Question 2

What is a Pod in Kubernetes?

Accepted Answer

The smallest deployable unit in Kubernetes. A `Pod` encapsulates one or more co-located containers (e.g., Docker containers), shared storage resources, a unique network IP, and options that govern how the containers run. All containers in a `Pod` share the same network namespace and can communicate via `localhost`.

Question 3

What is a Node in Kubernetes?

Accepted Answer

A `Node` is a worker machine (physical or virtual) in a Kubernetes cluster. Each `Node` runs `Pods` and is managed by the Kubernetes control plane. It contains the necessary services to run `Pods`, including a container runtime (e.g., containerd), `kubelet` (an agent for the master), and `kube-proxy`.

Question 4

What is a Kubernetes Cluster?

Accepted Answer

A set of nodes that run containerized applications. A cluster consists of at least one master node (control plane) and multiple worker nodes. The control plane manages the worker nodes and the `Pods` in the cluster, handling tasks like scheduling, scaling, and updates.

Question 5

What is `kubectl`?

Accepted Answer

The command-line tool for interacting with a Kubernetes cluster. `kubectl` allows you to run commands against Kubernetes clusters, deploying applications, inspecting and managing cluster resources, and viewing logs.

Question 6

Explain Kubernetes Namespaces.

Accepted Answer

`Namespaces` provide a mechanism for isolating groups of resources within a single Kubernetes cluster. They are used to divide cluster resources among multiple users or teams, providing scope for names and preventing naming collisions. Resources within different `Namespaces` are logically separated.

Question 7

What is a ReplicaSet?

Accepted Answer

A `ReplicaSet` ensures that a specified number of `Pod` replicas are running at any given time. Its primary purpose is to maintain the stability of a set of `Pods`. `Deployments` are higher-level concepts that manage `ReplicaSets` and provide declarative updates to `Pods`.

Question 8

What is a Deployment in Kubernetes?

Accepted Answer

A `Deployment` provides declarative updates for `Pods` and `ReplicaSets`. You describe a desired state in a `Deployment` object, and the `Deployment` Controller changes the actual state to the desired state at a controlled rate. It's commonly used for stateless applications and supports features like rolling updates and rollbacks.

Question 9

Provide a basic YAML structure for a Kubernetes Pod.

Accepted Answer

```yaml
apiVersion: v1
kind: Pod
metadata:
  name: my-nginx-pod
  labels:
    app: nginx
spec:
  containers:
  - name: nginx
    image: nginx:latest
    ports:
    - containerPort: 80
```

Question 10

Provide a basic YAML structure for a Kubernetes Deployment.

Accepted Answer

```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-app-container
        image: my-app-image:v1.0
        ports:
        - containerPort: 8080
```

Question 11

What is a Service in Kubernetes?

Accepted Answer

A `Service` is an abstract way to expose an application running on a set of `Pods` as a network service. It provides a stable IP address and DNS name for a group of `Pods`, abstracting away the ephemeral nature of `Pods`. Common types include `ClusterIP`, `NodePort`, and `LoadBalancer`.

Question 12

Explain the different types of Kubernetes Services.

Accepted Answer

* `ClusterIP`: Exposes the `Service` on an internal IP in the cluster. Only reachable from within the cluster. Default type. * `NodePort`: Exposes the `Service` on a static port on each `Node`'s IP. Makes the `Service` accessible from outside the cluster using `:`. * `LoadBalancer`: Exposes the `Service` externally using a cloud provider's load balancer. Only works with cloud providers that support external load balancers. * `ExternalName`: Maps the `Service` to the contents of the `externalName` field (e.g., `foo.bar.example.com`) by returning a `CNAME` record. No proxying involved.

Question 13

Provide a basic YAML structure for a Kubernetes Service (ClusterIP).

Accepted Answer

```yaml
apiVersion: v1
kind: Service
metadata:
  name: my-app-service
spec:
  selector:
    app: my-app # Selects Pods with this label
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080 # Port on the Pod
  type: ClusterIP
```

Question 14

What is a StatefulSet?

Accepted Answer

A `StatefulSet` is a workload API object used to manage stateful applications. It provides guarantees about the ordering and uniqueness of `Pods`, stable network identities, and stable persistent storage. Ideal for databases, message queues, and other stateful applications where `Pod` identity and order matter.

Question 15

What is a DaemonSet?

Accepted Answer

A `DaemonSet` ensures that all (or some) `Nodes` run a copy of a `Pod`. As `Nodes` are added to the cluster, new `Pods` are automatically added to them. As `Nodes` are removed, those `Pods` are garbage collected. Useful for cluster-level operations like logging agents, monitoring agents, or storage daemons.

Question 16

What is a ConfigMap?

Accepted Answer

A `ConfigMap` is an API object used to store non-confidential data in key-value pairs. It allows you to decouple configuration artifacts from image content to keep containerized applications portable. `ConfigMaps` can be consumed by `Pods` as environment variables, command-line arguments, or as files in a volume.

Question 17

Provide a basic YAML structure for a Kubernetes ConfigMap.

Accepted Answer

```yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  database.host: "mysql-service"
  api.endpoint: "/api/v1"
  log.level: "INFO"
```

Question 18

Explain Rolling Updates in Kubernetes Deployments.

Accepted Answer

`Rolling Updates` allow `Deployment` updates to take place with zero downtime by incrementally updating `Pod` instances with new ones. New `Pods` are created with the updated configuration, and old `Pods` are terminated only after the new `Pods` are ready, ensuring continuous availability and allowing for easy rollbacks.

Question 19

What are Liveness and Readiness Probes in Kubernetes?

Accepted Answer

*   **Liveness Probe**: Determines if a container is running. If it fails, Kubernetes restarts the container. Ensures long-running applications are healthy and can recover from deadlocks.
*   **Readiness Probe**: Determines if a container is ready to serve requests. If it fails, the `Pod` is removed from `Service` endpoints until it becomes ready. Prevents traffic from being sent to unready `Pods` during startup or temporary issues.

Question 20

What is a PersistentVolume (PV)?

Accepted Answer

A `PersistentVolume` (PV) is a piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using Storage Classes. It's a resource in the cluster, independent of `Pods`, and represents actual storage capacity (e.g., NFS, iSCSI, cloud-specific storage).

Question 21

What is a PersistentVolumeClaim (PVC)?

Accepted Answer

A `PersistentVolumeClaim` (PVC) is a request for storage by a user. It's a request for a `PV` resource, specifying size, access modes (e.g., ReadWriteOnce, ReadOnlyMany), and storage class. `Pods` then use `PVCs` to consume `PV` resources, abstracting the details of the underlying storage.

Question 22

List common `kubectl` commands for managing resources.

Accepted Answer

* `kubectl get `: List resources (e.g., `kubectl get pods`, `kubectl get deployments`). * `kubectl describe /`: Show detailed information about a specific resource. * `kubectl apply -f `: Apply a configuration from a file. * `kubectl delete -f ` or `kubectl delete /`: Delete resources. * `kubectl logs `: Print the logs for a container in a `Pod`. * `kubectl exec -it -- `: Execute a command in a container within a `Pod`. * `kubectl scale deployment/ --replicas=`: Scale a `Deployment` to a desired number of replicas.

Kubernetes - Core Concepts & Deployment

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