Kubernetes - Container Orchestration, Pods & Deployments Flashcards

Question 1

What is Kubernetes?

Accepted Answer

Kubernetes (K8s) is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It groups containers that make up an application into logical units for easy management and discovery.

Question 2

What is Container Orchestration?

Accepted Answer

Container orchestration is the automated management of containerized applications, including tasks like deployment, scaling, networking, load balancing, and availability. Kubernetes is the leading tool for this.

Question 3

What is `kubectl`?

Accepted Answer

`kubectl` is the command-line tool for running commands against Kubernetes clusters. It allows you to deploy applications, inspect and manage cluster resources, and view logs.

Question 4

What is a Pod in Kubernetes?

Accepted Answer

A Pod is the smallest deployable unit in Kubernetes. It represents a single instance of a running process in your cluster. A Pod typically contains one or more containers (e.g., Docker containers) that share storage, network, and a specification for how to run them.

Question 5

Why do Pods exist instead of just running containers directly?

Accepted Answer

Pods provide a higher level of abstraction than individual containers. They enable co-located containers to share resources (network, storage) and communicate easily. Pods also provide a stable environment for containers, allowing Kubernetes to manage their lifecycle, health checks, and restart policies.

Question 6

Provide a basic YAML structure for a Kubernetes Pod.

Accepted Answer

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

Question 7

What is a Deployment in Kubernetes?

Accepted Answer

A Deployment is a higher-level abstraction that manages the desired state for a set of identical Pods. It ensures that a specified number of Pod replicas are running at all times and provides declarative updates for Pods and ReplicaSets.

Question 8

How does a Deployment manage Pods?

Accepted Answer

A Deployment uses a `ReplicaSet` to manage its Pods. When you create a Deployment, it creates a `ReplicaSet` which then creates the specified number of Pods. When you update a Deployment, it creates a new `ReplicaSet` with the new configuration, gradually scales down the old `ReplicaSet`, and scales up the new one, ensuring zero downtime.

Question 9

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:1.0
        ports:
        - containerPort: 8080
```

Question 10

What is a ReplicaSet in Kubernetes?

Accepted Answer

A ReplicaSet ensures that a specified number of Pod replicas are running at any given time. It's primarily used by Deployments to manage Pod scaling and self-healing. You typically don't interact with ReplicaSets directly when using Deployments.

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 Pods, even if the underlying Pods are created, deleted, or moved.

Question 12

Name and describe three common Service Types in Kubernetes.

Accepted Answer

1. `ClusterIP`: Exposes the Service on an internal IP in the cluster. Only reachable from within the cluster. Default type. 2. `NodePort`: Exposes the Service on each Node's IP at a static port (the `NodePort`). Makes the Service accessible from outside the cluster using `:`. 3. `LoadBalancer`: Exposes the Service externally using a cloud provider's load balancer. Only works with cloud providers that support it.

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 # Service port
    targetPort: 8080 # Container port
  type: ClusterIP
```

Question 14

What is a Namespace in Kubernetes?

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 a scope for names and preventing naming collisions.

Question 15

What is a ConfigMap in Kubernetes?

Accepted Answer

A ConfigMap is an API object used to store non-sensitive configuration data in key-value pairs. It allows you to decouple configuration artifacts from image content, making applications more portable and easier to manage.

Question 16

What is a Secret in Kubernetes?

Accepted Answer

A Secret is an API object used to store sensitive information, such as passwords, OAuth tokens, and SSH keys. It provides a more secure way to store and manage sensitive data than ConfigMaps, though the data is only base64 encoded by default, not encrypted at rest without additional configuration.

Question 17

What is a Volume in Kubernetes?

Accepted Answer

A Volume in Kubernetes is a directory accessible to the containers in a Pod. It provides data persistence beyond the life of a container and allows data to be shared between containers within the same Pod.

Question 18

Name and describe two common Kubernetes Volume types.

Accepted Answer

1.  `emptyDir`: A simple empty directory created when a Pod is assigned to a node. It's temporary and deleted when the Pod is removed from the node. Useful for temporary data or sharing data between co-located containers.
2.  `hostPath`: Mounts a file or directory from the host node's filesystem into a Pod. Useful for accessing host-specific data, but not recommended for most production uses due to lack of portability and security concerns.
3.  `PersistentVolumeClaim (PVC)`: A request for storage by a user. It abstracts the underlying storage details, allowing users to consume storage without knowing the specifics of the storage infrastructure.

Question 19

What is Ingress in Kubernetes?

Accepted Answer

Ingress is an API object that manages external access to services in a cluster, typically HTTP/S. It provides HTTP and HTTPS routing to services based on hostnames or URL paths, acting as a layer 7 load balancer. An Ingress controller is required to fulfill the Ingress rules.

Question 20

Provide a basic YAML structure for a Kubernetes Ingress.

Accepted Answer

```yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: my-app-ingress
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: my-app-service
            port:
              number: 80
```

Question 21

What is a StatefulSet in Kubernetes?

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 or other applications requiring stable identities.

Question 22

What is a DaemonSet in Kubernetes?

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 23

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 YAML 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.

Question 24

Briefly describe the roles of Kubelet and Kube-proxy on a Kubernetes Worker Node.

Accepted Answer

*   **Kubelet**: An agent that runs on each worker node. It ensures that containers are running in a Pod and healthy, communicating with the Control Plane (API Server).
*   **Kube-proxy**: A network proxy that runs on each node. It maintains network rules on nodes, allowing network communication to your Pods from inside or outside of the cluster.

Kubernetes - Container Orchestration, Pods & Deployments

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