Kubernetes Administration - Architecture, Pod Lifecycle & Ingress Networking Flashcards

Question 1

How do you get detailed information about a Pod named `my-pod`?

Accepted Answer

`kubectl describe pod my-pod`

Question 2

How do you imperatively create a Pod named `nginx-pod` running the `nginx` image?

Accepted Answer

`kubectl run nginx-pod --image=nginx`

Question 3

How do you imperatively expose a Deployment named `my-app` as a `NodePort` Service on port 80?

Accepted Answer

`kubectl expose deployment my-app --type=NodePort --port=80`

Question 4

How do you view the logs of a Pod named `my-pod`?

Accepted Answer

`kubectl logs my-pod`

Question 5

How do you delete a Pod named `my-pod`?

Accepted Answer

`kubectl delete pod my-pod`

Question 6

What is the primary function of the `kube-apiserver` in Kubernetes?

Accepted Answer

The `kube-apiserver` is the frontend for the Kubernetes control plane, exposing the Kubernetes API. It processes REST requests, validates them, and updates the state of API objects in `etcd`.

Question 7

What is `etcd` and its role in a Kubernetes cluster?

Accepted Answer

`etcd` is a consistent and highly available key-value store used as Kubernetes' backing store for all cluster data. It stores the cluster's configuration, state, and metadata.

Question 8

Explain the role of the `kube-scheduler`.

Accepted Answer

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

Question 9

What is the `kube-controller-manager` responsible for?

Accepted Answer

The `kube-controller-manager` runs controller processes that regulate the state of the cluster. Each controller (e.g., Node Controller, Replication Controller, Endpoints Controller, Service Account Controller) watches a specific resource type and works to move the current state towards the desired state.

Question 10

What is the `kubelet` and where does it run?

Accepted Answer

The `kubelet` is an agent that runs on each node in the cluster. It ensures that containers are running in a Pod. It takes a set of PodSpecs provided through various mechanisms and ensures that the described containers are healthy and running.

Question 11

What is the `kube-proxy` and its function?

Accepted Answer

The `kube-proxy` runs on each node and maintains network rules on the nodes. These rules allow network communication to your Pods from inside or outside of your cluster. It handles Service abstraction by forwarding traffic to the correct backend Pods.

Question 12

List the main phases of a Kubernetes Pod's lifecycle.

Accepted Answer

The main phases are `Pending`, `Running`, `Succeeded`, `Failed`, and `Unknown`.

Question 13

Describe the `Pending` phase of a Pod.

Accepted Answer

A Pod is in the `Pending` phase when it has been accepted by the Kubernetes system, but one or more of its container images have not been created. This includes time spent by the Pod in scheduling and downloading images.

Question 14

When is a Pod considered to be in the `Running` phase?

Accepted Answer

A Pod is in the `Running` phase when all containers in the Pod have been created and at least one container is running, or is in the process of starting or restarting.

Question 15

What does the `Succeeded` phase indicate for a Pod?

Accepted Answer

A Pod is in the `Succeeded` phase when all containers in the Pod have terminated successfully, and will not restart. This typically applies to batch jobs.

Question 16

What does the `Failed` phase indicate for a Pod?

Accepted Answer

A Pod is in the `Failed` phase when one or more containers in the Pod terminated in failure (exited with a non-zero status code), and the system will not restart them.

Question 17

What are `liveness probes` in Kubernetes?

Accepted Answer

`Liveness probes` are used by the `kubelet` to know when to restart a container. If a liveness probe fails, the `kubelet` kills the container, and the container is subject to its restart policy.

Question 18

What are `readiness probes` in Kubernetes?

Accepted Answer

`Readiness probes` are used by the `kubelet` to know when a container is ready to start serving traffic. If a readiness probe fails, the Endpoints Controller removes the Pod's IP address from the Endpoints of all Services that match the Pod.

Question 19

Explain the `ClusterIP` Service type.

Accepted Answer

A `ClusterIP` Service exposes the Service on an internal IP in the cluster. It's the default type and makes the Service only reachable from within the cluster.

Question 20

Explain the `NodePort` Service type.

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 makes the Service accessible from outside the cluster using `:`.

Question 21

Explain the `LoadBalancer` Service type.

Accepted Answer

A `LoadBalancer` Service exposes the Service externally using a cloud provider's load balancer. Cloud providers provision a load balancer that automatically routes external traffic to the `NodePort` and `ClusterIP` Services.

Question 22

What is the purpose of a Kubernetes `Service`?

Accepted Answer

A Kubernetes `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, enabling reliable access even as Pods are created, deleted, or moved.

Question 23

What is Kubernetes `Ingress` used for?

Accepted Answer

`Ingress` exposes HTTP and HTTPS routes from outside the cluster to services within the cluster. It provides external access to services with features like load balancing, SSL termination, and name-based virtual hosting.

Question 24

What is an `Ingress Controller`?

Accepted Answer

An `Ingress Controller` is a specialized deployment that watches the Kubernetes API server for `Ingress` resources. It then configures a load balancer or reverse proxy (e.g., Nginx, HAProxy, Traefik) to route traffic according to the `Ingress` rules.

Question 25

Provide an example of a basic `Ingress` rule definition.

Accepted Answer

```yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: example-ingress
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80
```
This rule routes traffic for `myapp.example.com/` to `myapp-service` on port 80.

Kubernetes Administration - Architecture, Pod Lifecycle & Ingress Networking

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