Kubernetes & Container Orchestration - Pod Architecture, Services & Ingress Flashcards

Question 1

What is 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. `Services` enable loose coupling between dependent `Pods` and provide a stable IP address and DNS name for a set of `Pods`.

Question 2

What is Kubernetes?

Accepted Answer

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications.

Question 3

What is a Kubernetes Pod?

Accepted Answer

A `Pod` is the smallest deployable unit in Kubernetes, representing a single instance of a running process in a cluster. A `Pod` encapsulates one or more containers, storage resources, a unique network IP, and options that govern how the containers should run.

Question 4

Describe the key phases of a Pod's lifecycle.

Accepted Answer

A `Pod` progresses through several phases:
*   `Pending`: The `Pod` has been accepted by the Kubernetes cluster, but one or more of the container images has not been created.
*   `Running`: The `Pod` has been bound to a node, and all of the containers have been created. At least one container is still running, or is in the process of starting or restarting.
*   `Succeeded`: All containers in the `Pod` have terminated successfully, and will not be restarted.
*   `Failed`: All containers in the `Pod` have terminated, and at least one container has terminated in failure (exited with a non-zero status code).
*   `Unknown`: For some reason, the state of the `Pod` could not be obtained.

Question 5

What is a Kubernetes Node?

Accepted Answer

A `Node` is a worker machine in Kubernetes, which can be a VM or a physical machine. Each `Node` contains the necessary services to run `Pods`, including the `kubelet` (agent for the master), `kube-proxy` (network proxy), and a container runtime (e.g., Docker, containerd).

Question 6

What is the Kubernetes Control Plane (Master)?

Accepted Answer

The `Control Plane` manages the worker `Nodes` and the `Pods` in the cluster. It consists of several components: `kube-apiserver`, `etcd`, `kube-scheduler`, and `kube-controller-manager`.

Question 7

List the core components of the Kubernetes Control Plane and their primary functions.

Accepted Answer

*   `kube-apiserver`: Exposes the Kubernetes API; frontend for the control plane.
*   `etcd`: Consistent and highly-available key-value store for all cluster data.
*   `kube-scheduler`: Watches for new `Pods` and assigns them to `Nodes`.
*   `kube-controller-manager`: Runs controller processes (e.g., `Node` controller, `ReplicaSet` controller) to move the cluster's current state towards the desired state.

Question 8

What is `kubelet`?

Accepted Answer

`kubelet` is an agent that runs on each `Node` in the cluster. It ensures that containers are running in a `Pod` and healthy. It communicates with the `Control Plane`, receives `Pod` specifications, and manages the `Pods` and their containers on its `Node`.

Question 9

What is `kube-proxy`?

Accepted Answer

`kube-proxy` is 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. It handles service discovery and load balancing for `Services`.

Question 10

What is a Kubernetes Deployment?

Accepted Answer

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

Question 11

How do Deployments manage Pod updates and rollouts, specifically the `RollingUpdate` strategy?

Accepted Answer

`Deployments` use `ReplicaSets` to manage `Pods`. When a `Deployment` is updated (e.g., new image version), it creates a new `ReplicaSet` with the updated configuration, gradually scales up the new `ReplicaSet` while scaling down the old one. This `RollingUpdate` strategy ensures zero downtime by incrementally replacing old `Pods` with new ones.

Question 12

Differentiate between `ClusterIP`, `NodePort`, and `LoadBalancer` Service types.

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 each `Node`'s IP at a static port (the `NodePort`). Makes the `Service` accessible from outside the cluster using `:`. * `LoadBalancer`: Exposes the `Service` externally using a cloud provider's load balancer. This type automatically provisions an external load balancer, which routes traffic to the `NodePort` `Service`.

Question 13

What is Kubernetes Ingress?

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 14

What is an Ingress Controller?

Accepted Answer

An `Ingress Controller` is a specialized `Pod` that runs in the cluster and watches the Kubernetes API for `Ingress` resources. It's responsible for fulfilling the `Ingress`, usually by configuring a load balancer (like Nginx, HAProxy, or a cloud provider's LB) to route traffic according to the `Ingress` rules.

Question 15

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.

Question 16

What is a Secret?

Accepted Answer

A `Secret` is an API object used to store sensitive information, such as passwords, OAuth tokens, and SSH keys. It's similar to `ConfigMap` but is designed for confidential data and provides basic encoding (Base64) and access control mechanisms.

Question 17

When would you use a `ConfigMap` versus a `Secret`?

Accepted Answer

Use a `ConfigMap` for non-sensitive configuration data (e.g., application settings, environment variables, command-line arguments). Use a `Secret` for sensitive data that requires protection (e.g., database credentials, API keys, private certificates). `Secrets` offer better security practices for sensitive data.

Question 18

What is a PersistentVolume (PV)?

Accepted Answer

A `PersistentVolume` (PV) is an abstract storage resource in the cluster, provisioned by an administrator or dynamically provisioned using `StorageClasses`. It's a piece of storage in the cluster that has been provisioned by an administrator. It is a resource in the cluster just like a `Node` is a cluster resource.

Question 19

What is a PersistentVolumeClaim (PVC)?

Accepted Answer

A `PersistentVolumeClaim` (PVC) is a request for storage by a user. It consumes `PV` resources. `PVCs` are requests for specific sizes and access modes (e.g., `ReadWriteOnce`, `ReadOnlyMany`) of storage.

Question 20

Explain the relationship between PVs and PVCs.

Accepted Answer

A `PersistentVolume` (PV) is the actual storage resource available in the cluster, while a `PersistentVolumeClaim` (PVC) is a request for that storage by a `Pod`. A `PVC` binds to a `PV` that meets its requirements, making the storage available to the `Pod`.

Question 21

What is a `ReplicaSet` and how does it relate to Deployments?

Accepted Answer

A `ReplicaSet` ensures that a specified number of `Pod` replicas are running at any given time. `Deployments` own and manage `ReplicaSets` to provide declarative updates to `Pods`, handling the creation, deletion, and scaling of `Pods` through the `ReplicaSet`.

Question 22

What is a `StatefulSet` and when is it used?

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 identifiers, and stable persistent storage. It's used for applications like databases (e.g., MySQL, PostgreSQL) or message queues (e.g., Kafka) that require stable identities and ordered deployments.

Question 23

What is a `DaemonSet` and when is it used?

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 from the cluster, those `Pods` are garbage collected. It's typically used for cluster-level operations like log collection (`fluentd`), monitoring agents (`Prometheus Node Exporter`), or storage daemons.

Question 24

Provide examples of common `kubectl` commands for managing Pods and resources.

Accepted Answer

Here are some common `kubectl` commands: * List `Pods`: `kubectl get pods` * Get detailed info about a `Pod`: `kubectl describe pod ` * View `Pod` logs: `kubectl logs ` * Execute a command in a `Pod`: `kubectl exec -it -- /bin/bash` * Apply a manifest file: `kubectl apply -f `

Question 25

How do you scale a Deployment using `kubectl`?

Accepted Answer

To scale a `Deployment` to a desired number of replicas, you can use the `kubectl scale` command: ```bash kubectl scale deployment --replicas= ``` For example, to scale a deployment named `my-app-deployment` to 5 replicas: `kubectl scale deployment my-app-deployment --replicas=5`.

Kubernetes & Container Orchestration - Pod Architecture, Services & Ingress

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