Basics

Question 1

Kubernetes is composed of two separate planes:

Answer 1

Control Plane and Data plane

Question 2

What does this statement refer to?: machines that can run containerized workloads. Each node is managed by the kubelet, an agent that receives commands from the control plane.

Answer 2

Kubernetes data plane

Question 3

What does this statement refer to?: manages Kubernetes clusters and the workloads running on them. Include components like the API Server, Scheduler, and Controller Manager.

Answer 3

Kubernetes control plane

Question 4

What is the smallest unit of Kubernetes?

Answer 4

The pod. A pod typically includes several containers, which together form a functional unit or microservice.

Question 5

Why is persistent storage important?

Answer 5

local storage on Kubernetes nodes is ephemeral, and is deleted when a pod shuts down. This can make it difficult to run stateful applications. Kubernetes provides the Persistent Volumes (PV) mechanism, allowing containerized applications to store data beyond the lifetime of a pod or node.

Question 6

________ is a database that stores information in a key value format.

Answer 6

ETCD Cluster

Question 7

______________is a control plane process which assigns Pods to Nodes. ______________determines which Nodes are valid placements for each Pod in the scheduling queue according to constraints and available resources. _____________then ranks each valid Node and binds the Pod to a suitable Node.

Answer 7

The scheduler

Question 8

the ____________ is responsible for orchestrating all operations within the cluster.

Answer 8

kube-apiserver

Question 9

the ______________ is an agent that runs on each node in a cluster, it deploys or destroys containers in the node as required. It listens from instructions from the kube-apiserver.

Answer 9

kubelet

Question 10

what does the kube-proxy do?

Answer 10

Its responsible for the communication between services within the cluster.

Question 11

The master node is comprised by:

Answer 11

ETCD Cluster, kube-apiserver, kube Controller Manager and Kube-scheduler.

Question 12

The worker nodes are comprised by:

Answer 12

the kubelet, kube-proxy and the container runtime engine.

Question 13

Reminisce on Docker and Containerd history and how Kubernetes only kept docker’s daemon rather than also sticking with the other componentes like the volumes, image building features, etc:

Answer 13

Kubernetes used to rely on Docker to manage containers, but it only needed Docker’s container runtime, not the extra features like image building. To make things simpler, Kubernetes switched to using containerd, which is the part of Docker that actually runs containers. They removed support for Docker through something called dockershim. This change made Kubernetes faster and more efficient because it could talk directly to containerd without needing Docker in the middle.

Question 14

why use nerdctl cli over ctr cli?

Answer 14

ctr is for debugging purposes only and its not the most user friendly tool. Contrary to nerdctl as it provides a Docker-like CLI for containerD.

Question 15

what is a key value store?

Answer 15

a key value store stores information in the form of forms or documents. Changing one file doesnt affect the others.

Question 16

True or false: every change made to the cluster is updated in the etcd server, only then, is the change considered to be complete.

Answer 16

True

Question 17

Default port on which etcd listens

Answer 17

2379

Question 18

What are the implications of deploying a cluster from scratch:

Answer 18

• You install and configure each component manually (etcd, API server, scheduler, controller manager, kubelet, kube-proxy).
• Gives complete control over the configuration.
• Requires deep knowledge of Kubernetes internals.

Question 19

What are the implications of using Kubeadm for the deployment of the Cluster:

Answer 19

• Automated setup
• Follows best practices by default.
• Some configurations are abstracted away for simplicity.

Question 20

There are two things that need to be specified when using etcdctl api (the first thing is necessary for commands to be usable and the second one is for authentication purposes):

Answer 20

1) Its necessary to specify api version (its possible to choose between version 2 and 3):
export ETCDCTL_API=3

2) Its necessary to specify the path where the ssl certificate is.

Question 21

The only component that interacts directly with etcdserver is:

Answer 21

the kube-api server

Question 22

What does the kube controller manager do?

Answer 22

It watches the API server for changes (like creating or deleting Pods) and makes sure the cluster matches the desired state.
For example, if a Pod crashes, it notices and starts a new one to replace it.

Question 23

What things does the kubecontroller manager admins:

Answer 23

the node controller - health checks
replication controller - ensures the right number of read replicas are runnning.
endpoint controller - updates endpoints objects when services or pods change.
service account & token controllers - manages service accounts and their access tokens.

Question 24

What is the node monitor period?

Answer 24

5 seconds

Question 25

what are kubernetes services?

Answer 25

Virtual components thaet reside within kubernetes engine

Question 26

Talk about Networking in Kubernetes

Answer 26

Pod communication - Pods can communicate across nodes without NAT using a flat network space. Service Discovery - Services provide stable IPs and DNS names for pods, enabling easy discovery. Network Policies - Control traffic flow between pods.

Question 27

kube-proxy's Role when it comes to service routing, operating modes and load balancing:

Answer 27

Service Routing: Manages network rules to direct traffic to the right pods by watching changes in Services and Endpoints. The operating modes are: ip-tables which are fast and scalable, ipvs (this is robust load balancing using Linux virtual Server) and lastly Userspace, which is a legacy mode, less common. Load Balancing: distributes requests evenly across pod replicas.

Question 28

What is a pod?

Answer 28

the containers are encapsulated in pods, a pod is a single instance of an application and the smallest object that you can create in Kubernetes.

Question 29

Are we limited to having a single container within a pod?

Answer 29

NO. However, when it comes to scaling the application, its best to have multiple nodes.

Question 30

Kubernetes uses _______ files to define resources like Pods, Services and Deployments in a structured human-readable format.

Answer 30

YAML

Question 31

Regarding the key components of the Kubernetes YAML file: what does the apiVersion do?

Answer 31

specifies the Kubernetes API version.

Question 32

Regarding the key components of the Kubernetes YAML file: the ______ defines the resource type (eg. Pod, Service, Deployment)

Answer 32

kind

Question 33

Regarding the key components of the Kubernetes YAML file: _______ contains the resource's name, labels, and namespace.

Answer 33

metadata

Question 34

Regarding the key components of the Kubernetes YAML file: ________ describes the desired estate, such as container images, replicas, or networking rules.

Answer 34

spec

Question 35

about the Kubernetes cheat sheet:

Answer 35

create pods with given image: kubectl run nginx --image=nginx create pods from yaml file: kubectl create -f pods.yaml get pods: kubectl get pods get specific pod: kubectl get pods/webapp describe a pod: kubectl describe pods discover where nodes are placed: kubectl get pods -o wide Using the dry run option: eg. kubectl run redis --image=redis123 --dry-run -o yaml kubectl run redis --image=redis123 --dry-run=client -o yaml > redis.yaml kubectl Apply changes made into a yaml file: kubectl apply -f redis.yaml

Question 36

What is the replication controller in Kubernetes?

Answer 36

A Kubernetes object that manages the number of copies of a pod that are running.

Question 37

What's the difference between the replication controller and the replica set in Kubernetes?

Answer 37

Both have the same function, the replication controller is the old technology used to manage the pod replicas, and it is being replaced by replica set.

Question 38

True or false: The selector is required when it comes to the replica set file

Answer 38

true

Question 39

Some replica set commands:

Answer 39

kubectl create -f rpl.yml kubectl get rplset kubectl delete replicaset myapp-replicaset kubectl replace -f replicaset-definition.yml kubectl scale -replicas=6 -f replicaset-definition.yml {scaling the replica set without having to make changes to yml file.

Question 40

Talk about Kubernetes deployments:

Answer 40

Deployments are one level up from ReplicaSets. They allow you to use a declarative method to deploy ReplicaSets and pods.

Question 41

True or false: Just like a ReplicaSet, in a deployment, you cannot modify the YAML Pod template, and the deployment wont take care of rolling out the changes.

Answer 41

False: Unlike a ReplicaSet, in a deployment, you can modify the YAML Pod template, and the deployment will take care of rolling out the changes. You can roll back to a previous version of your configuration if necessary.

Question 42

If I want to create a deployment named Emily with 3 replica sets and nginx image, but dont want to incur in the creation of a yaml file, what command can I use?

Answer 42

kubectl create deployment --replicas=3 --image=nginx Emily

Question 43

What do Kubernetes services do?

Answer 43

Help us establish connection across applications and enable communication to outside users.

Question 44

Service types in Kubernetes:

Answer 44

NodePort ClusterIP LoadBalancer

Question 45

Whats the range supported by NodePorts?

Answer 45

30000 to 32767

Question 46

True or false: the ips on a kubernetes pod are static.

Answer 46

False

Question 47

_______________are responsible for facilitating communication between cluster components. At their core, ______________provide a way for Pods to discover and connect to backend services. This is achieved by dynamically updating a list of network addresses associated with a particular service.

Answer 47

endpoints

Question 48

What is a Kubernetes Cluster?

Answer 48

Namespaces are a way to organize clusters into virtual sub-clusters — they can be helpful when different teams or projects share a Kubernetes cluster.

Question 49

Kubernetes comes with three namespaces out-of-the-box. They are:

Answer 49

default, kube-system and kube-public

Question 50

get all namespcaces command

Answer 50

kubectl get ns -A

Question 51

whats the difference between imperative and declarative?

Answer 51

The imperative way gives a set of instructions for a result to be achieved, for example, all the instructions you need to set up an nginx web server. In the declarative way, you would utilize docker compose (a yaml) to declare the version of nginx you want to deploy in a container and if by any chance you want to change the nginx version, you can do so within the yaml and then run docker-compose up.

Question 52

what kubectl command is used to check for changes and applying them in a yaml file?

Answer 52

kubectl apply -f nginx.yaml

Question 53

Is there such thing as ResourceQuota in Kubernetes?

Answer 53

Yes, you can create declarative yaml files specifying resource quotas within a namespace.

Question 54

what command flag does this? By default as soon as the command is run, the resource will be created.

Answer 54

--dry-run

Question 55

If you simply want to test your command , use the________option.

Answer 55

--dry-run=client

Question 56

what does this command flag do (-o yaml) ?

Answer 56

This will output the resource definition in YAML format on screen.