Introduction to Kubernetes

Question 1

Kubernetes helps you manage applications that are made up of

Answer 1

hundreds or maybe thousands of containers.

Question 2

Kubernetes helps you manage applications that are in different environments like

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physical machines, virtual machines, cloud environments or even hybrid deployment environments.

Question 3

How the need for an orchestration tool evolved:

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★ Trend from Monolith to microservices
★ Increased usage of containers
★ Managing those hundreds or thousands of containers

Question 4

Features of container orchestration tools

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• High availability
• Scalability
• Disaster Recovery

Question 5

The cluster must have at least one :

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​Master Node.​

Question 6

Connected to the Master Node you have a couple of

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Worker Nodes, where each Node has a Kubelet process running on it.

Question 7

A Kubelet is a Kubernetes process that makes it possible for

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all cluster nodes to communicate with each other and execute tasks on Worker Nodes, like starting a web application container or database containers.

Question 8

The ​Master Node runs several Kubernetes processes that are absolutely necessary to manage the cluster properly. These processes are:

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● API server
● Controller Manager
● Scheduler

Question 9

API server, which also is a container. An API server is the

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entry point to the Kubernetes cluster It is the process, which the different Kubernetes clients will talk to.

Question 10

Kubernetes clients are:

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● UI - when using Kubernetes dashboard
● API - when using scripts and automating technologies or
● CLI - Kubernetes command-line tool (kubectl)

Question 11

Controller Manager keeps an overview of

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what is happening in the cluster. Whether something needs to be repaired or maybe if a container died and it needs to be restarted.

Question 12

Scheduler is responsible for scheduling containers on

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different Nodes based on the workload and the available server resources on each Node.

Question 13

etcd is a key value storage which holds at any time

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the current state of the Kubernetes cluster

Question 14

etcd stores all the ________ data and all the ____ data of each Node and each container inside of that Node.

Answer 14

configuration data ; status data

Question 15

Using that etcd snapshot you can

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recover the whole cluster state.

Question 16

etcd snapshots allows Kubernetes to heal itself using

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the backup and restore made of the current state of all components in your cluster.

Question 17

the control plane is responsible for making decisions about the cluster and

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pushing it toward the desired state.

Question 18

Virtual Network enables the communication between

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Worker Nodes and Master Nodes.

Question 19

The Virtual network ​spans

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all the Nodes that are part of the cluster​.

Question 20

a virtual network turns all the Nodes inside of the cluster into one

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powerful machine that has the sum of all the resources of individual Nodes.

Question 21

If for example you lose a Master Node access you will not be able to access

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the cluster anymore
Have a backup of your master at all time is non-negotiable

Question 22

Think of a Pod as a ________ over a container.

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wrapper

Question 23

On each Worker Node you can have multiple

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Pods and inside of a Pod you can again have multiple containers. Even though its best practice to only have one application per Pod. Unless a dependency is required.

Question 24

Pod is a component of Kubernetes that manages the containers running inside itself without our intervention. If a container

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stops or dies inside of a Pod it will automatically be restarted inside the Pod.

Question 25

Pods get assigned dynamic IP address by ddefualt but you wanted a persistent address

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You would have to associate Services to that Pod to provide a persistent static IP address.

Question 26

each application Pod gets its own Service sitting in front of it, to handle

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the communication with other pods.

Question 27

If a Pod behind the Service dies and gets recreated the Service stays in place, because

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its lifecycle is not tied to the lifecycle of the pod.

Question 28

The Service has two main functionalities.

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Providing a **static IP address.** **Load balancer** functionality.

Question 29

if you have 3 Pods of the same application, you can use the

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same service to handle communication with all 3 pods

Question 30

How do we actually create those components, like Pods and Services in Kubernetes cluster?

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Kubernetes clients, like Kubernetes dashboard, Kubernetes API or a command line tool kubectl, all talk to the API server. Using these clients you can send configuration requests to the

Question 31

Deployment is essentially a Yaml file that acts as a

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blueprint for creating Pods and that blueprint is defined in the template attribute under the specifications section

Question 32

Configuration requests in Kubernetes are written in ____ ____

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declarative form

Question 33

A declarative syntax form means we

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declare what our desired outcome is and Kubernetes tries to meet those requirements.