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Add a couple of Virtualization questions
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119 changes: 101 additions & 18 deletions README.md
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:information_source:  This repo contains questions and exercises on various technical topics, sometimes related to DevOps and SRE :)

:bar_chart:  There are currently **1540** questions
:bar_chart:  There are currently **1553** questions

:books:  To learn more about DevOps and SRE, check the resources in [devops-resources](https://github.com/bregman-arie/devops-resources) repository

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<td align="center"><a href="#testing"><img src="images/testing.png" width="75px;" height="75px;" alt="Testing"/><br /><b>Testing</b></a></td>
<td align="center"><a href="#databases"><img src="images/databases.png" width="75px;" height="75px;" alt="Databases"/><br /><b>Databases</b></a></td>
<td align="center"><a href="#regex"><img src="images/regex.png" width="75ph;" height="75px;" alt="RegEx"/><br /><b>Regex</b></a></td>
<td align="center"><a href="https://github.com/bregman-arie/system-design-exercises"><img src="images/design.png" width="110px;" height="75px;" alt="Design"/><br /><b>System Design</b></a></td>
<td align="center"><a href="#system-design"><img src="images/design.png" width="110px;" height="75px;" alt="Design"/><br /><b>System Design</b></a></td>
<td align="center"><a href="#hardware"><img src="images/hardware.png" width="110px;" height="75px;" alt="Hardware"/><br /><b>Hardware</b></a></td>
<td align="center"><a href="#big-data"><img src="images/big-data.png" width="110px;" height="75px;" alt="Big Data"/><br /><b>Big Data</b></a></td>
<td align="center"><a href="#questions-you-ask"><img src="images/you.png" width="110px;" height="75px;" alt="you"/><br /><b>Questions you ask</b></a></td>
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<!-- prettier-ignore-end -->
<!-- ALL-TOPICS-LIST:END -->

## Linux Master Application

A completely free application for testing your knowledge on Linux

<a href="https://play.google.com/store/apps/details?id=com.codingshell.linuxmaster"><img src="images/linux_master.jpeg"/></a>

## DevOps

<details>
Expand Down Expand Up @@ -474,6 +468,14 @@ Note: cross-dependency is when you have two or more changes to separate projects
<summary>What is Distributed Tracing?</summary><br><b>
</b></details>

<details>
<summary>What is GitOps?</summary><br><b>

GitLab: "GitOps is an operational framework that takes DevOps best practices used for application development such as version control, collaboration, compliance, and CI/CD tooling, and applies them to infrastructure automation".

Read more [here](https://about.gitlab.com/topics/gitops)
</b></details>

#### SRE

<details>
Expand Down Expand Up @@ -721,6 +723,10 @@ It's important to note that:
* Serverless Computing allows you to have a different paying model. You basically pay only when your functions are running and not when the VM or containers are running as in other payment models
</b></details>

<details>
<summary>Can we replace any type of computing on servers with serverless?</summary><br><b>
</b></details>

<details>
<summary>Is there a difference between managed service to SaaS or is it the same thing?</summary><br><b>
</b></details>
Expand Down Expand Up @@ -3945,6 +3951,12 @@ MemAvailable - The amount of available memory for new workloads (without pushing
<summary>Why there are different sections in man? What is the difference between the sections?</summary><br><b>
</b></details>

#### Linux Master Application

A completely free application for testing your knowledge on Linux

<a href="https://play.google.com/store/apps/details?id=com.codingshell.linuxmaster"><img src="images/linux_master.jpeg"/></a>

## Operating System

<details>
Expand Down Expand Up @@ -4046,6 +4058,42 @@ Cache: Cache is usually used when processes reading and writing to the disk to m
<summary>Explain what is Virtualization</summary><br><b>
</b></details>

<details>
<summary>What is a hypervisor?</summary><br><b>

Red Hat: "A hypervisor is software that creates and runs virtual machines (VMs). A hypervisor, sometimes called a virtual machine monitor (VMM), isolates the hypervisor operating system and resources from the virtual machines and enables the creation and management of those VMs."

Read more [here](https://www.redhat.com/en/topics/virtualization/what-is-a-hypervisor)
</b></details>

<details>
<summary>What types of hypervisors are there?</summary><br><b>

Hosted hypervisors and bare-metal hypervisors.
</b></details>

<details>
<summary>What are the advantages and disadvantges of bare-metal hypervisor over a hosted hypervisor?</summary><br><b>

Due to having its own drivers and a direct access to hardware components, a baremetal hypervisor will often have better performances along with stability and scalability.

On the other hand, there will probably be some limitation regarding loading (any) drivers so a hosted hypervisor will usually benefit from having a better hardware compatibility.
</b></details>

<details>
<summary>What types of virtualization are there?</summary><br><b>

Operating system virtualization
Network functions virtualization
Desktop virtualization
</b></details>

<details>
<summary>Is containerization is a type of Virtualization?</summary><br><b>

Yes, it's a operating-system-level virtualization, where the kernel is shared and allows to use multiple isolated user-spaces instances.
</b></details>

<details>
<summary>What is "time sharing"?</summary><br><b>

Expand Down Expand Up @@ -4663,8 +4711,9 @@ Output variables are named values that are sourced from the attributes of a modu
The primary difference between containers and VMs is that containers allow you to virtualize
multiple workloads on the operating system while in the case of VMs the hardware is being virtualized to
run multiple machines each with its own OS.
You can also think about it as containers are for OS-level virtualization while VMs are for hardware virtualization.

* Containers don't require an entire guest operating system as VMs
* Containers don't require an entire guest operating system as VMs. Containers share the system's kernel as opposed to VMs
* It usually takes a few seconds to set up a container as opposed to VMs which can take minutes or at least more time than containers as there is an entire OS to boot and initialize as opposed to container where you mainly lunch the app itself
* Containers are isolated from each other, but not as concretely as virtual machines. It is possible for a malicious user to break into the host OS from a container and vice versa.
</b></details>
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<summary>Explain what is a pod</summary><br><b>
</b></details>

<details>
<summary>Deploy a pod called "my-pod" using the nginx:alpine image</summary><br><b>

`kubectl run my-pod --image=nginx:alpine --restart=Never`
</b></details>

<details>
<summary>How many containers can a pod contain?</summary><br><b>

Expand Down Expand Up @@ -5050,13 +5105,25 @@ Another way is using the deployment configuration file: `kubectl delete -f deplo
The pod related to the deployment will terminate and the replicaset will be removed.
</b></details>

<details>
<summary>How make an app accessible on private or external network?</summary><br><b>

Using a Service.
</b></details>

#### Kubernetes Service

<details>
<summary>What is a Service in Kubernetes?</summary><br><b>
"An abstract way to expose an application running on a set of Pods as a network service." - more [here](https://kubernetes.io/docs/concepts/services-networking/service)
"An abstract way to expose an application running on a set of Pods as a network service." - read more [here](https://kubernetes.io/docs/concepts/services-networking/service)

In simpler words, it allows you to expose the service by attaching permanent IP address for example to a certain pod.
</b></details>

<details>
<summary>True or False? The lifecycle of Pods and Services isn't connected so when a pod dies, the service still stays </summary><br><b>

Note: Even if connected to a pod, their lifecycles aren't connected.
True
</b></details>

<details>
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## Security

<details>
<summary>Can you describe the DevSecOps core principals? (or what is DevSecOps)</summary><br><b>
<summary>What is DevSecOps? What its core principals?</summary><br><b>
</b></details>

<details>
Expand Down Expand Up @@ -9780,7 +9847,13 @@ Access control based on user roles (i.e., a collection of access authorizations

</b></details>

## Security SSH
## Security - Web

<details>
<summary>What is Nonce?</summary><br><b>
</b></details>

## Security - SSH

<details>
<summary>What is SSH how does it work?</summary><br><b>
Expand Down Expand Up @@ -11309,11 +11382,7 @@ Bonus: extract the last word of each line
<summary>Replace 'red' with 'green'</summary><br><b>
</b></details>

## System Designotebookn

This section contains only questions on System Design subject. The exercises can be found in [system-design-notebook repository](https://github.com/bregman-arie/system-design-notebook).

#### Architecture
#### System Design

<details>
<summary>Explain what is a "Single point of failure" and give an example</summary><br><b>
Expand Down Expand Up @@ -11400,6 +11469,10 @@ A load balancer. You can add more resources, but if you would like them to be pa
Also, data inconsistency is a concern with horizontal scaling.
</b></details>

<details>
<summary>Explain when in which use cases will you use vertical scaling and in which use cases you will use horizontal scaling</summary><br><b>
</b></details>

<details>
<summary>Explain Resiliency and what ways are there to make a system more resilient</summary><br><b>
</b></details>
Expand Down Expand Up @@ -11502,6 +11575,12 @@ DNS redirection
<summary>How would you build a URL shortener?</summary><br><b>
</b></details>

#### More System Design Questions

Additional exercises can be found in [system-design-notebook repository](https://github.com/bregman-arie/system-design-notebook).

<p align="center"><a href="https://github.com/bregman-arie/system-design-notebook"><img src="images/system_design_notebook.png"/></a></p>

## Hardware

<details>
Expand Down Expand Up @@ -11580,6 +11659,10 @@ An answer from [talend.com](https://www.talend.com/resources/what-is-data-archit
<summary>What is "Data Versioning"? What models of "Data Versioning" are there?</summary><br><b>
</b></details>

<details>
<summary>What is ETL?</summary><br><b>
</b></details>

#### Apache Hadoop

<details>
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## Certified Kubernetes Administrator (CKA)

#### Basic Commands

<details>
<summary>Which command you run to view your nodes?</code></summary><br><b>

`kubectl get nodes`
</b></details>

<details>
<summary>Which command you run to view all pods running on all namespaces?</code></summary><br><b>

`kubectl get pods --all-namespaces`
</b></details>

<details>
<summary>How to list all namespaces?</code></summary><br><b>

`kubectl get namespaces`
</b></details>

<details>
<summary>How to create a deployment?</code></summary><br><b>

```
cat << EOF | kubectl create -f -
> apiVersion: v1
> kind: Pod
> metadata:
> name: nginx
> spec:
> containers:
> - name: nginx
> image: nginx
> EOF
```
</b></details>

<details>
<summary>How to print information on a specific pod?</code></summary><br><b>

`kubectl describe pod pod_name`
</b></details>

<details>
<summary>How to delete a pod?</code></summary><br><b>
<summary>Deploy a pod called web-1985 using the nginx:alpine image</code></summary><br><b>

`kubectl delete pod pod_name`
</b></details>

<details>
<summary>How to check the status of all the components?</code></summary><br><b>
`kubectl run web-1985 --image=nginx:alpine --restart=Never`
</b></details>

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