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devops/SRE interview questions

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# Devops/SRE interview preparation questions
This repo is aggregated guide for preparation to Devops/SRE engineer interview
#### If you want to thank the author https://www.buymeacoffee.com/mikonoid

## Linux

<details>
<summary>History of OS</summary> 
Explanation: https://www.geeksforgeeks.org/evolution-of-operating-system/
</details>

<details>
<summary>What is Linux Standard Base?</summary> 
Explanation: https://en.wikipedia.org/wiki/Linux_Standard_Base
</details>

<details>
<summary>Popular Linux Distributions</summary> 
The most popular linux distros:

* Ubuntu
  * Centos
  * Fedora
  * Debian
  * OpenSuse
  * ArchLinux
  * Slackware

Comparison: https://www.howtogeek.com/191207/10-of-the-most-popular-linux-distributions-compared/

</details>

<details>
<summary>Linux boot process: from power up to login prompt</summary> 
Explanation:

* BIOS
  * MBR
  * GRUB
  * Kernel
  * Init
  * Runlevel

https://www.thegeekstuff.com/2011/02/linux-boot-process/
</details>

<details>
<summary>What is inode?</summary> 
Explanation: https://linoxide.com/linux-command/linux-inode/
</details>

<details>
<summary>Memory types in Linux</summary>

Explanation: https://linux-audit.com/understanding-memory-information-on-linux-systems/
</details>

<details>
<summary>What is sticky bit?</summary> 
Explanation:

* https://en.wikipedia.org/wiki/Sticky_bit
 * https://www.geeksforgeeks.org/setuid-setgid-and-sticky-bits-in-linux-file-permissions/
</details>

<details>
<summary>What is Virtual memory?</summary> 
Explanation:

* https://serverfault.com/questions/138427/what-does-virtual-memory-size-in-top-mean
 * https://elinux.org/images/4/4c/Ott.pdf
</details>

<details>
<summary>What is a swap space?</summary>

Explanation: https://itsfoss.com/create-swap-file-linux/
</details>

<details>
<summary>What is zombie process?</summary> 
Explanation:

* https://en.wikipedia.org/wiki/Zombie_process
 * https://www.geeksforgeeks.org/zombie-processes-prevention/
 * https://stackoverflow.com/questions/16944886/how-to-kill-zombie-process
</details>

<details>
<summary>File types in Linux</summary> 
Explanation:
 https://www.linux.com/tutorials/file-types-linuxunix-explained-detail/
</details>

<details>
<summary> What is proc filesystem?</summary> 
Explanation:

http://man7.org/linux/man-pages/man5/proc.5.html
 https://docs.kernel.org/filesystems/proc.html
</details>

<details>
<summary>Linux Process Monitor(TOP). Explain all information from top</summary> 
Explanation:

https://www.maketecheasier.com/linux-top-explained/
</details>

<details>
<summary>What is the difference between hardlinks and symlinks?</summary> 
Explanation:

https://medium.com/@307/hard-links-and-symbolic-links-a-comparison-7f2b56864cdd
</details>

<details>
<summary>What happens if you delete the root user?</summary> 
Explanation:

* In most cases you will get unbootable system
 * https://askubuntu.com/questions/962660/what-happens-if-you-delete-the-root-user
</details>

<details>
<summary>What is a chroot?</summary> 
Explanation:

https://www.howtogeek.com/441534/how-to-use-the-chroot-command-on-linux/
</details>

<details>
<summary>What is OOM and OOMkiller? How it OOM killer is working</summary> 
Explanation:

* https://dev.to/rrampage/surviving-the-linux-oom-killer-2ki9
 * https://www.percona.com/blog/2019/08/02/out-of-memory-killer-or-savior/
</details>

<details>
<summary>What is kernel panic?</summary> 
Explanation:

* https://www.linuxjournal.com/content/oops-debugging-kernel-panics-0
 * http://www.linuxandubuntu.com/home/things-to-know-about-linux-kernel-panic
</details>

<details>
<summary>What is 'nohup' used for?</summary> 
Explanation:

https://www.computerhope.com/unix/unohup.htm
</details>

<details>
<summary> What can you do to restore deleted bash script(script is running but deleted by error)?</summary> 
Explanation:

See filesystem /proc and find ID proccess in that directory should be script
</details>

<details>
<summary> What is RAID?</summary> 
Explanation:

https://en.wikipedia.org/wiki/Standard_RAID_levels
</details>

<details>
<summary>What happens when a hardlink is removed?</summary> 
Explanation:

The file will be deleted if you delete only the last hardlink to this file.
</details>

<details>
<summary>Imagine you executed command `chmod -x /bin/chmod`. How to fix this? </summary> 
Explanation:

Solution1:
  ```
  cp /bin/cp /tmp/chmod
  cp /bin/chmod /tmp/chmod
  ./tmp/chmod 755 /bin/chmod

```

Solution2:
  ```
  perl -e 'chmod(0755, "chmod")`

```

Solution3:
  ```
 /lib/ld-linux.so.2 /bin/chmod 755 /bin/chmod

```

</details>

<details>
<summary>What is Load Average?</summary> 
Explanation:

http://www.brendangregg.com/blog/2017-08-08/linux-load-averages.html
</details>

<details>
<summary>What are cgroups?</summary> 
Explanation:

https://www.linuxjournal.com/content/everything-you-need-know-about-linux-containers-part-i-linux-control-groups-and-process
</details>

## Networking and Security

<details>
<summary>What is NAT?</summary> 
Explanation:

* https://www.geeksforgeeks.org/network-address-translation-nat/
 * https://www.comptia.org/content/guides/what-is-network-address-translation
</details>

<details>
<summary>What is VLAN?</summary> 
Explanation:

https://study-ccna.com/what-is-a-vlan/
</details>

<details>
<summary>What is ARP?</summary> 
Explanation:

Address Resolution Protocol.
 https://en.wikipedia.org/wiki/Address_Resolution_Protocol
</details>

<details>
<summary> How many layers are there under TCP/IP? Compare OSI and TCP/IP</summary> 
Explanation:

https://techdifferences.com/difference-between-tcp-ip-and-osi-model.html
</details>

<details>
<summary>Explain TCP 3-way handshake process</summary> 
Explanation:

https://www.geeksforgeeks.org/tcp-3-way-handshake-process/
</details>

<details>
<summary>What is SSH and how does it work?</summary> 
Explanation:

https://www.ssh.com/ssh/command
</details>

<details>
<summary>Explain DNS records: SOA, PTR, A, MX, and CNAME</summary> 
Explanation:

https://www.presslabs.com/how-to/dns-records/
</details>

<details>
<summary>How to check route table in Linux?</summary> 
Explanation:

`netstat -rn`

`route -n`

`ip route list`
</details>

<details>
<summary>Server1 can't reach to Server2. Describe possible reasons</summary> 
Explanation:

* Application layer:
 Check if servers are correctly configured and services up and running
 * Transport layer:
 Check ports, check ping from server to server
 * Network layer:
 Check firewall and networking setting. Also check routes, dns and ARP tables.
</details>

<details>
<summary>How to check all of open ports on server?</summary> 
Explanation:

* nmap - if you need check all ports for remote server
 * netstat - for localhost
</details>

## Programming

### BASH

<details>
<summary>How to check if the last command was run successfully?</summary> 
Explanation:

`echo $?` if returns 0 that last command executed successfully

</details>

<details>
<summary>What is function? How to write a function?</summary> 
Explanation:

https://linuxize.com/post/bash-functions/
</details>

<details>
<summary>Loops in BASH</summary> 
Explanation:

https://www.tldp.org/HOWTO/Bash-Prog-Intro-HOWTO-7.html
</details>

<details>
<summary> How would you compare two strings in a bash script?</summary> 
Explanation:
 Case1:

```
  #!/bin/bash

VAR1="string1"
VAR2="string333"

if [ "$VAR1" = "$VAR2" ]; then
    echo "Strings are equal."
else
    echo "Strings are not equal."
fi
```
  Case2:

```
  [[ "string1" == "string2" ]] && echo "Equal" || echo "Not equal"

```

</details>

<details>
<summary> How to print all array elements and their indexes?</summary> 
Explanation:

```
  #!/bin/bash
  array=("A" "B" "C" "X" )
  echo ${array[0]}

```

</details>

<details>
<summary>Print number from 1 to 10 using for loop</summary> 
Explanation:

```
  #!/bin/bash
  for i in {1..10}; do
      echo $i
  done

```

</details>

<details>
<summary>How to debug a shell script ?</summary> 
Explanation:

Option `-x`
 or `-nv`
</details>

### Python
<details>
<summary>Python for sysadmins</summary> 
Explanation:

* https://realpython.com/
 * https://python-for-system-administrators.readthedocs.io/en/latest/
</details>

<details>
<summary>How to compile python application?</summary> 
Explanation:

There are two ways could go about to solve that problem:

* Use a static builder, like freeze, or pyinstaller, or py2exe
* Compile using cython
</details>

<details>
<summary>What is PEP 8 and why is it important?</summary> 
Explanation:

* https://realpython.com/python-pep8/

</details>

## Databases

<details>
<summary>What is SQL?</summary> 
Explanation:
 * http://www.sqlcourse.com/intro.html
</details>

<details>
<summary>SQL vs NoSQL. Explain benefits of both</summary> 
Explanation:

* https://www.youtube.com/watch?v=ZS_kXvOeQ5Y
 * https://www.geeksforgeeks.org/difference-between-sql-and-nosql/
</details>

<details>
<summary>What are tables and field?</summary> 
Explanation:

* https://intellipaat.com/blog/tutorial/sql-tutorial/tables-in-sql/
</details>

<details>
<summary>What is an index?</summary> 
Explanation:
 * https://www.tutorialspoint.com/sql/sql-indexes.htm
</details>

<details>
<summary>What is primary key?</summary> 
Explanation:
 * https://www.w3schools.com/sql/sql_primarykey.ASP
</details>

<details>
<summary>What is database replication?</summary> 
Explanation:

* https://www.geeksforgeeks.org/data-replication-in-dbms/
</details>

<details>
<summary>What is DynamoDB?</summary> 
Explanation:

* https://www.dynamodbguide.com/what-is-dynamo-db/
</details>

## Version Control System (GIT)

<details>
<summary>What is GIT?</summary> 
Explanation:

* https://git-scm.com/book/en/v2/Getting-Started-What-is-Git

</details>

<details>
<summary> What are the benefits of using GIT?</summary> 
Explanation:

* Documentation
  * Markdown
  * Fully Distributed
  * Simplicity
  * Branching model
  * open source

</details>

<details>
<summary>What is the difference between `git pull` and `git fetch` ?</summary> 
Explanation:

* https://guide.freecodecamp.org/miscellaneous/git-pull-vs-git-fetch/

</details>

<details>
<summary>What is the difference between `git reset` and `git revert` ?</summary> 
Explanation:

* https://stackoverflow.com/questions/8358035/whats-the-difference-between-git-revert-checkout-and-reset

</details>

<details>
<summary>What is `git rebase` ?</summary> 
Explanation:

* https://www.atlassian.com/git/tutorials/rewriting-history/git-rebase

</details>

<details>
<summary>How to reset last commit?</summary> 
Explanation:

* `git reset --hard HEAD~1` - not a true way cuz you will lost all changes
 * `git revert <commit-id>` - good way

for more https://stackoverflow.com/questions/927358/how-do-i-undo-the-most-recent-local-commits-in-git

</details>

<details>
<summary>Describe a dev/test/production workflow using GIT</summary> 
Explanation:

* https://medium.com/@patrickporto/4-branching-workflows-for-git-30d0aaee7bf
  * https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow

</details>

## Containers

<details>
<summary>History of containers</summary> 
Explanation:

* https://www.aquasec.com/blog/a-brief-history-of-containers-from-1970s-chroot-to-docker-2016/
  * https://www.pluralsight.com/resources/blog/cloud/history-of-container-technology

</details>

<details>
<summary>What is LXC?</summary> 
Explanation:

* https://linuxcontainers.org/lxc/introduction/

</details>

<details>
<summary>What is Docker?</summary> 
Explanation:

* https://opensource.com/resources/what-docker

</details>

<details>
<summary>What are the advantages of using Docker container?</summary> 
Explanation:

* https://dzone.com/articles/top-10-benefits-of-using-docker

</details>

<details>
<summary>Docker RUN vs CMD vs ENTRYPOINT</summary> 
Explanation:

* https://goinbigdata.com/docker-run-vs-cmd-vs-entrypoint/

</details>

<details>
<summary>What is the difference between ADD and COPY in Dockerfile?</summary> 
Explanation:
 * https://dev.to/lasatadevi/docker-cmd-vs-entrypoint-34e0
</details>

<details>
<summary>What is Docker registry?</summary> 
Explanation:

Storage for docker images https://docs.docker.com/registry/

</details>

<details>
<summary>What is Docker volume?</summary> 
Explanation:

* https://docs.docker.com/storage/volumes/

</details>

<details>
<summary>What is docker namespaces?</summary> 
Explanation:

* https://success.docker.com/article/introduction-to-user-namespaces-in-docker-engine

</details>

<details>
<summary>Docker and OCI</summary> 
Explanation:

* https://www.padok.fr/en/blog/container-docker-oci

</details>

<details>
<summary>What is docker multistage build? Create one example</summary> 
Explanation:

* https://dev.to/brpaz/using-docker-multi-stage-builds-during-development-35bc

</details>

## Kubernetes

<details>
<summary>Why we need container orchestration?</summary> 
Explanation:

* https://opensource.com/life/16/9/containing-container-chaos-kubernetes
</details>

<details>
<summary>What is kubernetes?</summary> 
Explanation:
 TODO
</details>

<details>
<summary>What are the features of Kubernetes?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/
 * Kubernetes in 5 minutes https://www.youtube.com/watch?v=PH-2FfFD2PU
</details>

<details>
<summary>What is POD?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/workloads/pods/pod/
</details>

<details>
<summary>What is kubelet?</summary> 
Explanation:
 * Kubelet - agent on a kubernetes cluster’s node that takes care of all activity on that node
 * https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/
</details>

<details>
<summary>What is kubectl?</summary> 
Explanation:

* https://kubernetes.io/docs/reference/kubectl/overview/
</details>

<details>
<summary>What is CNI?</summary> 
Explanation:

* https://www.dasblinkenlichten.com/understanding-cni-container-networking-interface/
</details>

<details>
<summary>What is headless service?</summary> 
Explanation:

* https://dev.to/kaoskater08/building-a-headless-service-in-kubernetes-3bk8
</details>

<details>
<summary>What are the units of CPU and memory in POD definition?</summary> 
Explanation:

* CPU is in milicores and memory in bytes
 * https://www.noqcks.io/notes/2018/02/03/understanding-kubernetes-resources/
</details>

<details>
<summary>How to deploy stateful application in Kubernetes?</summary> 
Explanation:

* https://cloud.google.com/kubernetes-engine/docs/how-to/stateful-apps
 * https://kubernetes.io/docs/tasks/run-application/run-replicated-stateful-application/
</details>

<details>
<summary>How to expose Kubernetes service?</summary> 
Explanation:
 * https://kubernetes.io/docs/tutorials/kubernetes-basics/expose/expose-intro/
</details>

<details>
<summary>Kubernetes deployments strategies: blue-green, canary, rolling</summary> 
Explanation:
 * https://traefik.io/glossary/kubernetes-deployment-strategies-blue-green-canary/
</details>

<details>
<summary>Kubernetes etcd. How to backup etcd.</summary> 
Explanation:
 * https://medium.com/@mehmetodabashi/backup-and-restore-etcd-cluster-on-kubernetes-93c19b1c070
 * https://kubernetes.io/docs/tasks/administer-cluster/configure-upgrade-etcd/
</details>

<details>
<summary>Custom Resource Definitions (CRD)</summary> 
Explanation:
 * https://spacelift.io/blog/kubernetes-crd
 * https://kubernetes.io/docs/concepts/extend-kubernetes/api-extension/custom-resources/
</details>

<details>
<summary>NodePort vs ClusterIP</summary> 
Explanation:
 * https://edgedelta.com/company/blog/kubernetes-services-types
 * https://kubernetes.io/docs/tutorials/kubernetes-basics/expose/expose-intro/
</details>

## DEVOPS

### 12 Factors App

<details>
<summary>What is 12 Factor App methodology?</summary> 
Explanation:

The 12 Factor App is a methodology for building software-as-a-service applications created by developers at Heroku. It provides best practices for building modern, scalable, maintainable applications.

* https://12factor.net/
</details>

<details>
<summary>What are the 12 factors?</summary> 
Explanation:

1. **Codebase** - One codebase tracked in version control, many deploys
  2. **Dependencies** - Explicitly declare and isolate dependencies
  3. **Config** - Store config in the environment
  4. **Backing Services** - Treat backing services as attached resources
  5. **Build, Release, Run** - Strictly separate build and run stages
  6. **Processes** - Execute the app as one or more stateless processes
  7. **Port Binding** - Export services via port binding
  8. **Concurrency** - Scale out via the process model
  9. **Disposability** - Maximize robustness with fast startup and graceful shutdown
  10. **Dev/Prod Parity** - Keep development, staging, and production as similar as possible
  11. **Logs** - Treat logs as event streams
  12. **Admin Processes** - Run admin/management tasks as one-off processes

* https://12factor.net/
</details>

<details>
<summary>Why is 12 Factor App important for DevOps?</summary> 
Explanation:

The 12 Factor methodology aligns perfectly with DevOps principles:
  * Enables continuous deployment and delivery
  * Makes applications cloud-native and container-ready
  * Ensures portability between environments
  * Facilitates horizontal scaling
  * Improves maintainability and reduces technical debt
  * Supports automation and infrastructure as code

* https://www.redhat.com/en/topics/cloud-native-apps
 * https://12factor.net/
</details>

<details>
<summary>Explain Factor III: Config - Store config in the environment</summary> 
Explanation:

Applications should store configuration in environment variables, not in code. This includes:
  * Database credentials
  * API keys and secrets
  * Hostnames for external services
  * Per-deploy values

Benefits:
  * Easy to change configuration without changing code
  * Configuration is not accidentally committed to version control
  * Works well with containers and orchestration systems

* https://12factor.net/config
</details>

<details>
<summary>Explain Factor VI: Processes - Execute the app as stateless processes</summary> 
Explanation:

Applications should be stateless and share-nothing. Any data that needs to persist must be stored in a stateful backing service (database, cache).

Benefits:
  * Enables horizontal scaling
  * Makes applications resilient to failures
  * Simplifies deployment and rollback
  * Works well with container orchestration (Kubernetes)

* https://12factor.net/processes
</details>

<details>
<summary>Explain Factor X: Dev/Prod Parity - Keep environments similar</summary> 
Explanation:

Keep development, staging, and production environments as similar as possible:
  * **Time gap** - Deploy code quickly (hours, not weeks)
  * **Personnel gap** - Developers deploy their own code
  * **Tools gap** - Use same tools/services in all environments

Benefits:
  * Reduces bugs from environment differences
  * Enables continuous deployment
  * Improves developer confidence
  * Containers and IaC help achieve this

* https://12factor.net/dev-prod-parity
</details>

<details>
<summary>Explain Factor XI: Logs - Treat logs as event streams</summary> 
Explanation:

Applications should not manage log files. Instead, write all logs to stdout as a stream of events.

Benefits:
  * Simplifies application code
  * Enables centralized log aggregation (ELK, Splunk)
  * Works well with container orchestration
  * Logs can be routed to multiple destinations

Tools: Fluentd, Logstash, CloudWatch, Datadog

* https://12factor.net/logs
</details>

<details>
<summary>How do containers and Kubernetes support 12 Factor App?</summary> 
Explanation:

Containers and Kubernetes are perfect for 12 Factor Apps:
  * **Codebase** - Dockerfile in Git repository
  * **Dependencies** - Isolated in container image
  * **Config** - ConfigMaps and Secrets
  * **Backing Services** - Services and external resources
  * **Build/Release/Run** - CI/CD pipelines with container registries
  * **Processes** - Pods are ephemeral and stateless
  * **Port Binding** - Services expose ports
  * **Concurrency** - Horizontal Pod Autoscaler
  * **Disposability** - Quick startup, graceful shutdown
  * **Dev/Prod Parity** - Same container in all environments
  * **Logs** - Container logs to stdout
  * **Admin Processes** - Jobs and CronJobs

* https://kubernetes.io/docs/concepts/
</details>

### Config management

<details>
<summary>Ansible tutorials</summary> 
Explanation:

* Ansible for Devops https://leanpub.com/ansible-for-devops
 * https://serversforhackers.com/c/an-ansible-tutorial
 * https://medium.com/quick-code/top-tutorials-to-learn-ansible-33afd23ea160
</details>

<details>
<summary>Salt tutorials</summary> 
Explanation:

* https://docs.saltstack.com/en/master/topics/tutorials/walkthrough.html
 * https://www.digitalocean.com/community/tutorials/an-introduction-to-saltstack-terminology-and-concepts
</details>

<details>
<summary>Puppet tutorials</summary> 
Explanation:

* https://www.guru99.com/puppet-tutorial.html
</details>

### CI/CD

<details>
<summary>What is continuous integration?</summary> 
Explanation:

* https://www.youtube.com/watch?v=_zCyLT33moA
 * https://www.atlassian.com/continuous-delivery/continuous-integration
</details>

<details>
<summary>What is continuous delivery?</summary> 
Explanation:

* https://www.atlassian.com/continuous-delivery/principles/continuous-integration-vs-delivery-vs-deployment
 * https://aws.amazon.com/devops/continuous-delivery/
</details>

<details>
<summary>What is continuous deployment?</summary> 
Explanation:

* https://www.atlassian.com/continuous-delivery/continuous-deployment
</details>

<details>
<summary>What are the benefits of CI/CD?</summary> 
Explanation:

* https://www.katalon.com/resources-center/blog/benefits-continuous-integration-delivery/
</details>

<details>
<summary>Describe a simple CI/CD Pipeline</summary> 
Explanation:

https://semaphoreci.com/cicd
 https://www.redhat.com/en/topics/devops/what-is-ci-cd
</details>

<details>
<summary>Describe deployment strategies</summary> 
Explanation:

https://thenewstack.io/deployment-strategies
</details>

<details>
<summary>Jenkins tutorials</summary> 
Explanation:

* https://www.udemy.com/share/101WuI/
  * https://www.youtube.com/playlist?list=PL9ooVrP1hQOGM6eCsjnfAousUSvpqD8dW&ref=hackr.io
  * https://jenkins.io/doc/book/

</details>

<details>
<summary>K8S native CI/CD</summary> 
Explanation:

* Tekton https://github.com/tektoncd
  * ArgoCD https://argoproj.github.io/argo-cd/
  * JenkinsX https://jenkins-x.io/

</details>

### Containerization & Orchestration

<details>
<summary>What is a container? How does it differ from a VM?</summary> 
Explanation:

* https://www.docker.com/resources/what-container
 * https://www.backblaze.com/blog/vm-vs-containers/
</details>

<details>
<summary>What is Docker?</summary> 
Explanation:

* https://docs.docker.com/get-started/overview/
 * https://www.redhat.com/en/topics/containers/what-is-docker
</details>

<details>
<summary>Explain Docker architecture</summary> 
Explanation:

* Docker daemon, Docker client, Docker registry
 * https://docs.docker.com/get-started/overview/#docker-architecture
</details>

<details>
<summary>What is the difference between Docker image and container?</summary> 
Explanation:

* Image is a template, container is a running instance
 * https://stackoverflow.com/questions/23735149/what-is-the-difference-between-a-docker-image-and-a-container
</details>

<details>
<summary>What is Dockerfile? Explain best practices</summary> 
Explanation:

* https://docs.docker.com/engine/reference/builder/
 * https://docs.docker.com/develop/dev-best-practices/
</details>

<details>
<summary>What is Docker Compose?</summary> 
Explanation:

* https://docs.docker.com/compose/
</details>

<details>
<summary>Docker multi-stage builds</summary> 
Explanation:

* https://docs.docker.com/build/building/multi-stage/
</details>

<details>
<summary>What is Kubernetes?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/
</details>

<details>
<summary>Kubernetes architecture (Control Plane, Worker Nodes)</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/architecture/
</details>

<details>
<summary>What are Kubernetes pods, deployments, services, ingress?</summary> 
Explanation:

* Pods: https://kubernetes.io/docs/concepts/workloads/pods/
 * Deployments: https://kubernetes.io/docs/concepts/workloads/controllers/deployment/
 * Services: https://kubernetes.io/docs/concepts/services-networking/service/
 * Ingress: https://kubernetes.io/docs/concepts/services-networking/ingress/
</details>

<details>
<summary>What is a namespace in Kubernetes?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/overview/working-with-objects/namespaces/
</details>

<details>
<summary>ConfigMaps and Secrets in Kubernetes</summary> 
Explanation:

* ConfigMaps: https://kubernetes.io/docs/concepts/configuration/configmap/
 * Secrets: https://kubernetes.io/docs/concepts/configuration/secret/
</details>

<details>
<summary>What are StatefulSets and when to use them?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/
</details>

<details>
<summary>What is a DaemonSet?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/
</details>

<details>
<summary>Kubernetes persistent volumes and storage classes</summary> 
Explanation:

* PV: https://kubernetes.io/docs/concepts/storage/persistent-volumes/
 * Storage Classes: https://kubernetes.io/docs/concepts/storage/storage-classes/
</details>

<details>
<summary>What is Helm?</summary> 
Explanation:

* https://helm.sh/docs/
 * https://www.redhat.com/en/topics/devops/what-is-helm
</details>

<details>
<summary>Kubernetes resource limits and requests</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/configuration/manage-resources-containers/
</details>

<details>
<summary>Kubernetes networking model</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/cluster-administration/networking/
</details>

<details>
<summary>What are init containers?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/workloads/pods/init-containers/
</details>

<details>
<summary>Kubernetes probes (liveness, readiness, startup)</summary> 
Explanation:

* https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/
</details>

### Monitoring & Logging

<details>
<summary>What is observability?</summary> 
Explanation:

* https://www.ibm.com/cloud/learn/observability
 * Three pillars: metrics, logs, traces
</details>

<details>
<summary>What is Prometheus?</summary> 
Explanation:

* https://prometheus.io/docs/introduction/overview/
</details>

<details>
<summary>Prometheus architecture and components</summary> 
Explanation:

* https://prometheus.io/docs/introduction/overview/#architecture
</details>

<details>
<summary>What is Grafana?</summary> 
Explanation:

* https://grafana.com/docs/grafana/latest/introduction/
</details>

<details>
<summary>ELK Stack (Elasticsearch, Logstash, Kibana)</summary> 
Explanation:

* https://www.elastic.co/what-is/elk-stack
</details>

<details>
<summary>What is distributed tracing? Jaeger, Zipkin</summary> 
Explanation:

* https://opentelemetry.io/docs/concepts/observability-primer/#distributed-traces
 * Jaeger: https://www.jaegertracing.io/
 * Zipkin: https://zipkin.io/
</details>

<details>
<summary>Log aggregation vs log streaming</summary> 
Explanation:

* Fluentd, Fluent Bit, Logstash comparison
 * https://logz.io/blog/fluentd-logstash/
</details>

<details>
<summary>What are SLI, SLO, SLA?</summary> 
Explanation:

* https://cloud.google.com/blog/products/devops-sre/sre-fundamentals-slis-slas-and-slos
 * https://sre.google/sre-book/service-level-objectives/
</details>

<details>
<summary>What is APM (Application Performance Monitoring)?</summary> 
Explanation:

* https://www.dynatrace.com/news/blog/what-is-apm-2/
 * Tools: New Relic, Datadog, Dynatrace
</details>

### GitOps

<details>
<summary>What is GitOps?</summary> 
Explanation:

* https://www.gitops.tech/
 * https://www.weave.works/technologies/gitops/
</details>

<details>
<summary>GitOps tools (ArgoCD, Flux)</summary> 
Explanation:

* ArgoCD: https://argo-cd.readthedocs.io/en/stable/
 * Flux: https://fluxcd.io/
</details>

### Security & Compliance

<details>
<summary>What is DevSecOps?</summary> 
Explanation:

* https://www.redhat.com/en/topics/devops/what-is-devsecops
</details>

<details>
<summary>Container security scanning (Trivy, Clair, Aqua)</summary> 
Explanation:

* Trivy: https://github.com/aquasecurity/trivy
 * https://sysdig.com/learn-cloud-native/kubernetes-security/kubernetes-image-scanning/
</details>

<details>
<summary>What is SAST and DAST?</summary> 
Explanation:

* https://www.synopsys.com/glossary/what-is-sast.html
 * https://www.microfocus.com/en-us/what-is/dast
</details>

<details>
<summary>Secret management (HashiCorp Vault, AWS Secrets Manager)</summary> 
Explanation:

* Vault: https://www.vaultproject.io/
 * AWS Secrets Manager: https://aws.amazon.com/secrets-manager/
</details>

<details>
<summary>What is RBAC in Kubernetes?</summary> 
Explanation:

* https://kubernetes.io/docs/reference/access-authn-authz/rbac/
</details>

<details>
<summary>What are admission controllers in Kubernetes?</summary> 
Explanation:

* https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/
</details>

<details>
<summary>Network policies in Kubernetes</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/services-networking/network-policies/
</details>

<details>
<summary>What is Pod Security Policy/Pod Security Standards?</summary> 
Explanation:

* https://kubernetes.io/docs/concepts/security/pod-security-standards/
</details>

### Version Control & Collaboration

<details>
<summary>Git branching strategies (GitFlow, trunk-based)</summary> 
Explanation:

* https://www.atlassian.com/git/tutorials/comparing-workflows/gitflow-workflow
 * https://trunkbaseddevelopment.com/
</details>

<details>
<summary>What is monorepo vs polyrepo?</summary> 
Explanation:

* https://www.atlassian.com/git/tutorials/monorepos
</details>

<details>
<summary>Code review best practices</summary> 
Explanation:

* https://google.github.io/eng-practices/review/
</details>

### Service Mesh

<details>
<summary>What is a service mesh?</summary> 
Explanation:

* https://www.redhat.com/en/topics/microservices/what-is-a-service-mesh
</details>

<details>
<summary>Istio overview</summary> 
Explanation:

* https://istio.io/latest/docs/concepts/what-is-istio/
</details>

<details>
<summary>Linkerd overview</summary> 
Explanation:

* https://linkerd.io/
</details>

### Chaos Engineering

<details>
<summary>What is Chaos Engineering?</summary> 
Explanation:

* https://principlesofchaos.org/
 * https://www.gremlin.com/community/tutorials/chaos-engineering-the-history-principles-and-practice/
</details>

<details>
<summary>Chaos Engineering tools (Chaos Monkey, Gremlin, Litmus)</summary> 
Explanation:

* Chaos Monkey: https://netflix.github.io/chaosmonkey/
 * Gremlin: https://www.gremlin.com/
 * Litmus: https://litmuschaos.io/
</details>

### Infrastructure as code

#### Terraform questions

<details>
<summary>Terraform tutorials</summary> 
Explanation:

* https://www.youtube.com/watch?v=TFLQcgZr0no
  * https://www.udemy.com/share/101ZdI/
  * https://itnext.io/terraform-tutorial-part-1-intro-and-basic-concepts-7a27ae7722b6

</details>

<details>
<summary>What is terraform modules?</summary> 
Explanation:

* https://www.freecodecamp.org/news/terraform-modules-explained/

</details>

<details>
<summary>What is ".terraform" directory?</summary> 
Explanation:

```The ".terraform" directory is a local cache where Terraform retains some files required for subsequent operations against this configuration. Its contents are not intended to be included in version control.```

</details>

<details>
<summary>What is the usage of Terraform init?</summary> 
Explanation:

```Terraform init is a command used to initialize the Terraform code. Let's see the all usage of Terraform init command:

* Terraform init command is used to initialize the working directory containing Terraform configuration files.
* It is used for Plugin Installation.
* It is also used for Child Module Installation.
* It is used for Backend Initialization.
* You can safely run this command multiple times.
```

</details>

<details>
<summary>What do you understand by Terraform Backends? What are the most recommended Backends we should use?</summary> 
Explanation:

```Terraform backends are used to define where and how operations are performed, where state snapshots are stored, etc. Each Terraform configuration can specify a backend.```

Reference:
* https://developer.hashicorp.com/terraform/language/settings/backends/configuration

</details>

<details>
<summary>What is terraform lock file?</summary>

Explanation:

* https://developer.hashicorp.com/terraform/language/files/dependency-lock

</details>

#### AWS Cloudformation

<details>
<summary>AWS CloudFormation</summary>

Explanation:

* https://www.youtube.com/watch?v=0Sh9OySCyb4
  * https://www.simplilearn.com/tutorials/aws-tutorial/aws-cloudformation

</details>

### Clouds

<details>
<summary>What is PaaS, SaaS, IaaS?</summary> 
Explanation:

* https://www.ibm.com/cloud/learn/iaas-paas-saas
</details>

<details>
<summary>What is private cloud?</summary> 
Explanation:

* https://azure.microsoft.com/en-us/overview/what-are-private-public-hybrid-clouds/
</details>

<details>
<summary>What is public cloud?</summary> 
Explanation:

* https://azure.microsoft.com/en-us/overview/what-is-a-public-cloud/
 * examples: AWS, GCP, DegitalOcean, Azure
</details>

<details>
<summary>What is cloud service?</summary> 
Explanation:

* https://searchitchannel.techtarget.com/definition/cloud-services
</details>

<details>
<summary>What is serverless service?</summary> 
Explanation:

* https://en.wikipedia.org/wiki/Serverless_computing
</details>

<details>
<summary>AWS tutorials</summary> 
Explanation:

* https://medium.com/javarevisited/5-best-aws-courses-for-beginners-and-experienced-developers-to-learn-in-2021-563212409fbd
 * https://docs.aws.amazon.com/
</details>

<details>
<summary>Google Cloud tutorials</summary> 
Explanation:

* https://www.udemy.com/topic/google-cloud/
 * https://linuxacademy.com/course/google-cloud-data-engineer/
</details>

<details>
<summary>Openstack tutorials</summary> 
Explanation:

The best resource with Openstack cources is LinuxAcademy
 https://linuxacademy.com/library/search/openstack/
</details>

## Books and courses

* Brendan Gregg http://www.brendangregg.com/blog/index.html
* Systems Performance http://www.brendangregg.com/sysperfbook.html
* The Phoenix project https://www.amazon.com/Phoenix-Project-DevOps-Helping-Business/dp/1942788290/
* SRE https://landing.google.com/sre/books/
* Linux System Administration Handbook 5th by Evi Nemeth
* The DevOps Handbook: How to Create World-Class Agility, Reliability, and Security in Technology Organizations
* Continuous Delivery: Reliable Software Releases through Build, Test, and Deployment Automation by Jez Humble and David Farley

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