DevOps Interview Questions and Answers 2019 | DevOps Tutorial | Edureka

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DevOps Interview Preparation 2019

DevOps Demands

DevOps Market
According to the “Global DevOps Platform Market 2016-2020”, created by the research firm Research and Markets, the
DevOps market should see a steady growth rate of around 20 percent (compound annual growth rate of 19.42%) through
the end of the decade.

Average Salary of a DevOps Practitioner
$50,000 - $75000$75,000 - $99,000
$100,000 - $125,000
$25,000
$75,000 - $99,999
$25,000
Team Size
Experience
$25,000
Source: https://puppet.com/resources/whitepaper/2016-state-of-devops-report

Enterprise Adoption Of DevOps
Source: http://rightscale7.rssing.com/chan-14813591/all_p7.html

DevOps Interview Questions

Classification Of DevOps Interview Questions
Generic DevOps Questions
Source Code Management Questions
Continuous Integration Questions
Configuration Management Questions
Continuous Monitoring Questions
Containerization And Virtualization Questions
Jenkins

Q1. What is DevOps?

Q1. What is DevOps?
Source Code
Management
Continuous
Integration
Continuous
Testing
Configuration
Management
Continuous
Monitoring

Q2. How is DevOps different from Agile?

Q2. How is DevOps different from Agile?
DevOps
Agile
Development Start Development End
Release Production Support
Development Operations
Testing

Q3. What is the need for DevOps?

Q3. What is the need for DevOps?
Increase
deployment
frequency
Lower
failure rate
of new
releases
Shortened
lead time
between
fixes
Faster mean
time to
recovery in
the event of
new release
failure

Q4. Name some top DevOps tools and how these tools work together?

Q4. Name some top DevOps tools and how these tools work together?
Production
Production
Production
Pulls the code
from Git
repository
Builds/Compile
the code
Test the build
software
Provisions the production and testing servers
Docker containers provide the consistent computing environment
throughout the SDLC

Source Code Management
Questions

Q5. What functions does Git performs in DevOps?

Q5. What functions does Git performs in DevOps?
Every time a commit is made in the Git repository, Continuous Integration server pulls it and
compiles it and also deploys it on the test server for testing

Q6. Explain Git’s distributed architecture?

Q6. Explain Git’s distributed architecture?
Collaborator
Remote
Repository
Local
Repo
Local
Repo
Local
Repo
Local
Repo
Local
Repo
Collaborator
Collaborator
CollaboratorCollaborator
Local
Repo
Collaborator
Commit changes
to source code
Commit changes
to source code
Commit changes
to source code
Commit changes
to source code
Commit changes
to source code
Commit changes
to source code

Q7. In Git how do you revert a commit that has already been pushed and made public?

Q7. In Git how do you revert a commit that has already been pushed and made public?
Remove or fix the bad file in a new commit and push it to the remote repository. This is the most natural
way to fix an error. Once you have made necessary changes to the file, commit it to the remote repository
for that I will use
git commit -m “commit message”
Create a new commit that undoes all changes that were made in the bad commit.to do this you can use a
command
git revert <name of bad commit>

Q8. How do you find a list of files that has changed in a particular commit?

Q8. How do you find a list of files that has changed in a particular commit?
To get a list files that has changed in a particular commit use the below command:
git diff-tree -r {hash}
Given the commit hash, this will list all the files that were changed or added in that commit. The -r flag makes
the command list individual files, rather than collapsing them into root directory names only.
The output will also include some extra information, which can be easily suppressed by including two flags:
git diff-tree –no-commit-id –name-only -r {hash}
Here –no-commit-id will suppress the commit hashes from appearing in the output, and –name-only will only
print the file names, instead of their paths.

Q9. How do you squash last N commits into a single commit?

Q9. How do you squash last N commits into a single commit?
There are two options to squash last N commits into a single commit:
❑ If you want to write the new commit message from scratch use the following command
git reset –soft HEAD~N &&
git commit
❑ If you want to start editing the new commit message with a concatenation of the existing commit messages then
you need to extract those messages and pass them to Git commit for that I will use
git reset –soft HEAD~N &&
git commit –edit -m”$(git log –format=%B –reverse .HEAD@{N})”

Q10. What is meant by Continuous Integration?

Q10. What is meant by Continuous Integration?
Commit Changes To
The Source Code
Build Test Deploy
Continuous
Integration
Server
Feedback

Q11. Mention some of the commonly used Jenkins Plugins

Plugin Feature
Git Plugin Git plugins are often used in projects to know whether the codes written are stable or not
SSH Plugin These plugin is used to run shell commands through SSH on a remote machine as they are
derived from SCP plugin
Build Pipeline Plugin This plugin provides a Build Pipeline View of upstream and downstream connected jobs that
typically form a build pipeline
Email-ext Plugin This plugin allows you to configure every aspect of email notifications. You can customize
when an email is sent, who should receive it, and what the email says
HTML Publisher Plugin This plugin publishes HTML reports
Multi-slave config Plugin This plugin allows administrators to configure, add and delete several dumb slaves at the
same time
Parameterized Trigger
Plugin
This plugin lets you trigger new builds when your build has completed, with various ways of
specifying parameters for the new build
Q11. Mention some of the commonly used Jenkins Plugins

Q12. Explain Jenkins distributed architecture and what is the need for this architecture?

Q12. Explain Jenkins distributed architecture and what is the need for this architecture?
The single Jenkins server was not enough to
meet certain requirements like:
❑ Sometimes you might need several different
environments to test your builds. This cannot
be done by a single Jenkins server
❑ If larger and heavier projects get built on a
regular basis then a single Jenkins server
cannot simply handle the entire load

Q13. How will you secure Jenkins?

Q13. How will you secure Jenkins?
❑ Ensure global security is on.
❑ Ensure that Jenkins is integrated with my company’s user directory with appropriate plugin.
❑ Ensure that matrix/Project matrix is enabled to fine tune access.
❑ Automate the process of setting rights/privileges in Jenkins with custom version controlled script.
❑ Limit physical access to Jenkins data/folders.
❑ Periodically run security audits on same.

Q14. Explain how you can create a backup and copy files in Jenkins?

Q14. Explain how you can create a backup and copy files in Jenkins?
This can be done by copying the jobs directory from the old server to the new one. There are multiple ways to do
that, you can:
❑ Move a job from one installation of Jenkins to another by simply copying the corresponding job directory.
❑ Make a copy of an existing job by making a clone of a job directory by a different name.
❑ Rename an existing job by renaming a directory. Note that if you change a job name you will need to change any
other job that tries to call the renamed job.

Configuration Management
Questions

Q15. Explain various Configuration Management components?

Q16. What is the difference between Asset management and Configuration Management?

Q17. What do you understand by “Infrastructure as code”?

Q17. What do you understand by “Infrastructure as code”?
DEV
TEST
PROD
IaC is automation of IT operations
(build, deploy, manage) by provisioning
of code , rather than manual process
Provisioning of Dev, Test and Prod environment
by writing code in one centralized location
Code for the
infrastructure

Q18. What is the difference between Push and Pull Configuration Management?

Q19. How Puppet works?

Q20. What are Modules and Manifests in Puppet?

Q20. What are Modules and Manifests in Puppet?
Puppet Module
A Puppet Module is a collection of Manifests and data
(such as facts, files, and templates), and they have a
specific directory structure. Modules are useful for
organizing your Puppet code, because they allow you to
split your code into multiple Manifests. Modules are self-
contained bundles of code and data.
You can find pre-defined modules at
forge.puppet.com/modules
Puppet Manifest
Every Slave has got its configuration details in Puppet
Master, written in the native Puppet language. These
details are written in the language which Puppet can
understand and are termed as Manifests. They are
composed of Puppet code and their filenames use
the .pp extension. These are basically Puppet programs.

Q21. Explain Chef Architecture

Q21. Explain Chef Architecture
❑ Chef Workstation: All the configurations
are first tested in the Workstation and
then pushed on the Chef Server
❑ Chef Server: It contains all the
Configurations which are pushed on the
Chef Nodes
❑ Chef Node: Nodes can be a cloud based
virtual server or a physical server in
your own data center, that is managed
using central Chef Server

Q22. Write a recipe to install httpd package and copy an index.html file to
the default document root to confirm the installation

Q22. Write a recipe to install httpd package and copy an index.html file to
the default document root to confirm the installation
A Recipe is a collection of resources that describes a particular configuration or policy. It describes everything that is
required to configure part of a system. The user writes Recipes that describe how Chef manages applications and utilities
(such as Apache HTTP Server, MySQL, or Hadoop) and how they are to be configured.

Q23. What happens when you don’t specify a Resource’s action in Chef?

Q23. What happens when you don’t specify a Resource’s action in Chef?
When you don’t specify a resource’s action, Chef applies the default action.
For ex:
the below resource:
is same as the below resource:
because: create is the file Resource’s default action.

Q24. Are these two Chef recipes the same?

Q24. Are these two Chef recipes the same?
No, they are not. Because Chef applies resources in the order they appear. So the first Recipe ensures that the httpd
package is installed and then configures the service. The second Recipe configures the service and then ensures the
package is installed.

Q25. Is Ansible a Push based or a pull based CM tool?

Q25. Is Ansible a Push based or a pull based CM tool?
Server
send specifications
poll for changes
1
2
Version Control System
Orchestrate (SSH)
3
Push Based

Q26. How does Ansible architecture looks like?

Modules APIs Plugins
Inventory
Hosts
CMDB
ANSIBLE AUTOMATION
ENGINE
PLAYBOOK
Q26. How does Ansible architecture looks like?

Q27. Why is Continuous Monitoring necessary?
Continuous Monitoring allows timely identification of problems or weaknesses in the software
and quick corrective action that helps reduce expenses of an organization.
Continuous monitoring provides solution that addresses three operational disciplines known as:
Continuous Audit
Continuous Controls Monitoring
Continuous Transaction Inspection

Q27. Why is Continuous Monitoring necessary?

Q28. How does Nagios work?

Q28. How does Nagios work?
❑ Nagios runs on a server, usually as a daemon or service. Nagios periodically runs plugins residing on the same server,
they contact hosts or servers on your network or on the internet. One can view the status information using the web
interface. You can also receive email or SMS notifications if something happens.
❑ The Nagios daemon behaves like a scheduler that runs certain scripts at certain moments. It stores the results of those
scripts and will run other scripts if these results change.

Q29. What is NRPE (Nagios Remote Plugin Executor) in Nagios?

Q29. What is NRPE (Nagios Remote Plugin Executor) in Nagios?
NRPE addon is designed to allow you to execute Nagios plugins on remote Linux/Unix machines. The main reason for doing
this is to allow Nagios to monitor “local” resources (like CPU load, memory usage, etc.) on remote machines.

Q30. When Does Nagios Check for external commands?

Q30. When Does Nagios Check for external commands?
Nagios check for external commands under the following conditions:
❑ At regular intervals specified by the command_check_interval option in the main configuration file or,
❑ Immediately after event handlers are executed. This is in addition to the regular cycle of external command checks
and is done to provide immediate action if an event handler submits commands to Nagios.

Q31. What is the difference between Active and Passive check in Nagios?

Q31. What is the difference between Active and Passive check in Nagios?
The major difference between Active and Passive checks is that Active checks are initiated and performed by Nagios,
while passive checks are performed by external applications.
Passive checks are useful for monitoring services that are:
❑ Asynchronous in nature and cannot be monitored effectively by polling their status on a regularly scheduled basis.
❑ Located behind a firewall and cannot be checked actively from the monitoring host.
The main features of Actives checks are as follows:
❑ Active checks are initiated by the Nagios process.
❑ Active checks are run on a regularly scheduled basis.

Q32. Explain how Flap Detection works in Nagios?

Q32. Explain how Flap Detection works in Nagios?
Storing the results of the last 21 checks of the host or service analyzing the historical
check results and determine where state changes/transitions occur.
Using the state transitions to determine a percent state change value (a measure of
change) for the host or service.
Comparing the percent state change value against low and high flapping thresholds
A host or service is determined to have started flapping when its percent state
change first exceeds a high flapping threshold.
A host or service is determined to have stopped flapping when its percent state
goes below a low flapping threshold.
Flapping occurs when a service or host changes state too frequently, this causes lot of problem and recovery notifications.
Whenever Nagios checks the status of a host or service, it will check to see if it has started or stopped flapping. Nagios
follows the below procedure to do that:

Containerization And Virtualization
Questions

Q33. What are Containers?

Q33. What are Containers?
A container consists of an entire runtime environment: an application, plus all its dependencies, libraries and other
binaries, and configuration files needed to run it, bundled into one package. Containerizing the application platform
and its dependencies removes the differences in OS distributions and underlying infrastructure.

Q35. Imagine a scenario when a large application is broken into smaller composable pieces and each of those
pieces have their own set of dependencies, let us call these pieces as Microservices. In order to run each of these
Microservices what will you use
1. Containers
2. Virtual Machines

Q35. Imagine a scenario when a large application is broken into smaller composable pieces and each of those
pieces have their own set of dependencies, let us call these pieces as Microservices. In order to run each of these
Microservices what will you use
1. Containers
2. Virtual Machines
Virtual Machines for
starting multiple
microservices
Developer’s
Laptop
Developer’s
Laptop
Virtual
Machine
Containers

Q36. Write a Dockerfile to create an Image to install MongoDB

Q36. Write a Dockerfile to create an Image to install MongoDB
FROM ubuntu #Set the base Image to Ubuntu
MAINTAINER Example McAuthor #File author / mantainer
RUN apt-get update #Update the repository sources list
#Add the package verification key
RUN apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
#Add MongoDB to the repository sources list
RUN echo 'deb http://downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | tee /etc/apt/sources.list.d/mongodb.list
#Update the repository sources list once more
RUN apt-get update
#Install MongoDB package
RUN apt-get install -y mongodb-10gen
#Create the default data directory
RUN mkdir -p /data/db
#Expose the default port
EXPOSE 27017
#Default port to execute the entrypoint (MongoDB)
CMD ["--port 27017"]
#Set default container command
ENTRYPOINT usr/bin/mongod

Q37. With an example, explain how Docker is used in SDLC?

Q37. With an example, explain how Docker is used in SDLC?
Docker
File Git Repo
Push the code
to Git Repo
Complex Requirements
for a microservice are
written in easy to write
DockerFile
Jenkins
Server
Production
Staging
Testing
• CI server pull it down and build the exact environment that will be used in production to run the test suite
without needing to configure the CI server at all.
• Deploy it out to a staging environment for testers.
• Roll exactly what you had in development, testing, and staging into production

Q38. How Docker provides consistent computing environment throughout the SDLC?

Q38. How Docker provides consistent computing environment throughout the SDLC?
Docker
File
Project Code
Docker Image
Docker
Container
Virtual Machine
Docker
Hub
Production
Server
Staging Server
Images
Images
❑ Docker file builds a Docker image and that image contains all the project's code
❑ You can run that image to create as many Docker containers as you want
❑ Then this Image can be uploaded on Docker hub, from Docker hub any one can pull the image and build a container

Q39. What is Docker Compose?

Q39. What is Docker Compose?
Docker Compose makes it easier to configure and run applications made up of multiple containers. For the example:
imagine being able to define three containers—one running a web app, another running postgres, and a third running
redis—all in one YAML file and then running those three connected containers with a single command.
web app
postgres
redis
Docker
Compose
File
You can run these three containers
with a single command
Containers

Session In A Minute
Generic Devops Questions Source Code Management Questions
Configuration Management Questions Continuous Monitoring Questions
Containerization and Virtualization Questions

Thank You …
Questions/Queries/Feedback

DevOps Interview Questions and Answers 2019 | DevOps Tutorial | Edureka

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