DevOps Interview Questions

1. State file in Terraform?

Terraform must store state about your managed infrastructure and configuration, is used by Terraform to map real-world resources to your configuration, keep track of metadata, and to improve performance for large infrastructures.

This state is stored by default in a local file named "terraform.tfstate", but it can also be stored remotely, which works better in a team environment.

primary purpose of Terraform state is to store bindings between objects in a remote system and resource instances declared in your configuration. When Terraform creates a remote object in response to a change of configuration, it will record the identity of that remote object against a particular resource instance, and then potentially update or delete that object in response to future configuration changes.

State Locking

helps to lock the state prevents multiples users to update the state file at a time.

* terraform download all plugins and store.terraform folder in the system 

Terraform starts with a single workspace named "default". This workspace is special both because it is the default and also because it cannot ever be deleted. If you've never explicitly used workspaces, then you've only ever worked on the "default" workspace.

what are default things created when created vpc ?

Important points to remember:

When you create a VPC, a default route table, Network Access Control List and default security group are automatically created.

It won't create any subnets, nor it will create a default internet gateway.

2. Can we run terraform file? where is it stored?

when we configured specific remote repo in a script it will generate the .tfstate in location, specified running the code. if not specifies automatically store in the local system.

the terraform generates state lock-in RDS used to lock from multiple users at a time to the resources until the code is applied successfully.

3. terraform init?

The terraform init command is used to initialize a working directory containing Terraform configuration files. This is the first command that should be run after writing a new Terraform configuration or cloning an existing one from version control. It is safe to run this command multiple times.

4. Jenkins installation and prerequisites?

Prerequisites

Minimum hardware requirements:

256 MB of RAM

1 GB of drive space (although 10 GB is a recommended minimum if running Jenkins as a Docker container)

Recommended hardware configuration for a small team:

4 GB+ of RAM

50 GB+ of drive space

Software requirements:

Java: see the Java Requirements page

Web browser: see the Web Browser Compatibility page

install jenkins based on the system https://www.jenkins.io/doc/book/installing/ and configure it .

5. how to hide passwords in Jenkins console output?

mask password plugin to hidden the password in Jenkins console output.

6.Jenkins configuration files stores in ?

Jenkins stores the configuration for each job within an eponymous directory in jobs/. The job configuration file is config.xml, the builds are stored in builds/, and the working directory is workspace/.

7. can I clone Jenkins jobs ? or can I move from one server to another?

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

How do I use Git ignore?

If you want to ignore a file that you've committed in the past, you'll need to delete the file from your repository and then add a . gitignore rule for it. Using the --cached option with git rm means that the file will be deleted from your repository, but will remain in your working directory as an ignored file.

what is upstream and downsteram jobs in jenkins ?

The upstream job is the one that is triggered before the actual job is triggered. The downstream job is the one that is triggered after the actual job is triggered. We can configure the actual job not to be triggered if the upstream job is failed. In the same way, we can configure the downstream job not to be triggered if the actual job is failed.

plugins : Buildflow plugin

steps :

1. create jobs required for setup flow
2. enter in to actual project (middle project)
3. go to build trigger section->build after  other (upstream )project build 
4. post build  select downstream project we can configure n number of projects 
5. apply and save 
6. in the dashboard you got the build pipeline view and name it then click ok
7. configure the necessary things  and select upstream project 
8. no of builds and give details 
9. apply and save it 
10. goto pipelines and click build 

VPC endpoints

A VPC endpoint enables private connections between your VPC and supported AWS services and VPC endpoint services powered by AWS PrivateLink. AWS PrivateLink is a technology that enables you to privately access services by using private IP addresses. Traffic between your VPC and the other service does not leave the Amazon network. A VPC endpoint does not require an internet gateway, virtual private gateway, NAT device, VPN connection, or AWS Direct Connect connection. Instances in your VPC do not require public IP addresses to communicate with resources in the service.

VPC endpoints are virtual devices. They are horizontally scaled, redundant, and highly available VPC components. They allow communication between instances in your VPC and services without imposing availability risks.

The following are the different types of VPC endpoints. You create the type of VPC endpoint that's required by the supported service.

Interface endpoints

An interface endpoint is an elastic network interface with a private IP address from the IP address range of your subnet. It serves as an entry point for traffic destined to a supported AWS service or a VPC endpoint service. Interface endpoints are powered by AWS PrivateLink.

For information about the AWS services that integrate with AWS PrivateLink, see AWS services that integrate with AWS PrivateLink. You can also view all of the available AWS service names. For more information, see View available AWS service names.

Gateway Load Balancer endpoints

A Gateway Load Balancer endpoint is an elastic network interface with a private IP address from the IP address range of your subnet. Gateway Load Balancer endpoints are powered by AWS PrivateLink. This type of endpoint serves as an entry point to intercept traffic and route it to a service that you've configured using Gateway Load Balancers, for example, for security inspection. You specify a Gateway Load Balancer endpoint as a target for a route in a route table. Gateway Load Balancer endpoints are supported for endpoint services that are configured for Gateway Load Balancers only.

Gateway endpoints

A gateway endpoint is for the following supported AWS services:

• Amazon S3

• DynamoDB

• 
  

How do I access S3 bucket from Amazon EC2 without access credentials?

You can access an S3 bucket privately without authentication when you access the S3 bucket from an Amazon Virtual Private Cloud (Amazon VPC) that has an endpoint to Amazon S3.

without credentials can i log in to server?

ssh-keygen creates the public and private keys. ssh-copy-id copies the local-host’s public key to the remote-host’s authorized_keys file. ssh-copy-id also assigns proper permission to the remote-host’s home, ~/.ssh, and ~/.ssh/authorized_keys.

.45 What are the types of jobs or projects in Jenkins?

• Freestyle project.
• Maven project.
• Pipeline.
• Multibranch pipeline.
• External Job.
• Multi-configuration project.
• Github organization.

What is a Shared Library in Jenkins?

A shared library is a collection of independent Groovy scripts which you pull into your Jenkinsfile at runtime.

The best part is, the Library can be stored, like everything else, in a Git repository. This means you can version, tag, and do all the cool stuff you’re used to with Git.

Not sure if you know Groovy? You’ve probably already it in Jenkins. It’s a Java-based scripting language, with a forgiving syntax.

Most things that you can do in Java, you can also do in Groovy. You don’t need to be a Groovy expert, but if you want to start fully learning Groovy, then you can find some learning resources here.

Here’s how you create a Jenkins library, step-by-step:

First you create your Groovy scripts (see further below for details), and add them into your Git repository.

Then, you add your Shared Library into Jenkins from the Manage Jenkins screen.

Finally, you pull the Shared Library into your pipeline using this annotation (usually at the top of your Jenkinsfile):

@Library('your-library-name')

Docker Components? 

What is mean by ansible vault

Credentials where you stored in ansible

Facts in ansible

What is mean by ansible roles

Difference between docker compose and docker swarm

Difference between docker swarm and kubernetes

difference between EBS vs EFS vs S3

how to launch static website using s3 ?

How you will give access to specific user from specific bucket ?

s3 life cycle policy

what is mean by versioning in s3

How you do cross region replication on s3

Difference between IAM Policies and IAM Roles

IAM policy structure ?

What is mean by inline policy on IAM

What is the use of IAM roles ?

What is mean by Jenkins library