DevOps - Terraform Question

Question 1

Q1: What are terraform state files

Answer 1

Terraform state file stores the meta data about the infrastructure. By default, they are store local in the folder where the terraform code is. But you can configure to store in public cloud using backend.

Question 2

What difference between terraform.tfvars and variable.tf

Answer 2

Avariables.tffile is used to define thevariables typeand optionallyset a default value.

Aterraform.tfvarsfile is used toset the actual valuesof the variables. tfvars are general use for different environment like prod.tfvars, dev.tfvars

https: //cloudbuild.co.uk/tag/tfvars-vs-variables-tf
https: //stackoverflow.com/questions/56086286/terraform-tfvars-vs-variables-tf-difference

Question 3

How can you assign variable to terraform code?

Answer 3

There are several different ways to assign avalueto this input variable:

• Includevaroptions on theterraform planorterraform applycommand line.
• Includevar-fileoptions to select one or more.tfvarsfiles to set values for many variables at once.
• Create aterraform.tfvarsfile, or files named.auto.tfvars, which are treated the same asvar-filearguments but are loaded automatically.
• For a child module, include an expression to assign to the variable inside the callingmoduleblock.

https://www.notion.so/Terraform-8628f7defe754354a8114a0cf32f9267#738ebb2b8ffb4c279781c2c4b7b93f65

Question 4

What are taint in terraform

Answer 4

Theterraform taint command informs Terraform that a particular object has become degraded or damaged. Terraform represents this by marking the object as “tainted” in the Terraform state, and Terraform will propose to replace it in the next plan you create.

Question 5

What are null resource in terraform

Answer 5

Thenull_resourceresource implements the standard resource lifecycle but takes no further action.

As the null_resource doesn’t actually manage any underlying item without the triggers once it was created nothing would ever change again. The triggers parameter allows the resource to respond to changes, causing the resource to be destroyed & recreated, impacting on any dependencies or attached provisions.

https://www.notion.so/Terraform-8628f7defe754354a8114a0cf32f9267#43903092485b430fa41ca8871274dfcd

Question 6

What are triggers in terraform

Answer 6

Thetriggersargument allows specifying an arbitrary set of values that, when changed, will cause the resource to be replaced.

Question 7

What are data source in terraform

Answer 7

Data sources allow Terraform to use information defined outside of Terraform.

Yes, you can use data sources in Terraform to query resources that were not created by Terraform itself. Data sources allow you to fetch information about existing resources in your infrastructure, regardless of whether they were provisioned by Terraform or another tool.

Here, in this example, existing vpc cidr block is use to create subnet

variable "vpc_id" {}

data "aws_vpc" "selected" {
  id = var.vpc_id
}

resource "aws_subnet" "example" {
  vpc_id            = data.aws_vpc.selected.id
  availability_zone = "us-west-2a"
  cidr_block        = cidrsubnet(data.aws_vpc.selected.cidr_block, 4, 1)
}

Question 8

What is dynamic block in terrafrom?

Answer 8

You can dynamically construct repeatable nested blocks likesettingusing a specialdynamicblock type, which is supported insideresource,data,provider, andprovisionerblocks

resource “aws_elastic_beanstalk_environment” “tfenvtest” {
name = “tf-test-name”
application = “${aws_elastic_beanstalk_application.tftest.name}”
solution_stack_name = “64bit Amazon Linux 2018.03 v2.11.4 running Go 1.12.6”

  dynamic "setting" {
    for_each = var.settings
    content {
      namespace = setting.value["namespace"]
      name = setting.value["name"]
      value = setting.value["value"]
    }
  }
}

Question 9

What are Multi-level Nested Block Structures?

Answer 9

nesteddynamicblocks:

dynamic “origin_group” {
for_each = var.load_balancer_origin_groups
content {
name = origin_group.key

      dynamic "origin" {
        for_each = origin_group.value.origins
        content {
          hostname = origin.value.hostname
        }
      }
    }
  }

Question 10

What are provisioners in the Terraform? What there use?

Answer 10

Provisioners can be used to model specific actions on the local machine or on a remote machine in order to prepare servers or other infrastructure objects for service.

Examples are

• local-exec = execute command on local machine where code is run
• remote-exec = provisioner invokes a script on a remote resource after it is created
• File Provisioner = copies files or directories from the machine running Terraform to the newly created resource.

Question 11

Q11: What are plugins and providers in terraform?

Answer 11

Terraform Plugins: These are executable binaries written in Go that communicate with Terraform Core over an RPC interface. Each plugin exposes an implementation for a specific service, such as theAWS provideror thecloud-init provider. Terraform currently supports one type of Plugin calledproviders.

Question 12

How do you lock the terraform statefile?

Answer 12

If supported by yourbackend, Terraform will lock your state for all operations that could write state. This prevents others from acquiring the lock and potentially corrupting your state.

If backend is S3, lock needs dynamoDB table for locking

Question 13

Few challenges that you came across while working with terraform?

Answer 13

• Manual changes needs to be sync
• Changing resource name after creation as name depended on resource use name with suffix. e.g ec2 tag name, security-group, user-data files, etc.
• Importing existing resource
• Different version of terraform state file

Question 14

How to call the existing resource from AWS or Azure to terraform without hardcoding the values or terraform import?

Answer 14

Use Data type, you can use manual resource