Navigate Terraform workflow

Question 1

What is the Core Terraform workflow?

Answer 1

The core Terraform workflow has three steps:

1. Write - Author infrastructure as code.
2. Plan - Preview changes before applying.
3. Apply - Provision reproducible infrastructure.

Question 2

What is the workflow when you work as an Individual Practitioner?

Answer 2

https://www.terraform.io/guides/core-workflow.html#working-as-an-individual-practitioner

Question 3

What is the workflow when you work as a team?

Answer 3

https://www.terraform.io/guides/core-workflow.html#working-as-a-team

Question 4

What is the workflow when you work as a large organization?

Answer 4

https://www.terraform.io/guides/core-workflow.html#the-core-workflow-
enhanced-by-terraform-cloud

Question 5

What is the command init?

Answer 5

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.

Question 6

You recently joined a team and you cloned a terraform configuration files from
the version control system. What is the first command you should use?

Answer 6

terraform init
This command performs several different initialization steps in order
to prepare a working directory for use.
This command is always safe to run multiple times, to bring the
working directory up to date with changes in the configuration.Though subsequent runs may give errors, this command will never
delete your existing configuration or state.
If no arguments are given, the configuration in the current working
directory is initialized. It is recommended to run Terraform with the
current working directory set to the root directory of the
configuration, and omit the DIR argument.
https://www.terraform.io/docs/commands/init.html

Question 7

What is the flag you should use to upgrade modules and plugins a part of their
respective installation steps?

Answer 7

upgrade

terraform init -upgrade

Question 8

When you are doing initialization with terraform init, you want to skip backend
initialization. What should you do?

Answer 8

terraform init -backend=false

Question 9

When you are doing initialization with terraform init, you want to skip child
module installation. What should you do?

Answer 9

terraform init -get=false

Question 10

When you are doing initialization where do all the plugins stored?

Answer 10

On most operationg systems
~/.terraform.d/plugins

on Windows
%APPDATA%\terraform.d\plugins

Question 11

When you are doing initialization with terraform init, you want to skip plugin
installation. What should you do?

Answer 11

terraform init -get-plugins=false
Skips plugin installation. Terraform will use plugins installed in
the user plugins directory, and any plugins already installed for the
current working directory. If the installed plugins aren’t sufficient
for the configuration, init fails.

Question 12

What does the command terraform validate does?

Answer 12

The terraform validate command validates the configuration files in a
directory, referring only to the configuration and not accessing any
remote services such as remote state, provider APIs, etc.
Validate runs checks that verify whether a configuration is
syntactically valid and internally consistent, regardless of any
provided variables or existing state.
It is thus primarily useful for general verification of reusable
modules, including correctness of attribute names and value types.
https://www.terraform.io/docs/commands/validate.html

Question 13

What does the command plan do?

Answer 13

The terraform plan command is used to create an execution plan.
Terraform performs a refresh, unless explicitly disabled, and then
determines what actions are necessary to achieve the desired state
specified in the configuration files.

Question 14

What does the command apply do?

Answer 14

The terraform apply command is used to apply the changes required to
reach the desired state of the configuration, or the pre-determined
set of actions generated by a terraform plan execution plan.

Question 15

You are applying the infrastructure with the command apply and you don’t want
to do interactive approval. Which flag should you use?

Answer 15

terraform apply -auto-approve

https://www.terraform.io/docs/commands/apply.html

Question 16

What does the command destroy do?

Answer 16

The terraform destroy command is used to destroy the Terraform-managed infrastructure.

Question 17

How do you preview the behavior of the command terraform destroy?

Answer 17

terraform plan -destroy

Question 18

What are implicit and explicit dependencies?

Answer 18

Implicit dependency:
By studying the resource attributes used in interpolation expressions, Terraform can automatically infer when one resource depends on another.
Terraform uses this dependency information to determine the correct order in which to create the different resources.
Implicit dependencies via interpolation expressions are the primary way to inform Terraform about these relationships, and should be used whenever possible.

Explicit dependency:
Sometimes there are dependencies between resources that are not visible to Terraform. The depends_on argument is accepted by any resource and accepts a list of resources to create explicit
dependencies for.

Question 19

Give an example of implicit dependency?

Answer 19

In the example below, the reference to aws_instance.example.id
creates an implicit dependency on the aws_instance named example.
provider "aws" {
profile = "default"
region = "us-east-1"
}
resource "aws_instance" "example" {
ami = "ami-b374d5a5"
instance_type = "t2.micro"
}
resource "aws_eip" "ip" {
vpc = true
instance = aws_instance.example.id
}

Question 20

Give an example of explicit dependency?

Answer 20

In the example below, an application we will run on our EC2 instance
expects to use a specific Amazon S3 bucket, but that dependency is
configured inside the application code and thus not visible to
Terraform. In that case, we can use depends_on to explicitly declare the dependency

resource "aws_s3_bucket" "example" {
bucket = "some_bucket"
acl = "private"
}
resource "aws_instance" "example" {
ami = "ami-2757f631"
instance_type = "t2.micro"
}
depends_on = [aws_s3_bucket.example]
}

Question 21

How do you save the execution plan?

Answer 21

terraform plan -out=tfplan
you can use that file with apply
terraform apply tfplan

Question 22

You have started writing terraform configuration and you are using some sample
configuration as a basis. How do you copy the example configuration into your
working directory?

Answer 22

terraform init -from-module=MODULE-SOURCE

https://www.terraform.io/docs/commands/init.html#copy-a-source-module

Question 23

What is the flag you should use with the terraform plan to get detailed on the exit codes?

Answer 23

terraform plan -detailed-exitcode
Return a detailed exit code when the command exits. When provided,
this argument changes the exit codes and their meanings to provide
more granular information about what the resulting plan contains:
* 0 = Succeeded with empty diff (no changes)
* 1 = Error
* 2 = Succeeded with non-empty diff (changes present)

Question 24

How do you target only specific resources when you run a terraform plan?

Answer 24

-target=resource - A Resource Address to target. This flag can be used multiple times. See below for more information.

Question 25

How do you update the state prior to checking differences when you run a
terraform plan?

Answer 25

terraform plan -refresh=true

Question 26

The behavior of any terraform destroy command can be previewed at any time
with an equivalent terraform plan -destroy command. Is this true?

Answer 26

True

Question 27

You have the following file and created two resources docker_image and
docker_container with the command terraform apply and you go to the terminal and
delete the container with the command docker rm. You come back to your
configuration and run the command again. Does terraform recreates the resource?

Answer 27

Yes. Terraform creates the resource again since the execution plan says two resources and the terraform always maintains the desired state

Question 28

You created a VM instance on AWS cloud provider with the terraform
configuration and you log in AWS console and removed the instance. What does the
next apply do?

Answer 28

It creates the instance again

Question 29

You have the following file and created two resources docker_image and
docker_container with the command terraform plan and you go to the terminal and
delete the container with the command docker rm. You come back to your
configuration and run the command again. What is the output of the command plan?

Answer 29

Terraform will perform the following actions:
# docker_container.nginx will be created
Plan: 1 to add, 0 to change, 0 to destroy.