Terraform terminologies.

Let’s start Terraform, and understand some key terminologies and concepts. Here are some fundamental terms and explanations.

1. Provider: A provider is a plugin for Terraform that defines and manages resources for a specific cloud or infrastructure platform. Examples of providers include AWS, Azure, Google Cloud, and many others. You configure providers in your Terraform code to interact with the desired infrastructure platform.
2. Resource: A resource is a specific infrastructure component that you want to create and manage using Terraform. Resources can include virtual machines, databases, storage buckets, network components, and more. Each resource has a type and configuration parameters that you define in your Terraform code.
3. Module: A module is a reusable and encapsulated unit of Terraform code. Modules allow you to package infrastructure configurations, making it easier to maintain, share, and reuse them across different parts of your infrastructure. Modules can be your own creations or come from the Terraform Registry, which hosts community-contributed modules.
4. Configuration File: Terraform uses configuration files (often with a .tf extension) to define the desired infrastructure state. These files specify providers, resources, variables, and other settings. The primary configuration file is usually named main.tf, but you can use multiple configuration files as well.
5. Variable: Variables in Terraform are placeholders for values that can be passed into your configurations. They make your code more flexible and reusable by allowing you to define values outside of your code and pass them in when you apply the Terraform configuration.
6. Output: Outputs are values generated by Terraform after the infrastructure has been created or updated. Outputs are typically used to display information or provide values to other parts of your infrastructure stack.
7. State File: Terraform maintains a state file (often named terraform.tfstate) that keeps track of the current state of your infrastructure. This file is crucial for Terraform to understand what resources have been created and what changes need to be made during updates.
8. Plan: A Terraform plan is a preview of changes that Terraform will make to your infrastructure. When you run terraform plan, Terraform analyzes your configuration and current state, then generates a plan detailing what actions it will take during the apply step.
9. Apply: The terraform apply command is used to execute the changes specified in the plan. It creates, updates, or destroys resources based on the Terraform configuration.
10. Workspace: Workspaces in Terraform are a way to manage multiple environments (e.g., development, staging, production) with separate configurations and state files. Workspaces help keep infrastructure configurations isolated and organized.
11. Remote Backend: A remote backend is a storage location for your Terraform state files that is not stored locally. Popular choices for remote backends include Amazon S3, Azure Blob Storage, or HashiCorp Terraform Cloud. Remote backends enhance collaboration and provide better security and reliability for your state files.

These are some of the essential terms you’ll encounter when working with Terraform. As you start using Terraform for your infrastructure provisioning and management, you’ll become more familiar with these concepts and how they fit together in your IaC workflows.

Why Terraform ?

There are multiple reasons why Terraform is used over the other IaC tools but below are the main reasons.

1. Multi-Cloud Support: Terraform is known for its multi-cloud support. It allows you to define infrastructure in a cloud-agnostic way, meaning you can use the same configuration code to provision resources on various cloud providers (AWS, Azure, Google Cloud, etc.) and even on-premises infrastructure. This flexibility can be beneficial if your organization uses multiple cloud providers or plans to migrate between them.
2. Large Ecosystem: Terraform has a vast ecosystem of providers and modules contributed by both HashiCorp (the company behind Terraform) and the community. This means you can find pre-built modules and configurations for a wide range of services and infrastructure components, saving you time and effort in writing custom configurations.
3. Declarative Syntax: Terraform uses a declarative syntax, allowing you to specify the desired end-state of your infrastructure. This makes it easier to understand and maintain your code compared to imperative scripting languages.
4. State Management: Terraform maintains a state file that tracks the current state of your infrastructure. This state file helps Terraform understand the differences between the desired and actual states of your infrastructure, enabling it to make informed decisions when you apply changes.
5. Plan and Apply: Terraform’s “plan” and “apply” workflow allows you to preview changes before applying them. This helps prevent unexpected modifications to your infrastructure and provides an opportunity to review and approve changes before they are implemented.
6. Community Support: Terraform has a large and active user community, which means you can find answers to common questions, troubleshooting tips, and a wealth of documentation and tutorials online.
7. Integration with Other Tools: Terraform can be integrated with other DevOps and automation tools, such as Docker, Kubernetes, Ansible, and Jenkins, allowing you to create comprehensive automation pipelines.
8. HCL Language: Terraform uses HashiCorp Configuration Language (HCL), which is designed specifically for defining infrastructure. It’s human-readable and expressive, making it easier for both developers and operators to work with.

Using workspace you can provision more than one environments. To do this using workspaces, you first create a workspace called dev using the terraform workspace new command:

$ terraform workspace new prod

terraform workspace new prod

terraform apply

… output trimmed..

As you can see new workspace ‘prod’ is created and new infrastructure is provisioned.

Note: * prod (* is showing current workspace).

terraform workspace select default

Now there are 6 instances up and running…

Question: How to change the server names and tags in PROD?

All commands will be applicable to current worspace.

After destroying prod, still you will be there. If you want to work in another env, change to it.

count

The count parameter in Terraform allows you to create a specified number of identical resources. It is an integral part of a resource block that defines how many instances of a particular resource should be created.

Pros:

• Simple to use: The count parameter is straightforward for creating multiple instances of a resource.
• Suitable for homogeneous resources: When all the resources you’re creating are identical except for an identifier, count is likely a good fit.

Cons:

• Lacks key-based identification: count doesn’t include a way to address a resource with a unique key directly; you have to rely on an index.
• Immutable: If you remove an item from the middle of the count list, Terraform marks all subsequent resources for recreation which can be disruptive in certain scenarios.

count = 3 is added.

One EC2 had already been created, therefore it added 2 more. This feature is called… ” “.

Screenshot from aws console.

for_each

The for_each loop in Terraform, used within the for_each argument, iterates over a map or a set of strings, allowing you to create resources that correspond to the given elements.

Pros:

• Detailed declaration: for_each provides greater control when creating resources that require specific attributes or configurations.
• Key-based identification: Resources created with for_each can be directly identified and accessed by their keys, making modifications more manageable.
• Non-destructive updates: If you remove an item from the map or set, only that specific resource will be affected.

Cons:

• Complexity: for_each is more complex to use than count and requires more planning.
• Requires a set or map: You must provide a set or map of items to iterate over, which might not be necessary or straightforward for all situations.

When to Use Count vs. For_each

Both constructs are powerful, but they shine in different situations. Here’s a quick reference to determine which to use:

Use Count when:

• You need to create a fixed number of similar resources.
• Resource differences can be represented by an index.

Use For_each when:

• You’re dealing with a collection of items that have unique identifiers.
• Your resources are not perfectly identical and require individual configurations.
• You plan to make future modifications that should not affect all resources.

Terraform script (main.tf) to create the vpc in aws.

1. terraform init
2. terraform validate
3. terraform plan -out sanjayShonak_vpc
4. terraform apply “sanjayShonak_VPC”

terraform plan -out sanjayShonak_vpc

… output trimmed…

Note: it’s best practice to provide output file. In that case you can use the command provided at the end.

terraform apply “sanjayShonak_VPC”

… output trimmed. As you can see it has added 16 resources.

terraform state

This does advanced state management. The 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.

Option	Description
list	List resources in the state.
show	Show a resource in the state.
mv	Move an item in the state.
rm	Remove instances from the state.
pull	Pull current state and output to stdout.

terraform state list

terraform state show aws_route_table_association.rta1

terraform state show aws_lb.myalb

… output trimmed.

terraform graph

Produces a representation of the dependency graph between different objects in the current configuration and state. The graph is presented in the DOT language. The typical program that can read this format is GraphViz, but many web services are also available to read this format.

terraform graph

terraform destroy