Terraform Configuration Files and Overrides Quiz

Terraform Fundamentals

• Terraform configuration files are often called configuration files.
• Terraform loads all files ending in .tf in a directory.

Terraform Plan

• terraform plan -out filename generates a plan file, which is a zip file.
• The plan file can be used when applying: terraform apply "nat.tfplan".

Terraform Validate

• terraform validate validates the syntax.

Terraform Plan Options

• terraform plan [-destroy] generates an execution plan for Terraform.

Provider Configuration

• The profile attribute refers to the AWS Config File in ~/.aws/credentials on MacOS and Linux or %UserProfile%\.aws\credentials on a Windows system.
• It is recommended not to hardcode credentials into .tf configuration files.
• The provider "aws" block defines the default AWS config profile and region.

Resource Blocks

• A resource block has two strings before opening the block: the resource type and the resource name.
• Each "Provider" is its own encapsulated binary distributed separately from Terraform itself.
• The terraform init command will automatically download and install any Provider binary for the providers in use within the configuration.

Terraform State

• Terraform writes data into the terraform.tfstate file, which keeps track of the IDs of created resources.
• This state file is extremely important and must be saved and distributed to anyone who might run Terraform.
• terraform show can be used to inspect the current state.

Resource Dependencies

• Implicit dependencies via interpolation expressions are the primary way to inform Terraform about relationships.
• The depends_on argument is accepted by any resource and accepts a list of resources to create explicit dependencies.

Override Files

• Terraform has special handling of any configuration file whose name ends in _override.tf or _override.tf.json.
• Override files are processed in lexicographical order after the initial configuration file.
• Use override files only in special circumstances, as over-use hurts readability.

Variable Definitions

• Terraform searches the environment of its own process for environment variables named TF_VAR_ followed by the name of a declared variable.
• Terraform automatically loads .tfvars or *.auto.tfvars files present in the current directory to populate variables.
• A .tfvars file is used to assign values to variables, not to declare new variables.