Terraform CLI Commands

The Terraform CLI is the primary interface for working with infrastructure code. Understanding each command’s purpose, key flags, and when to use them is essential for both day-to-day work and DevOps interviews.

Core Workflow Commands

`terraform init`

Initializes the working directory — downloads providers, sets up the backend, and prepares modules.

terraform init                         # Standard initialization
terraform init -upgrade                # Upgrade providers within constraints
terraform init -backend=false          # Skip backend configuration (local testing)
terraform init -reconfigure            # Force backend reconfiguration
terraform init -backend-config="bucket=my-state-bucket"  # Override backend settings

Run init whenever:

Starting a new project
Adding/changing providers
Changing backend configuration
After cloning a repo

`terraform validate`

Checks syntax and internal consistency without accessing any remote APIs.

terraform validate                     # Validate current directory
terraform validate -json               # Machine-readable JSON output (for CI)

validate catches: missing required arguments, type mismatches, invalid references. It does NOT catch: API-side errors (wrong AMI ID, insufficient permissions).

`terraform fmt`

Automatically formats .tf files to canonical HCL style.

terraform fmt                          # Format current directory
terraform fmt -recursive               # Format all subdirectories too
terraform fmt -check                   # Exit 1 if files need formatting (use in CI)
terraform fmt -diff                    # Show diff of changes

Add terraform fmt -check -recursive to your CI pipeline to enforce consistent formatting.

`terraform plan`

Creates an execution plan showing what changes will be made.

terraform plan                         # Basic plan
terraform plan -out=tfplan             # Save plan to file (use with apply)
terraform plan -var="environment=prod" # Override a variable
terraform plan -var-file="prod.tfvars" # Use a specific vars file
terraform plan -target=aws_instance.web # Plan only specific resource
terraform plan -destroy                # Show what destroy would remove
terraform plan -refresh=false          # Skip state refresh (faster, less safe)
terraform plan -compact-warnings       # Summarize warnings

The output symbols:

+ Resource will be created
- Resource will be destroyed
~ Resource will be updated in-place
-/+ Resource will be destroyed and recreated

`terraform apply`

Applies changes to reach the desired state.

terraform apply                        # Show plan, prompt for confirmation
terraform apply -auto-approve          # Skip confirmation (use in CI/CD only)
terraform apply tfplan                 # Apply a saved plan file (no re-plan)
terraform apply -var="env=prod"        # Override variable
terraform apply -target=aws_s3_bucket.logs  # Apply only one resource
terraform apply -parallelism=20        # Concurrent operations (default: 10)

Best practice for production: terraform plan -out=tfplan && terraform apply tfplan. This guarantees what you reviewed is exactly what gets applied.

`terraform destroy`

Destroys all resources managed by the configuration.

terraform destroy                      # Prompt for confirmation
terraform destroy -auto-approve        # No confirmation (use with extreme care)
terraform destroy -target=aws_instance.old  # Destroy a specific resource only

State Management Commands

`terraform show`

Displays current state or a saved plan.

terraform show                         # Show current state
terraform show tfplan                  # Show saved plan contents
terraform show -json | jq '.values'   # Parse state as JSON

`terraform state`

Directly inspect and manipulate the state file.

terraform state list                          # List all managed resources
terraform state show aws_instance.web         # Details of one resource
terraform state mv aws_instance.old aws_instance.new  # Rename resource in state
terraform state rm aws_instance.web           # Remove from state (doesn't delete real resource)
terraform state pull                          # Download remote state to stdout
terraform state push terraform.tfstate        # Upload local state to backend

`terraform import`

Import existing infrastructure into Terraform state.

terraform import aws_s3_bucket.existing my-existing-bucket
terraform import aws_instance.server i-1234567890abcdef0

Utility Commands

`terraform output`

Read outputs after apply.

terraform output                       # All outputs
terraform output vpc_id                # Specific output
terraform output -json                 # JSON format (for scripting)
terraform output -raw load_balancer_dns  # Raw string (no quotes)

`terraform console`

Interactive REPL for evaluating expressions.

terraform console
> cidrsubnet("10.0.0.0/16", 8, 1)
"10.0.1.0/24"
> length(["a", "b", "c"])
3
> var.environment
"production"

`terraform workspace`

Manage named workspaces for state isolation.

terraform workspace list               # List workspaces
terraform workspace new staging        # Create and switch to staging
terraform workspace select production  # Switch workspace
terraform workspace show               # Current workspace name
terraform workspace delete staging     # Delete a workspace

`terraform graph`

Outputs the dependency graph in DOT format.

terraform graph | dot -Tsvg > graph.svg  # Visualize with Graphviz

Frequently Used Flags Cheat Sheet

Flag	Commands	Purpose
`-auto-approve`	apply, destroy	Skip interactive confirmation
`-var="key=val"`	plan, apply	Override a single variable
`-var-file=file`	plan, apply	Load variables from file
`-target=resource`	plan, apply, destroy	Limit to specific resource
`-out=file`	plan	Save plan for later apply
`-refresh=false`	plan, apply	Skip state refresh
`-lock=false`	plan, apply	Disable state locking (caution)
`-compact-warnings`	plan, apply	Suppress verbose warnings
`-json`	plan, apply, show	JSON output for tooling

CI/CD-Friendly Workflow

# In CI pipelines — non-interactive, explicit, auditable
terraform init -input=false
terraform validate
terraform fmt -check -recursive
terraform plan -out=tfplan -input=false
terraform apply -input=false tfplan

The -input=false flag causes Terraform to fail rather than prompt for user input, which is the correct behavior in automated pipelines.