The terraform apply command is a fundamental component of the Core Terraform Workflow and represents the execution phase where infrastructure changes are actually implemented. This command takes the execution plan generated by terraform plan and applies those changes to reach the desired state defi…The terraform apply command is a fundamental component of the Core Terraform Workflow and represents the execution phase where infrastructure changes are actually implemented. This command takes the execution plan generated by terraform plan and applies those changes to reach the desired state defined in your configuration files.
When you run terraform apply, Terraform first performs a refresh operation to update the state file with the current status of existing resources. It then calculates what changes need to be made by comparing the desired configuration against the current state. Before making any modifications, Terraform displays a detailed execution plan showing all proposed additions, modifications, and deletions.
By default, terraform apply requires interactive approval before proceeding with changes. You must type 'yes' to confirm the operations. This safety mechanism prevents accidental infrastructure modifications. For automation scenarios, you can use the -auto-approve flag to skip this confirmation prompt.
The command supports several useful options. You can pass a saved plan file from a previous terraform plan execution using terraform apply planfile. The -var and -var-file flags allow you to specify input variables. The -target flag enables you to apply changes to specific resources only.
During execution, Terraform creates, updates, or destroys resources in the correct order based on dependency relationships. It handles parallelization automatically where possible to optimize performance. Progress is displayed in real-time, showing which resources are being modified.
Upon successful completion, Terraform updates the state file to reflect the new infrastructure configuration. If errors occur during application, Terraform attempts to complete as many operations as possible and reports failures clearly. The state file accurately reflects the actual infrastructure state, even when partial failures occur.
Understanding terraform apply is essential for the Terraform Associate certification as it represents the critical step where infrastructure changes transition from planned to realized.
The Terraform Apply Command - Complete Guide
What is the Terraform Apply Command?
The terraform apply command is the execution phase of the core Terraform workflow. It takes the planned changes and implements them against your infrastructure, creating, modifying, or destroying resources as specified in your configuration files.
Why is Terraform Apply Important?
The apply command is crucial because it is the step where actual infrastructure changes occur. Understanding this command is essential for:
• Infrastructure Deployment: It creates real resources in your cloud environment • Change Management: It modifies existing infrastructure to match your desired state • State Management: It updates the Terraform state file to reflect current infrastructure • Automation: It enables CI/CD pipelines to deploy infrastructure programmatically
How Terraform Apply Works
1. Plan Generation: By default, terraform apply first runs a plan to show proposed changes 2. User Confirmation: Terraform prompts for approval before making changes (unless using -auto-approve) 3. Resource Operations: Terraform executes create, update, or destroy operations in the correct order based on dependencies 4. State Update: The state file is updated to reflect the new infrastructure state 5. Output Display: Any defined outputs are displayed upon completion
Key Flags and Options:
• -auto-approve: Skips the interactive approval step • -var: Sets input variables from the command line • -var-file: Specifies a file containing variable values • -target: Limits the apply to specific resources • -parallelism: Controls the number of concurrent operations • -input=false: Disables interactive prompts
Using a Saved Plan File:
You can separate planning and applying by using: terraform plan -out=tfplan followed by terraform apply tfplan. When applying a saved plan, Terraform skips the confirmation prompt because the plan was already reviewed.
Exam Tips: Answering Questions on The Terraform Apply Command
• Remember the Default Behavior: Terraform apply generates a plan and asks for confirmation before proceeding. Know that -auto-approve bypasses this confirmation.
• Understand Plan Files: When a saved plan file is provided to terraform apply, no confirmation is required because the plan was pre-approved when saved.
• Know the Order: The core workflow order is init → plan → apply. Questions may test whether you understand this sequence.
• State File Updates: Remember that terraform apply updates the state file after successful resource operations.
• Target Flag Usage: The -target flag should be used cautiously and is primarily for exceptional situations, not regular workflows.
• Exit Codes: Terraform apply returns exit code 0 on success and 1 on error. This is important for automation scenarios.
• Partial Applies: If an apply fails partway through, already-created resources remain, and the state reflects what was successfully created.
• Refresh Behavior: By default, terraform apply refreshes the state before planning. You can use -refresh=false to skip this.
Common Exam Question Patterns:
• What happens when you run terraform apply with a saved plan file? • Which flag skips the approval prompt during terraform apply? • What is the correct sequence of Terraform commands for deploying infrastructure? • How does terraform apply handle resource dependencies?