Installing Terraform and the CLI Workflow

Overview

Install Terraform 1.x, pin a version with tfenv or asdf, verify the binary, and understand how providers arrive from the Terraform Registry on init.

Install via package manager, HashiCorp packages, or a version manager. Pin the CLI version for every root module with required_version. Providers download from the Terraform Registry on first terraform init — not at install time.

This is a core tutorial in Module 2 · Installing Terraform of the REBASH Academy Terraform for Cloud & DevOps Engineers series — written for Cloud, DevOps, Platform, and SRE engineers.

Prerequisites

• Introduction to Terraform and IaC
• Network access to download the CLI and (later) providers

Learning Objectives

By the end of this tutorial, you will be able to:

• Install and verify terraform version
• Pin versions with tfenv or asdf
• Explain when providers download (init + Registry)
• List core CLI verbs you will use daily

Architecture

This topic’s control points and relationships are shown below.

Theory

What it is

Installing Terraform means putting the Terraform CLI on your workstation or CI image. The binary alone does not ship cloud plugins; providers are separate plugins resolved from the Terraform Registry (or a private mirror) when you run terraform init in a configuration that declares required_providers.

Version managers such as tfenv or asdf (with a Terraform plugin) let you switch CLI versions per project — essential when repos pin different required_version constraints.

Action	Purpose
terraform version	Confirm CLI (and later, provider versions after init)
terraform init	Download providers/modules; prepare backend
terraform fmt / validate	Format and syntax-check
terraform plan / apply	Preview and execute changes

Why it matters

Production teams pin Terraform and provider versions so plans are reproducible across laptops and pipelines. A floating “latest” binary on one engineer’s machine and an older image in CI is a classic source of “works locally” plan diffs. Enterprises often mirror the Registry or use HCP Terraform / private registries so CI does not pull unapproved plugins.

How it works

1. Install Terraform 1.x via Homebrew, Linux packages from HashiCorp, a direct zip, or tfenv / asdf.
2. Verify with terraform version (expect 1.x).
3. Optionally set a .terraform-version (tfenv) or .tool-versions (asdf) in the repo.
4. Declare required_version and required_providers in a terraform block.
5. On terraform init, the CLI reads those constraints, downloads matching provider plugins into .terraform/, and writes a lock file (.terraform.lock.hcl).

You do not install AWS or Azure providers with a separate package manager for day-to-day use — init does that from the Registry.

Key concepts and comparisons

Method	Fit
Package manager (brew, apt repo)	Quick local install
tfenv / asdf	Multi-version teams and CI parity
Official zip / container image	Locked CI images and air-gapped builds
Registry on init	Provider and module distribution

Common pitfalls

• Installing Terraform once and never pinning — plans diverge across machines.
• Expecting providers to appear after CLI install without a configuration and init.
• Mixing Terraform 0.11/0.12 habits with modern 1.x workflows.
• Committing .terraform/ (plugins cache) — commit .terraform.lock.hcl, not the plugin directory.
• Using a personal laptop binary for production applies — prefer CI with a pinned image.

Hands-on Lab

Create a workspace for this tutorial.

mkdir -p ~/rebash-terraform/module-02 && cd ~/rebash-terraform/module-02

Focus: Practise the core CLI workflow: init, validate, plan, apply, destroy

Step 1 – Initialise and validate

cat > main.tf <<'EOF'
terraform {
  required_version = ">= 1.5.0"
  required_providers {
    null = {
      source  = "hashicorp/null"
      version = "~> 3.2"
    }
    local = {
      source  = "hashicorp/local"
      version = "~> 2.5"
    }
  }
}

resource "null_resource" "lab" {
  triggers = {
    note = "rebash-lab"
  }
}

resource "local_file" "marker" {
  content  = "managed-by-terraform
"
  filename = "${path.module}/marker.txt"
}
EOF
terraform version
terraform init
terraform validate
terraform fmt -check || terraform fmt

Step 2 – Plan, apply, then prove destroy works

terraform plan -out=tfplan
terraform apply tfplan
ls -la marker.txt
terraform destroy -auto-approve
test ! -f marker.txt && echo "destroyed OK"
# Recreate for the cleanup step below
terraform apply -auto-approve

Final step – Cleanup note

terraform destroy -auto-approve
# Workspace kept for notes; remove with: rm -rf "$(pwd)" when finished

Validation

• Lab commands run under ~/rebash-terraform/module-02/
• You can explain each Theory section in your own words
• You used modern tooling where it applies to this topic
• You can describe one production failure mode for this topic

Code Walkthrough

Production practice for Installing Terraform and the CLI Workflow always combines:

1. Inspect before you change (status, plan, logs, dry-run)
2. Prefer reversible, documented changes (Git, IaC, drop-ins, version pins)
3. Capture evidence (command output, pipeline logs) for handovers
4. Prefer current tools and APIs over legacy shortcuts
5. Least privilege — escalate credentials only when required

Keep runbooks short enough to follow under pressure. Automate checks; keep humans for judgement.

Security Considerations

• Treat credentials and tokens for terraform as privileged — never commit them
• Prefer short-lived auth (OIDC, roles, SSO) over long-lived keys
• Validate blast radius before apply/deploy/delete operations
• Restrict who can approve production changes
• Collect audit logs; limit who can read sensitive traces

Common Mistakes

Installing Terraform once and never pinning — plans diverge across machines.

Validate assumptions against the Theory section and official docs before changing production.

Expecting providers to appear after CLI install without a configuration and init.

Lab shortcuts (open security groups, admin roles, skip approvals) must not ship unchanged.

Changing production without a rollback path

Always know how to revert (previous artefact, prior release, state rollback, DNS failback).

Best Practices

• Encode Installing Terraform and the CLI Workflow changes as code and review them in pull requests
• Pin versions (images, modules, actions, provider plugins)
• Separate environments with clear promotion gates
• Alert on symptoms with runbooks attached
• Destroy lab resources; tag everything with owner and expiry where possible

Troubleshooting

Symptom	Likely cause	Fix
Auth / permission denied	Wrong identity, policy, or scope	Check caller identity, roles, and least-privilege policies
Timeout / no route	Network, DNS, security group, or endpoint	Trace path, DNS, and allow-lists before retrying
Drift / unexpected plan	Manual change or wrong state/workspace	Reconcile desired vs actual; avoid click-ops on managed resources
Pipeline/job red	Flaky step, cache, or missing secret	Read failing step logs; bisect recent workflow/config changes
Cost spike	Idle load balancer, NAT, oversized compute	Inventory billable resources; stop/delete labs promptly

Summary

Installing Terraform and the CLI Workflow is essential for Cloud and DevOps engineers working with terraform. Practise the lab until the inspection and change path is muscle memory, then continue the track.

Interview Questions

1. What does terraform init download and create?
2. Why separate plan and apply in team workflows?
3. What does terraform validate check versus terraform plan?
4. Why must destroy be treated as carefully as apply in shared environments?
5. What files should normally be committed versus ignored?

Sample answer — question 2

Plan shows the proposed changeset without mutating (unless using certain targets). Applying a saved plan ensures CI applies exactly what was reviewed, reducing surprise drift between plan and apply.

Sample answer — question 4

Destroy removes managed resources and can delete data. In shared environments it needs the same approvals, state locking awareness, and backups as any production change.

Related Tutorials

• Course overview
• Terraform Workflow: Init, Plan, Apply

References

• Install Terraform
• Terraform Registry