Quick Answer
terraform init
That’s it in 90% of cases. Terraform needs to download/link modules before plan or apply.
The Error
Error: Module not installed
on main.tf line 10:
10: module "vpc" {
This module is not yet installed. Run "terraform init" to install all modules
required by this configuration.
What Causes This
- Never ran
terraform init— fresh clone, new module added .terraform/deleted — cleaned up cache, CI/CD fresh workspace- Module source changed — updated source URL but didn’t re-init
- Git submodule not cloned — source points to unresolved path
- Private registry auth missing — can’t download from private registry
Solution 1: Run terraform init
terraform init
This downloads all modules to .terraform/modules/.
If source changed, you may need:
terraform init -upgrade
Solution 2: Clean and Reinitialize
rm -rf .terraform .terraform.lock.hcl
terraform init
Solution 3: Fix Module Source Paths
Common source format mistakes:
# Local module — relative path from current directory
module "vpc" {
source = "./modules/vpc" # ✅ Correct
source = "modules/vpc" # ❌ Missing ./
source = "../shared/modules/vpc" # ✅ Relative path up
}
# Registry module — org/name/provider format
module "vpc" {
source = "terraform-aws-modules/vpc/aws" # ✅
version = "~> 5.0"
}
# Git module — double slash separates repo from subdirectory
module "vpc" {
source = "git::https://github.com/org/infra.git//modules/vpc?ref=v1.0" # ✅
source = "git::https://github.com/org/infra.git/modules/vpc?ref=v1.0" # ❌ Single slash
}
# GitHub shorthand
module "vpc" {
source = "github.com/org/terraform-modules//vpc?ref=v2.0" # ✅
}
Solution 4: Git Authentication for Private Modules
# SSH key (most common)
module "vpc" {
source = "git::ssh://git@gitlab.com/myorg/modules.git//vpc?ref=v1.0"
}
# Ensure SSH key is loaded
ssh-add ~/.ssh/id_rsa
ssh -T git@gitlab.com # Test connectivity
# HTTPS with token
module "vpc" {
source = "git::https://oauth2:${GITLAB_TOKEN}@gitlab.com/myorg/modules.git//vpc?ref=v1.0"
}
In CI/CD, configure Git credentials:
# GitLab CI
before_script:
- git config --global url."https://gitlab-ci-token:${CI_JOB_TOKEN}@gitlab.com/".insteadOf "https://gitlab.com/"
- terraform init
Solution 5: Private Registry Authentication
# ~/.terraformrc
credentials "app.terraform.io" {
token = "your-team-token"
}
credentials "gitlab.com" {
token = "your-gitlab-token"
}
Debugging
# See what modules are installed
ls -la .terraform/modules/
# Verbose init output
TF_LOG=DEBUG terraform init 2>&1 | grep -i module
# Verify module directory structure
find .terraform/modules/ -name "*.tf" | head -20
CI/CD: Cache Modules
Speed up pipelines by caching modules:
# GitLab CI
cache:
key: terraform-modules-${CI_COMMIT_REF_SLUG}
paths:
- .terraform/modules/
- .terraform/providers/
Hands-On Courses
- Terraform for Beginners on CopyPasteLearn
- Terraform By Example — practical code examples
Conclusion
Module not installed = run terraform init. If that doesn’t work, check the source path format (local needs ./, Git needs // double-slash for subdirectories), verify Git SSH/HTTPS authentication for private repos, and use terraform init -upgrade when source URLs change.