Detecting infrastructure drift

Detecting Infrastructure Drift

Current State

!ls *.tf Dockerfile docker-compose.yml 2>/dev/null || echo 'No IaC files found' !terraform version 2>/dev/null || echo 'Terraform not installed'

Overview

Detect discrepancies between actual cloud infrastructure state and the desired state defined in IaC (Terraform, CloudFormation, Pulumi). Run drift detection commands, analyze modified/added/deleted resources, generate drift reports with affected resources, and provide remediation steps to bring infrastructure back into compliance.

Prerequisites

• IaC configuration files up to date in the project directory
• Cloud provider CLI installed and authenticated with read access to all managed resources
• IaC tool installed: Terraform 1.0+, AWS CLI (for CloudFormation drift), or Pulumi
• Remote state storage accessible and current (S3 backend, Terraform Cloud, Pulumi Cloud)
• Read-only IAM permissions for all resource types managed by IaC

Instructions

1. Identify the IaC tool in use by scanning for .tf files, template.yaml, or Pulumi.yaml
2. Initialize the IaC tool if needed: terraform init to download providers and configure backend
3. Run drift detection: terraform plan -detailed-exitcode (exit code 2 = drift detected), aws cloudformation detect-stack-drift, or pulumi preview
4. Parse the output to identify resources with drift: added (exists in cloud but not in IaC), modified (attributes changed), or deleted (in IaC but missing from cloud)
5. For each drifted resource, determine if the drift is intentional (manual hotfix) or unintentional (configuration error, unauthorized change)
6. Generate a structured drift report with resource identifiers, attribute differences, and severity classification
7. Provide remediation options per resource: terraform apply to enforce desired state, terraform import to adopt changes, or update IaC to match reality
8. Schedule recurring drift detection: configure a cron job or CI pipeline to run daily and alert on drift
9. Investigate the root cause: determine who made the manual change and implement guardrails (SCPs, IAM restrictions) to prevent recurrence

Output

• Drift detection report with resource-level detail: resource type, ID, drifted attributes, expected vs. actual values
• Remediation commands: terraform apply, terraform import, or IaC code updates
• CI/CD pipeline step for automated drift detection on a schedule
• Alert configuration for drift detection results (Slack, email, PagerDuty)
• Prevention recommendations: IAM policy restrictions, SCP guardrails, automated enforcement

Error Handling

Error	Cause	Solution
Error acquiring state lock	Another Terraform process is running or stale lock	Wait for the other process; use terraform force-unlock <ID> if the lock is stale
Unable to authenticate to cloud provider	Expired or missing credentials	Refresh with aws configure, gcloud auth login, or az login
No state file found	Backend not initialized or state file deleted	Run terraform init to configure the backend; restore state from backup if deleted
Access denied reading resource	IAM policy missing read permissions for some resource types	Grant read-only access for all resource types managed by IaC (ReadOnlyAccess or specific policies)
State file version mismatch	Terraform version newer than state format	Upgrade Terraform to match the state version or use terraform state replace-provider

Examples

• "Run drift detection against all Terraform-managed infrastructure and generate a report of resources that have changed since last apply."
• "Set up a daily GitHub Actions workflow that runs terraform plan and posts drift results to Slack if any resources are out of sync."
• "Detect CloudFormation stack drift for the production VPC stack and provide remediation steps for any MODIFIED resources."

Resources

• Terraform drift detection: https://developer.hashicorp.com/terraform/tutorials/state/resource-drift
• CloudFormation drift detection: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/detect-drift-stack.html
• Pulumi drift detection:
• Preventing drift: https://developer.hashicorp.com/terraform/tutorials/state/refresh