Demo Migrating existing Terraform configuration to OpenTofu

• Applying the initial Terraform configuration
• Installing OpenTofu
• Backing up state files
• Initializing and planning with OpenTofu
• Updating resources and applying changes
• Rolling back to Terraform

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1. Apply the Initial Terraform Configuration

1. Navigate to your project directory and review main.tf:
   resource "local_file" "file" {
     filename = "terraform.txt"
     content  = "This file has been created with Terraform"
   }
   
2. Initialize and apply:
   cd ~/opentofu-projects/migration
   terraform init
   terraform apply
   
3. When prompted, enter yes. You should see:
   local_file.file: Creating...
   local_file.file: Creation complete after 0s [id=342bd3c96f4da9100a6360378942400b96bfb5]
   Apply complete! Resources: 1 added, 0 changed, 0 destroyed.
   
4. Verify that terraform.txt exists with the correct content.

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2. Install OpenTofu

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Automated Debian/Ubuntu Installer

curl --proto '=https' --tlsv1.2 -fsSL https://get.opentofu.org/install-opentofu.sh -o install-opentofu.sh
chmod +x install-opentofu.sh
./install-opentofu.sh --install-method deb
rm install-opentofu.sh

#!/bin/bash
curl --proto '=https' --tlsv1.2 -fsSL https://get.opentofu.org/install-opentofu.sh -o install-opentofu.sh
chmod +x install-opentofu.sh
./install-opentofu.sh --install-method deb
rm install-opentofu.sh

chmod +x install.sh
./install.sh

tofu version

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3. Backup the Terraform State

tar czf terraform.tfstate.tar.gz terraform.tfstate

ls
# install.sh  main.tf  terraform.tfstate  terraform.tfstate.tar.gz

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4. Initialize with OpenTofu

tofu init

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5. Preview the OpenTofu Plan

tofu plan

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6. Update the main.tf for OpenTofu

resource "local_file" "file" {
  filename = "opentofu.txt"
  content  = "This file has been created with OpenTofu"
}

tofu validate

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7. Apply with OpenTofu

tofu apply

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8. Roll Back to Terraform

1. Backup the OpenTofu state:
   tar czf terraform.tfstate.tar.gz terraform.tfstate
   
2. Re-initialize with Terraform:
   terraform init
   

3. Revert main.tf to the original Terraform resource:
   resource "local_file" "file" {
     filename = "terraform.txt"
     content  = "This file has been created with Terraform"
   }
   
4. Apply with Terraform:
   terraform apply
   
   Enter yes and observe:
   Plan: 1 to add, 0 to change, 1 to destroy.
   Enter a value: yes
   local_file.file: Destroying... [id=91b198b8059c5f72782d9c1d1fe18f6d]
   local_file.file: Destruction complete after 0s
   local_file.file: Creating...
   local_file.file: Creation complete after 0s [id=342bd3c9e4fda9100a36097894200e96b]
   Apply complete! Resources: 1 added, 0 changed, 1 destroyed.
   

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Links and References

• Terraform Documentation
• OpenTofu Getting Started
• Terraform local_file Resource