tfautomv

June 6, 2025 · View on GitHub

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Generate moved blocks and state move commands automatically for Terraform, OpenTofu, and Terragrunt.

Why?

tfautomv (a.k.a Terraform auto-move) is a refactoring helper. With it, making structural changes to your Terraform codebase becomes much easier.

When you move a resource in your code, Terraform loses track of the resource's state. The next time you run Terraform, it will plan to delete the resource it has memory of and create the "new" resource it found in your refactored code.

tfautomv inspects the output of terraform plan, detects such creation/deletion pairs and writes a moved block so that Terraform now knows no deletion or creation is required.

We explain why we built tfautomv in more detail in this blog article.

Here's a quick view of what tfautomv does:

demo

Best Practices

tfautomv is designed for refactoring scenarios where you want to restructure your Terraform code without changing the actual infrastructure. Understanding this distinction is crucial for successful usage.

✅ Good use cases (pure refactoring)

  • Renaming resources: aws_instance.web → aws_instance.web_server
  • Moving resources between modules: aws_instance.web → module.ec2.aws_instance.web
  • Changing resource organization: Converting single resources to for_each loops
  • Module restructuring: Moving resources between different modules

❌ Problematic use cases (infrastructure changes)

  • Changing resource configuration: Removing or adding attributes like tags, security_groups, etc.
  • Combining refactoring with configuration changes: Renaming AND modifying attributes in the same operation
  • Provider-specific transformations: Changes where the provider modifies attribute values
  1. First, make structural changes only: Rename resources, move between modules, or restructure without changing any resource attributes
  2. Run tfautomv: Generate the appropriate moved blocks or terraform state mv commands
  3. Apply the moves: This should result in an empty or minimal plan showing no infrastructure changes
  4. Then make configuration changes: In a separate step, modify resource attributes as needed

This approach ensures that moves represent safe refactoring operations separate from infrastructure changes.

Requirements

tfautomv uses the Terraform CLI command under the hood. This allows it to work with any Terraform version reliably.

Certain features require specific versions of Terraform:

  • moved blocks require Terraform v1.1 or above
  • cross-module terraform state mv commands require Terraform v0.14 or above
  • single-module terraform state mv commands require Terraform v0.13 or above

Installation

Contributions to support other installation methods are welcome!

Homebrew

On MacOS or Linux:

brew install busser/tap/tfautomv

Yay

On Arch Linux:

yay tfautomv-bin

asdf

With asdf version manager:

asdf plugin add tfautomv https://github.com/busser/asdf-tfautomv.git

Shell script

On MacOS or Linux:

curl -sSfL https://raw.githubusercontent.com/busser/tfautomv/main/install.sh | sh

This script can probably support Windows with a small amount of work. Contributions welcome!

Download

On the Github repository's Releases page, download the binary that matches your workstation's OS and CPU architecture.

Put the binary in a directory present in your system's PATH environment variable.

From source

You must have Go 1.18+ installed to compile tfautomv.

Clone the repository and build the binary:

git clone https://github.com/busser/tfautomv
cd tfautomv
make build

Then, move bin/tfautomv to a directory resent in your system's PATH environment variable.

Usage

Quick Start

Basic usage - run in any directory where you would run terraform plan:

tfautomv

This will run terraform init, terraform refresh, and terraform plan, then write moved blocks to a moves.tf file.

You can also target a specific working directory:

tfautomv ./production

Core Features

Generating moved blocks

By default, tfautomv generates moved blocks when possible:

tfautomv

Force moved blocks only with the --output=blocks flag:

tfautomv --output=blocks

Generating terraform state mv commands

Force terraform state mv commands only with the --output=commands flag:

tfautomv --output=commands

This will print commands to standard output. You can copy and paste them to a terminal to run them manually.

Alternatively, you can write the commands to a file:

tfautomv --output=commands > moves.sh

Or pipe them into a shell to run them immediately:

tfautomv --output=commands | sh

The -o flag is shorthand for --output:

tfautomv -o commands

Finding moves across multiple directories

If you have multiple Terraform modules in different directories, you can pass those directories to tfautomv:

tfautomv ./production/main ./production/backup -o commands

This will run terraform init, terraform refresh, and terraform plan in each directory, and then write terraform state mv commands to standard output. These commands will move resources within and across directories as needed.

Terraform does not natively support moving resources across directories. To achieve this, tfautomv will output commands that pull copies of each directory's state, perform the moves, and then push the new state back to the directory's state backend.

You can pass as many directories as you want to tfautomv.

This is only compatible with the commands output format. Terraform's moved block syntax does not support moving resources across directories.

Advanced Features

Performance optimization

By default, tfautomv runs Terraform's init, refresh, and plan steps. To save time, you can skip the init or refresh steps with the --skip-init and --skip-refresh flags:

tfautomv --skip-init --skip-refresh

The -s flag is shorthand for --skip-init and -S for `--skip-refresh:

tfautomv -sS

Debugging and verbosity

If you are not seeing a moved block for a resource you expected to be moved, you can increase tfautomv's verbosity with the -v flag to get more information:

tfautomv -v

The default verbosity level is 0. You can increase the verbosity up to 3 by repeating the -v flag:

tfautomv -vvv

Alternatively, you can specify a specific verbosity level with the --verbosity flag:

tfautomv --verbosity=2

Based on why the resource was not moved, you can choose to edit your code, write a moved block manually, or use the -ignore flag to ignore certain differences.

level 0 (default)level 1 (-v)level 2 (-vv)level 3 (-vvv)
verbosity level 0verbosity level 1verbosity level 2verbosity level 3

Ignoring certain differences

tfautomv works by comparing resources Terraform plans to create (those in your code) to those Terraform plans to delete (those in your state). Sometimes, tfautomv may not be able to match two resources together because of a difference in a specific attribute, even though the resources are in fact the same. This usually happens when the Terraform provider that manages the resource has transformed the attribute's value in some way.

In those cases, you can use the -ignore flag to ignore specific differences. tfautomv will ignore differences based on a set of rules that you can provide.

⚠️ Important considerations when using --ignore

The --ignore flag tells tfautomv to act as if certain attributes don't exist when comparing resources. While powerful, this comes with risks:

  • Risk of incorrect matches: If ignored attributes are actually important for identifying the correct resource pairing, tfautomv may match unrelated resources or fail to find matches
  • Intended for provider quirks: Use primarily when providers transform attribute values in ways that don't reflect actual infrastructure changes
  • Not for configuration changes: Avoid using --ignore to force matches when you've intentionally changed resource configuration

Good use cases for --ignore:

  • Provider transforms whitespace in policy documents
  • Provider adds computed fields that weren't in the original configuration
  • Provider normalizes values (e.g., adding default ports to security group rules)

Problematic use cases for --ignore:

  • Forcing matches when you've intentionally changed tags, security groups, or other meaningful attributes
  • Ignoring differences that represent real infrastructure changes you made

Each rule includes:

  • A kind that identifies the nature of the difference to ignore
  • A resource type the rule applies to
  • An attribute inside the resource the rule applies to
  • Optionally, additional arguments specific to the class

A rule is written as a colon-separated string:

<KIND>:<RESOURCE TYPE>:<ATTRIBUTE NAME>[:<KIND ARGUMENTS>]

You can use the --ignore flag multiple times to provide multiple rules:

tfautomv \
  --ignore="whitespace:azurerm_api_management_policy:xml_content" \
  --ignore="prefix:google_storage_bucket_iam_member:bucket:b/"

If you have a use case that is not covered by existing kinds, please open an issue so we can track demand for it.

The everything kind

Use the everything kind to ignore any difference between two values of an attribute:

tfautomv --ignore="everything:<RESOURCE TYPE>:<ATTRIBUTE>"

For example:

tfautomv --ignore="everything:random_pet:length"

The whitespace kind

Use the whitespace kind to ignore differences in whitespace between two values of an attribute:

tfautomv --ignore="whitespace:<RESOURCE TYPE>:<ATTRIBUTE NAME>"

For example, this rule:

tfautomv --ignore="whitespace:azurerm_api_management_policy:xml_content"

will allow these two resources to match:

# This resource has its XML nicely formatted.
resource "azurerm_api_management_policy" "foo" {
  api_management_id = "..."

  xml_content = <<-EOT
  <policies>
    <inbound>
      <cross-domain />
      <base />
      <find-and-replace from="xyz" to="abc" />
    </inbound>
  </policies>
  EOT
}

# This resource has its XML on one line.
resource "azurerm_api_management_policy" "bar" {
  api_management_id = "..."

  xml_content = "<policies><inbound><cross-domain /><base /><find-and-replace from=\"xyz\" to=\"abc\" /></inbound></policies>"
}

The prefix kind

Use the prefix kind to ignore a specific prefix between in one of two values of an attribute:

tfautomv --ignore="prefix:<RESOURCE TYPE>:<ATTRIBUTE NAME>:<PREFIX>"

For example:

tfautomv --ignore="prefix:google_storage_bucket_iam_member:bucket:b/"

will strip the b/ prefix from the bucket attribute of any google_storage_bucket_iam_member resources before comparing the attirbute's values.

Referencing nested attributes

Join parent attributes with child attributes with a .:

<KIND>:<RESOURCE TYPE>:parent_obj.child_field
<KIND>:<RESOURCE TYPE>:parent_list.0

To get an attribute's full path, increase the verbosity level with the -v flag:

tfautomv -vvv

Examples: When to use and avoid --ignore

✅ Good example - Provider-transformed attribute:

# Provider normalizes JSON policy formatting
tfautomv --ignore="whitespace:aws_iam_policy:policy"

✅ Good example - Provider adds computed fields:

# Provider adds computed "arn" or "id" fields that weren't in configuration
tfautomv --ignore="everything:aws_s3_bucket:arn"

❌ Problematic example - Intentional configuration change:

# DON'T do this - you've intentionally changed tags
# This forces a match that may result in unintended infrastructure changes
tfautomv --ignore="everything:aws_instance:tags"

# Instead: Apply moves first, then change tags in a separate operation

❌ Problematic example - Mixing refactoring with changes:

# Before (applied to infrastructure):
resource "aws_instance" "web" {
  ami           = "ami-12345"
  instance_type = "t2.micro"
  tags = {
    Environment = "prod"
    Team        = "backend"
  }
}

# After (refactored AND changed):
resource "aws_instance" "web_server" {  # renamed
  ami           = "ami-12345"
  instance_type = "t2.micro"
  tags = {
    Environment = "production"  # changed value
    Team        = "backend"
    Project     = "website"     # added new tag
  }
}

# DON'T use --ignore here - this mixes refactoring with real changes
# Instead: rename first, apply moves, then modify tags separately

Tool Integration

Passing additional arguments to Terraform

You can pass additional arguments to Terraform by using Terraform's built-in TF_CLI_ARGS and TF_CLI_ARGS_name environment variables..

For example, in order to use a file of variables during Terraform's plan:

TF_CLI_ARGS_plan="-var-file=production.tfvars" tfautomv

Using Terragrunt instead of Terraform

You can tell tfautomv to use the Terragrunt CLI instead of the Terraform CLI with the --terraform-bin flag:

tfautomv --terraform-bin=terragrunt

Using OpenTofu instead of Terraform

OpenTofu is officially supported! You can use OpenTofu with the --terraform-bin flag:

tfautomv --terraform-bin=tofu

This works with all tfautomv features including moved blocks, tofu state mv commands, and the --preplanned flag.

Using other Terraform-compatible tools

The --terraform-bin flag works with any executable that has an init and plan command compatible with Terraform.

Enterprise & CI/CD

Using existing plan files

If you have already generated Terraform plan files, you can use them directly with the --preplanned flag instead of having tfautomv run terraform plan. This is useful for:

  • Performance: Avoid re-running expensive plan operations when iterating on --ignore rules
  • Enterprise environments: Where running terraform locally is complex due to secrets or remote state
  • CI/CD workflows: Where plans are generated in earlier pipeline stages
  • Remote workspaces: TFE/Cloud environments where you can download JSON plans but can't run terraform locally

Single directory with default plan file

First generate a plan file, then run tfautomv:

terraform plan -out=tfplan.bin
tfautomv --preplanned

Single directory with custom plan file

terraform plan -out=my-plan.bin
tfautomv --preplanned --preplanned-file=my-plan.bin

Multiple directories

Each directory must have its own plan file:

# Generate plans in each directory
(cd production && terraform plan -out=tfplan.bin)
(cd staging && terraform plan -out=tfplan.bin)

# Run tfautomv across both directories
tfautomv --preplanned production staging

JSON vs binary plan files

tfautomv automatically detects the plan file format:

  • Binary plans (default): tfautomv runs terraform show -json to convert them
  • JSON plans (.json extension): tfautomv reads them directly
# Binary plan (requires terraform show conversion)
terraform plan -out=tfplan.bin
tfautomv --preplanned

# JSON plan (read directly) - useful for CI/CD or when you already have JSON
terraform plan -out=tfplan.bin
terraform show -json tfplan.bin > tfplan.json
tfautomv --preplanned --preplanned-file=tfplan.json

Important: When using --preplanned, all specified directories must have the plan file. If any directory is missing its plan file, tfautomv will exit with an error.

Disabling colors in output

Add the --no-color flag to your tfautomv command to disable output formatting like colors, bold text, etc.

For example:

tfautomv --no-color

Alternatively, you can achieve the same result by setting the NO_COLOR environment variable to any value:

NO_COLOR=true tfautomv

Thanks

Thanks to Padok, where this project was born 💜

License

The code is licensed under the permissive Apache v2.0 license. Read this for a summary.