Name	Name	Last commit message	Last commit date
parent directory ..
imgs	imgs
00_provider.tf	00_provider.tf
01_backend.tf	01_backend.tf
02_variables.tf	02_variables.tf
03_vpc.tf	03_vpc.tf
README.md	README.md

Terraform Refresh

Terraform `refresh` command

The terraform refresh command is used to update the state file of your terraform project (desired state) with the real-world infrastructure (current state).
When you run terraform refresh command, Terraform queries the actual state of your infrastructure and compares it with the state file that it maintains locally or remotely.
The terraform refresh command synchronizes the Terraform state with the real-world state of your infrastructure.

What happens when you run `terraform refresh` command ?

Queries Infrastructure: Terraform communicates with the provider (e.g., AWS, Azure) to retrieve the current state of all resources defined in your configuration.
Compares with State File: It compares the current state of the infrastructure with the state stored in the state file.
Updates State File: Any differences found between the real-world infrastructure and the state file are updated in the state file.
Doesn't Modify Infrastructure: Unlike terraform apply, terraform refresh only updates the state file and does not make any changes to the actual infrastructure.

When to use `terraform refresh` command

After External Changes: Use terraform refresh when you suspect that changes have been made to your infrastructure outside of Terraform.
Before Applying Changes: It's often a good idea to run terraform refresh before terraform apply to ensure that your Terraform configuration is based on the most up-to-date information

Example:

Lets Create A Simple VPC and learn about terraform refresh command

00_provider.tf

terraform {
  required_providers {
    aws = {
      source  = "hashicorp/aws"
      version = "~> 5.0"
    }
  }
}

provider "aws" {
  region = var.aws_region

  default_tags {
    tags = {
      Terraform = "yes"
      Owner     = var.owner
    }
  }
}

01_backend.tf

terraform {
  backend "s3" {
    bucket         = "tf-aws-backend"
    key            = "tf/dev/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "tf-dev-state-lock"
  }
}

02_variables.tf

variable "aws_region" {
  description = "AWS Region In Which Resources will be Created"
  type        = string
  default     = "us-east-1"
}

variable "owner" {
  description = "Name of the Engineer who is creating Resources"
  type        = string
  default     = "Venkatesh"
}

03_vpc.tf

resource "aws_vpc" "myvpc" {
  cidr_block = "10.0.0.0/16"

  tags = {
    Name = "MyVPC"
  }
}

In the above example,
- We are trying to Create A Simple VPC via terraform
- Manually add additional tag Department = FinOps to VPC from AWS Console
- Observe the behavior w.r.t terraform refresh

Lets Execute Terraform commands to understand data source behavior

terraform init : Initialize terraform
terraform validate : Validate terraform code
terraform fmt : format terraform code
terraform plan : Review the terraform plan
terraform apply : Create Resources by terraform

terraform apply

PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform apply -auto-approve
Acquiring state lock. This may take a few moments...

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
+ create

Terraform will perform the following actions:

# aws_vpc.myvpc will be created
+ resource "aws_vpc" "myvpc" {
    + arn                                  = (known after apply)
    + cidr_block                           = "10.0.0.0/16"
    + default_network_acl_id               = (known after apply)
    + default_route_table_id               = (known after apply)
    + default_security_group_id            = (known after apply)
    + dhcp_options_id                      = (known after apply)
    + enable_dns_hostnames                 = (known after apply)
    + enable_dns_support                   = true
    + enable_network_address_usage_metrics = (known after apply)
    + id                                   = (known after apply)
    + instance_tenancy                     = "default"
    + ipv6_association_id                  = (known after apply)
    + ipv6_cidr_block                      = (known after apply)
    + ipv6_cidr_block_network_border_group = (known after apply)
    + main_route_table_id                  = (known after apply)
    + owner_id                             = (known after apply)
    + tags                                 = {
        + "Name" = "MyVPC"
        }
    + tags_all                             = {
        + "Name"      = "MyVPC"
        + "Owner"     = "Venkatesh"
        + "Terraform" = "yes"
        }
    }

Plan: 1 to add, 0 to change, 0 to destroy.
aws_vpc.myvpc: Creating...
aws_vpc.myvpc: Creation complete after 3s [id=vpc-0ce1484586ef17bf0]
Releasing state lock. This may take a few moments...

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

You can now find AWS Console the VPC with CIDR 10.0.0.0/16 created. Now lets Manually add additional tag Department = FinOps and than run terraform plan to see how terraform detects the change and implies to remove the manual changes.

terraform plan : Detects the change and implies to remove the manual changes

terraform plan

PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform plan
Acquiring state lock. This may take a few moments...
aws_vpc.myvpc: Refreshing state... [id=vpc-0ce1484586ef17bf0]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
~ update in-place

Terraform will perform the following actions:

# aws_vpc.myvpc will be updated in-place
~ resource "aws_vpc" "myvpc" {
        id                                   = "vpc-0ce1484586ef17bf0"
    ~ tags                                 = {
        - "Department" = "FinOps" -> null
            "Name"       = "MyVPC"
        }
    ~ tags_all                             = {
        - "Department" = "FinOps" -> null
            # (3 unchanged elements hidden)
        }
        # (14 unchanged attributes hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.

Now lets run terraform refresh command to synchronize real infra (current state) with terraform tf files (desired state)

    PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform refresh
    Acquiring state lock. This may take a few moments...
    aws_vpc.myvpc: Refreshing state... [id=vpc-0ce1484586ef17bf0]
    Releasing state lock. This may take a few moments...
    PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh>

Now lets run terraform show command to see the new tag Department = FinOps updated to terraform state file

PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform show
# aws_vpc.myvpc:
resource "aws_vpc" "myvpc" {
    arn                                  = "arn:aws:ec2:us-east-1:520974589522:vpc/vpc-0ce1484586ef17bf0"
    assign_generated_ipv6_cidr_block     = false
    cidr_block                           = "10.0.0.0/16"
    default_network_acl_id               = "acl-008d6f0c48dbb7170"
    default_route_table_id               = "rtb-09b93a8f5486a6f76"
    default_security_group_id            = "sg-0418ad85d2ece013a"
    dhcp_options_id                      = "dopt-7c9cef04"
    enable_dns_hostnames                 = false
    enable_dns_support                   = true
    enable_network_address_usage_metrics = false
    id                                   = "vpc-0ce1484586ef17bf0"
    instance_tenancy                     = "default"
    ipv6_netmask_length                  = 0
    main_route_table_id                  = "rtb-09b93a8f5486a6f76"
    owner_id                             = "520974589522"
    tags                                 = {
        "Department" = "FinOps"
        "Name"       = "MyVPC"
    }
    tags_all                             = {
        "Department" = "FinOps"
        "Name"       = "MyVPC"
        "Owner"      = "Venkatesh"
        "Terraform"  = "yes"
    }
}

Please Note :
- terraform refresh command only updates the state file and does not really import the new changes to existing code.
- If you want to include the new changes into the code as well than you will have to update the code manually as well.

terraform plan : Would still detects the change and implies to remove the manual changes, running terraform apply will certainly remove any manual changes into infra.

PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform plan
Acquiring state lock. This may take a few moments...
aws_vpc.myvpc: Refreshing state... [id=vpc-0ce1484586ef17bf0]

Terraform used the selected providers to generate the following execution plan. Resource actions are indicated with the following symbols:
~ update in-place

Terraform will perform the following actions:

# aws_vpc.myvpc will be updated in-place
~ resource "aws_vpc" "myvpc" {
        id                                   = "vpc-0ce1484586ef17bf0"
    ~ tags                                 = {
        - "Department" = "FinOps" -> null
            "Name"       = "MyVPC"
        }
    ~ tags_all                             = {
        - "Department" = "FinOps" -> null
            # (3 unchanged elements hidden)
        }
        # (14 unchanged attributes hidden)
    }

Plan: 0 to add, 1 to change, 0 to destroy.

So to conclude, if you have any manual changes to your AWS infrastructure than you have 2 Choices to make

1. If you do not want the manual changes, you can run terraform apply and it will certainly remove any manual changes into infra.

2. If you want to retain the manual changes, than you will have to update your terraform code as well to incorporate the same changes.

Example : Lets update new tag Department = FinOps to our 03_vpc.tf file and run terraform plan again
```
resource "aws_vpc" "myvpc" {
cidr_block = "10.0.0.0/16"

tags = {
    Name = "MyVPC"
    Department = "FinOps"
}
}
```

terraform plan : now shows there is No changes. Your infrastructure matches the configuration.

PS D:\StudyRelated\terraform-beginners-guide\14-Terraform-Refresh> terraform plan
Acquiring state lock. This may take a few moments...
aws_vpc.myvpc: Refreshing state... [id=vpc-0ce1484586ef17bf0]

No changes. Your infrastructure matches the configuration.

Terraform has compared your real infrastructure against your configuration and found no differences, so no changes are needed.
Releasing state lock. This may take a few moments...

References :

Terraform Refresh : https://developer.hashicorp.com/terraform/cli/commands/refresh

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

14-Terraform-Refresh

14-Terraform-Refresh

README.md

Terraform Refresh