The backend "s3" block in your main.tf or backend.tf file is used to configure this. Key parameters include:

• bucket: The name of your S3 bucket.
• key: The path and filename for the state file within the bucket (e.g., path/to/my/terraform.tfstate).
• region: The AWS region where the S3 bucket is located.
• dynamodb_table: The name of a DynamoDB table used for state locking. This table must be created separately and configured with a primary key named LockID (String type).

Example:

terraform {
  backend "s3" {
    bucket         = "my-terraform-state-bucket"
    key            = "global/s3/terraform.tfstate"
    region         = "us-east-1"
    dynamodb_table = "my-terraform-state-lock"
    encrypt        = true
  }
}

Ensure the AWS credentials used by Terraform have permissions to read/write to the S3 bucket and the DynamoDB table.

The backend "azurerm" block is used for configuration. Essential parameters include:

• storage_account_name: The name of your Azure Storage Account.
• container_name: The name of the blob container within the storage account.
• key: The name of the blob file to store the state (e.g., terraform.tfstate).
• access_key or sas_token: Credentials to authenticate with Azure Storage. It's recommended to use environment variables or managed identities for security.

Example:

terraform {
  backend "azurerm" {
    resource_group_name  = "my-resource-group"
    storage_account_name = "mystorageaccount"
    container_name       = "tfstate"
    key                  = "terraform.tfstate"
    use_azuread_auth     = true # Recommended for Azure AD authentication
  }
}

Ensure the Azure credentials have the necessary permissions (e.g., 'Storage Blob Data Contributor') on the storage account and container.

The backend "gcs" block requires:

• bucket: The name of your GCS bucket.
• prefix: The path to the state file within the bucket (e.g., path/to/terraform.tfstate).

Example:

terraform {
  backend "gcs" {
    bucket = "my-gcs-terraform-state-bucket"
    prefix = "terraform/state"
  }
}

Ensure the service account or user credentials used by Terraform have the 'Storage Object Admin' role on the specified bucket.

Instead of a backend "s3" or similar block, you typically use a cloud block:

terraform {
  cloud {
    organization = "my-terraform-cloud-org"

    workspaces {
      name = "my-project-workspace"
    }
  }
}

This configuration tells Terraform to use Terraform Cloud for state storage and management. Terraform Cloud handles state locking, versioning, and provides a web UI for managing runs. You'll need to authenticate with Terraform Cloud, usually via an API token.