» random_id

The resource random_id generates random numbers that are intended to be used as unique identifiers for other resources.

This resource does use a cryptographic random number generator in order to minimize the chance of collisions, making the results of this resource when a 16-byte identifier is requested of equivalent uniqueness to a type-4 UUID.

This resource can be used in conjunction with resources that have the create_before_destroy lifecycle flag set to avoid conflicts with unique names during the brief period where both the old and new resources exist concurrently.

» Example Usage

The following example shows how to generate a unique name for an AWS EC2 instance that changes each time a new AMI id is selected.

resource "random_id" "server" {
  keepers = {
    # Generate a new id each time we switch to a new AMI id
    ami_id = "${var.ami_id}"

  byte_length = 8

resource "aws_instance" "server" {
  tags = {
    Name = "web-server ${random_id.server.hex}"

  # Read the AMI id "through" the random_id resource to ensure that
  # both will change together.
  ami = "${random_id.server.keepers.ami_id}"

  # ... (other aws_instance arguments) ...

» Argument Reference

The following arguments are supported:

  • byte_length - (Required) The number of random bytes to produce. The minimum value is 1, which produces eight bits of randomness.

  • keepers - (Optional) Arbitrary map of values that, when changed, will trigger a new id to be generated. See the main provider documentation for more information.

  • prefix - (Optional) Arbitrary string to prefix the output value with. This string is supplied as-is, meaning it is not guaranteed to be URL-safe or base64 encoded.

» Attributes Reference

The following attributes are exported:

  • b64_url - The generated id presented in base64, using the URL-friendly character set: case-sensitive letters, digits and the characters _ and -.
  • b64_std - The generated id presented in base64 without additional transformations.
  • hex - The generated id presented in padded hexadecimal digits. This result will always be twice as long as the requested byte length.
  • dec - The generated id presented in non-padded decimal digits.

» Import

Random Ids can be imported using the b64_url with an optional prefix. This can be used to replace a config value with a value interpolated from the random provider without experiencing diffs.

Example with no prefix: $ terraform import random_id.server p-9hUg

Example with prefix (prefix is separated by a ,): $ terraform import random_id.server my-prefix-,p-9hUg