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

Unlike other resources in the "random" provider, 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 32-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.


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

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