terraform/website/source/docs/providers/random/r/id.html.md

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---
layout: "random"
page_title: "Random: random_id"
sidebar_current: "docs-random-resource-id"
description: |-
Generates a random identifier.
---
# random\_id
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](../index.html) for more information.
## Attributes Reference
The following attributes are exported:
* `b64` - The generated id presented in base64, using the URL-friendly character set: case-sensitive letters, digits and the characters `_` and `-`.
* `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.