Random ID

The random_id resource generates cryptographically secure random identifiers. It provides the generated ID in multiple formats (base64, hexadecimal, and decimal) for use in other resources and configurations.

Use Cases

As a lab author, you can use random_id resources to:

• Unique Resource Naming: Generate unique suffixes for container names, network names, and other resources to prevent conflicts
• Dynamic Configuration: Generate unique keys, tokens, or identifiers for application configuration files

Random ID resources ensure uniqueness and prevent resource conflicts in lab environments while maintaining idempotency.

HCL Syntax

Basic Syntax

resource "random_id" "name" {
  byte_length = 8
}

Full Syntax

resource "random_id" "name" {
  byte_length = 16
}

Fields

Field	Required	Type	Description
byte_length	✓	int64	Number of random bytes to generate (minimum: 1)

Computed Attributes

These attributes are set by the system after ID generation:

Field	Type	Description
base64	string	Generated ID in base64 encoding
hex	string	Generated ID in padded hexadecimal (twice the byte length)
dec	string	Generated ID in decimal format

Validation Rules

• Byte length must be at least 1
• Generated values remain constant across multiple runs (idempotent)
• Random values are cryptographically secure

Examples

Simple Random ID

resource "random_id" "session" {
  byte_length = 8
}

output "session_id" {
  value = resource.random_id.session.hex
}

Database Identifier

resource "random_id" "db_suffix" {
  byte_length = 4
}

resource "container" "database" {
  image {
    name = "postgres:15"
  }

  environment = {
    POSTGRES_DB = "app_${resource.random_id.db_suffix.hex}"
  }
}

Multiple Format Usage

resource "random_id" "app_key" {
  byte_length = 32
}

# Use in different formats
output "key_base64" {
  value = resource.random_id.app_key.base64
  description = "Application key in base64 format"
}

output "key_hex" {
  value = resource.random_id.app_key.hex
  description = "Application key in hex format"
}

output "key_decimal" {
  value = resource.random_id.app_key.dec
  description = "Application key in decimal format"
}

Container Environment Variables

resource "random_id" "container_suffix" {
  byte_length = 6
}

resource "container" "web" {
  image {
    name = "nginx:alpine"
  }

  # Use random ID in environment variables
  environment = {
    INSTANCE_ID = resource.random_id.container_suffix.hex
    CONTAINER_SUFFIX = resource.random_id.container_suffix.base64
  }
}

Secret Generation

resource "random_id" "api_secret" {
  byte_length = 24
}

resource "template" "app_config" {
  source = <<-EOF
    api:
      secret_key: ${resource.random_id.api_secret.base64}
      session_timeout: 3600
  EOF

  destination = "./config/app.yaml"
}

Network Subnet Generation

resource "random_id" "network_id" {
  byte_length = 4
}

resource "network" "app_network" {
  subnet = "10.${resource.random_id.network_id.dec % 254 + 1}.0.0/24"
}

Best Practices

1. Appropriate Length: Use sufficient byte length for your use case (8-16 bytes for most identifiers)
2. Format Selection: Choose the appropriate format for your target system
3. Uniqueness: Random IDs are unique per resource instance, not globally unique
4. Security: Use for non-sensitive identifiers; for passwords use random_password
5. Naming: Use descriptive resource names to clarify the ID’s purpose
6. Consistency: Use the same format consistently within a configuration