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.

HCL Syntax

Basic Syntax

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

Full Syntax

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

Fields

Field	Type	Required	Description
byte_length	int	✓	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 Name Generation

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

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

  # Use random ID to ensure unique container names
  meta {
    name = "web-${resource.random_id.container_suffix.hex}"
  }
}

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 Naming

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

Common Use Cases

1. Unique Naming: Generating unique suffixes for resource names
2. Session IDs: Creating session identifiers for applications
3. Database Names: Generating unique database or schema names
4. Cache Keys: Creating cache key prefixes or suffixes
5. API Keys: Generating non-sensitive API identifiers
6. Container Names: Ensuring unique container names in multi-instance deployments
7. Network Isolation: Creating unique network identifiers