Hashicorp Configuration Language: Difference between revisions
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"default" may be "null" | Each variable can have a default value specified with "default". "default" may be "null". If there is no "default" declaration, Terraform will signal an error when terraform apply is executed, and it will initiate an interactive CLI that will inquire for the value of the missing variable: | ||
'''var.environment_name''' | |||
The name of the environment | |||
'''Enter a value:''' | |||
<syntaxhighlight lang='text'> | <syntaxhighlight lang='text'> |
Revision as of 22:11, 16 November 2019
External
Internal
Overview
Comments
# This is a comment
Block
Terraform Block
terraform {
required_version = ">= 0.12"
}
Resource Block
Declares a resource.
Data Block
Declares a data source.
data "data-source-name" "local-name" { ... }
data "aws_ami" "example" {
most_recent = true
owners = ["self", "0000000"]
filter {
name = "name"
values = ["consul-ubuntu-*"]
}
tags = {
Name = "app-server"
Tested = "true"
}
}
Module Block
Represents a module call.
References to Named Values or Interpolation Expression
Resource elements can be used by other resources via interpolation expressions:
resource "aws_subnet" "something" {
vpc_id = "${aws_vpc.main.id}"
...
}
Input Variable
variable "region" {
description = "This is the region"
type = string
default = "us-east-1"
}
Each variable can have a default value specified with "default". "default" may be "null". If there is no "default" declaration, Terraform will signal an error when terraform apply is executed, and it will initiate an interactive CLI that will inquire for the value of the missing variable:
var.environment_name The name of the environment Enter a value:
variable "masters" {
description = "The number of master nodes"
type = number
default = 1
}
Variables can be used via interpolation expression, prefixed with “var.”
To use the variable:
...
Name = "${var.playground_name}-playground-vpc"
...
Variables can be assigned in multiples way, and this is the descending order of precedence:
- command-line flags (-var = ‘region=something’)
- from a file (.tfvars, -var-file=…) terraform.tfvars or *.auto.tfvars in the current directory are automatically loaded. Multiple -var-file can be used.
- From environment variables: TF_VAR_name. This can only be used for string variables.
- UI Input
- Variable defaults (“default” keyword).
Lists
variable "security_groups" {
description = "The list of security groups"
type = list
default = ["sg-a41f9d51704199e97"]
}
Maps
Output Variable
Output variables are a way to organize data to be easily queried and shown back to the Terraform user. Terraform usually stores hundred or thousands of attribute values, but only a few of those are important. Output variables have several uses: a child module can use outputs to expose a subset of its resource attributes to a parent module, a root module ca use outputs to print certain values in the CLI output after running terraform apply
and when using remote state, module outputs can be accessed by other configurations via a terraform_remote_state
data source.
"Output value" and "output" are semantically equivalent.
An output is declared as:
output "bastion_public_ip" {
value = aws_instance.bastion.public_ip
description = "The public IP address of the bastion"
}
Also see:
Functions
Function Categories
String
substr
...
cidr_block = "${substr("${var.my_cidr_block}", 0, 5)}.1.0/24"
...
IP Network
cidrsubnet
The following turns "10.10.0.0/16" into its first /24 subnet "10.10.1.0/24"
...
cidr_block = "${cidrsubnet("${var.vpc_cidr_block}", 8, 1)}"
...