Note_Tech

All technological notes.

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Terraform - Resource & Data source

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• Terraform - Resource \& Data source
  • Resource
  • Data Source
  • Lab: Ubuntu AMI Data

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Resource

• Resource

  • used to represent the infrastructure objects managed by terraform.

• During terraform apply, terraform will

  • Refresh the data sources
  • Create resources defined in *.tf files but not in the state file.
  • Destroy resources exist in the state file but not in *.tf files.
  • Update resrouces with different arguments in *.tf files than on the infrastructure.
    • Destroy and re-create mode:
      • most case, due to the limitation of the provider API.
      • ie.update user data will destroy first before recreate instance
    • In-place updates mode:
      • possible if provider API supports.
      • ie. update of security group without destroy

• reference of a resource:

  • RESOURCE_TYPE.NAME.ATTRIBUTE

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Data Source

• Data source

  • used to fetch or compute the data managed outside of terraform.
  • ie, AMI id, vpc id.
  • represents the existing infrastructure objects not managed by terraform.

• reference of a data source:

  • data.RESOURCE_TYPE.NAME.ATTRIBUTE

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Lab: Ubuntu AMI Data

provider "aws" {
  region = "ca-central-1"
}

data "aws_ami" "ubuntu_ami" {
  most_recent = true

  region = "ca-central-1"

  filter {
    name   = "name"
    values = ["ubuntu/images/hvm-ssd-gp3/ubuntu-noble-24.04-amd64-server-*"]
  }

  filter {
    name   = "virtualization-type"
    values = ["hvm"]
  }

  owners = ["099720109477"] # Canonical
}

output "ami_id" {
  value = data.aws_ami.ubuntu_ami.image_id
}


resource "aws_instance" "ec2_instance" {
  instance_type = "t2.micro"
  ami           = data.aws_ami.ubuntu_ami.id
}