example.tf

#--------------------------------------------------------------
# Instance
#--------------------------------------------------------------
resource "aws_instance" "main" {
    instance_type = "t2.micro"

    # Trusty 14.04
    ami = "ami-2a734c42"

    # This will create 1 instances
    count = 1

    subnet_id = "${aws_subnet.main.id}"
    security_groups = ["${aws_security_group.allow_all.id}"]
}

#--------------------------------------------------------------
# Security Group
#--------------------------------------------------------------
resource "aws_security_group" "allow_all" {
  name = "allow_all"
  description = "Allow all inbound traffic"
  vpc_id = "${aws_vpc.main.id}"

  ingress {
      from_port = 0
      to_port = 0
      protocol = "-1"
      cidr_blocks = ["0.0.0.0/0"]
  }
}

#--------------------------------------------------------------
# VPC
#--------------------------------------------------------------
resource "aws_vpc" "main" {
    cidr_block = "172.31.0.0/16"
    enable_dns_hostnames = true
}

resource "aws_subnet" "main" {
    vpc_id = "${aws_vpc.main.id}"
    cidr_block = "172.31.0.0/20"
    map_public_ip_on_launch = true
}

resource "aws_internet_gateway" "gw" {
    vpc_id = "${aws_vpc.main.id}"
}

resource "aws_route_table" "r" {
    vpc_id = "${aws_vpc.main.id}"
    route {
        cidr_block = "0.0.0.0/0"
        gateway_id = "${aws_internet_gateway.gw.id}"
    }
}

resource "aws_main_route_table_association" "a" {
    vpc_id = "${aws_vpc.main.id}"
    route_table_id = "${aws_route_table.r.id}"
}