Creating Host With Corresponding DNS entries

Technical Background

Solution

Prerequisits

Create the same files and folder structure as done before in exercise 19 Creating DNS Records.

Configuring Known Host Generator

1. Add DNS Zone and Server Name Variable to /Module/SshKnownHosts/variables.tf:

variable "dnsZone" {
  type        = string
  description = "DNS Zone of the server"
}

variable "serverName" {
  type        = string
  description = "name of the server"
}

1. Update the Known Host Wrapper ressource in /Module/SshKnownHosts/main.tf:

resource "local_file" "known_hosts" {
  content         = "${var.serverName}.${var.dnsZone} ${var.public_key}"
  filename        = "gen/known_hosts"
  file_permission = "644"
}

1. Add variables in /KnownHostsByModule/main.tf to üass the DNS Zone and Server Name to Module from parent:

module "createSshKnownHosts" {
  source              = "../Module/SshKnownHosts"
  loginName           = hcloud_ssh_key.loginUser.name
  ip4Address          = hcloud_server.web.ipv4_address
  public_key          = local_file.server_public_key.content
  dnsZone             = var.dns_zone
  serverName          = var.server_name
}

Use DNS Name instead of IP in ssh.sh

1. Create Variable that replaces old ip variable and combines and stores DNS Name and DNS Zone inside local_file ressource for ssh.sh:

resource "local_file" "ssh_script" {
  content = templatefile("${path.module}/tpl/ssh.sh", {
    dns = "${var.serverName}.${var.dnsZone}"
    loginName = "${var.loginName}"
  })
  filename = "bin/ssh"
  file_permission = "700"
  depends_on      = [local_file.known_hosts]
}

1. Replace ip with dns inside the ssh.sh template:

#!/usr/bin/env bash

GEN_DIR=$(dirname "$0")/../gen

ssh \
  -o UserKnownHostsFile="$GEN_DIR/known_hosts" \
  -o IdentitiesOnly=yes \
  -i ~/.ssh/id_ed25519 \
  ${loginName}@${dns}

Deploy and Verify

Initialize and apply Terraform inside /KnownHostsByModule:

terraform init
terraform apply

Related Links

DNS

Terraform Variables

DNS Record Types

Terraform Count

Terraform Validation Rules

Terraform Distinct Function

Terraform Contains