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23 - Host with DNS ​

Working Code: terraform/exercise-23-dns-host/

The Problem: In Exercise 16, we fixed "Unknown Host" by scanning the IP. But if you recreate the server, the IP changes and you must find the new one.

The Solution: Use a DNS name (e.g., workhorse.g2...) for SSH. The name stays the same even if the IP changes.

Objective ​

Update SSH wrapper and known_hosts to use the server's DNS name instead of IP.

How-to ​

1. Create DNS Record ​

hcl
resource "dns_a_record_set" "workhorse" {
  zone = "sdi.hdm-stuttgart.cloud."
  name = "workhorse.g2"
  addresses = [hcloud_server.workhorse.ipv4_address]
}

2. Update ssh-keyscan ​

hcl
provisioner "local-exec" {
  command = <<EOT
    sleep 10  # DNS propagation
    ssh-keyscan workhorse.g2.sdi.hdm-stuttgart.cloud > gen/known_hosts
  EOT
}

3. Update Wrapper Template ​

bash
#!/usr/bin/env bash

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

ssh -o UserKnownHostsFile="$GEN_DIR/known_hosts" devops@workhorse.g2.sdi.hdm-stuttgart.cloud "$@"

Verification ​

bash
terraform apply
./bin/ssh  # Connects via hostname
# Destroy/recreate → IP changes but ./bin/ssh still works