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18 - SSH Module Refactor ​

Working Code: terraform/exercise-18-ssh-module/

The Problem: Exercise 16's SSH boilerplate (wrappers, known_hosts) gets copy-pasted everywhere.

The Solution: Encapsulate into a reusable Terraform module.

Objective ​

Move SSH logic from Exercise 16 into modules/SshKnownHosts.

How-to ​

1. Create Module ​

Move logic into modules/SshKnownHosts/main.tf with inputs: server_ip, devops_username.

2. Use Module ​

hcl
module "ssh_known_hosts" {
  source = "../modules/SshKnownHosts"

  server_ip       = hcloud_server.web.ipv4_address
  devops_username = var.devops_user
}

3. Output Paths ​

hcl
output "ssh_connect_cmd" {
  value = module.ssh_known_hosts.ssh_wrapper_path
}

Verification ​

bash
terraform apply
ls bin/  # See wrapper script
./bin/ssh  # Works!

Problems & Learnings ​

Common Issues

  • cat gen/known_hosts fails inside the SSH session — gen/known_hosts is generated locally by Terraform on your machine. Exit the server and check it locally in the exercise directory.

Key Takeaways

  • The SshKnownHosts module encapsulates all SSH wrapper logic — the calling exercise only needs to pass server_ip and devops_username
  • Generated files (bin/ssh, bin/scp, gen/known_hosts) are always local to your machine, never on the remote server