Cloud provider

Cloud provider
- ➟ Hetzner cloud administration GUI

Sign up at https://accounts.hetzner.com/signUp optionally activating 2-factor authentication. ID card may be required, but no payment
Publish your Hetzner account's username (e.g. the registration e-mail ) to your SDI course's group at https://learn.mi.hdm-stuttgart.de.
Upon confirmation by your lecturer a Hetzner project space e.g. g01 corresponding to your group should be accessible after login.

Your first server

No updates, just (likely) outdated installation image
Password based logins being notoriously prone to attacks.

Solution: Use public/private key based ssh login.
There is no firewall yet restricting network access. Insecurely configured supplementary software components e.g. database servers may lead to disaster.

Two choices:
- Cloud provider level centralized firewall.
- Host local firewall, e.g. Ufw.

sdiuser@martin-pc-dachboden:~$ ssh-keygen -t ed25519 ❶
Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/sdiuser/.ssh/id_ed25519): 
Created directory '/home/sdiuser/.ssh'.
Enter passphrase (empty for no passphrase): ❷
Enter same passphrase again: 
Your identification has been saved in /home/sdiuser/.ssh/id_ed25519 ❸
Your public key has been saved in /home/sdiuser/.ssh/id_ed25519.pub ❹

Improve your server's security!

Caution

This is about $$$ MONEY $$$

Delete your server including the IPv4 address.
You may optionally delete your firewall.

Cloud provider
- ➟ SDI exercises related DNS server

Dedicated lecture related DNS server ns1.sdi.hdm-stuttgart.cloud.
One subdomain per group e.g. g03.sdi.hdm-stuttgart.cloud corresponding to group 3.
Zone edits require a subdomain specific hmac secret key being provided as dnsupdate.sec file in your personal group entry below the SDI course:
```
hmac-sha512:g03.key:I5sDDS3L1BU...
```
Note

The per zone secrets are being created using tsig-keygen. Value appearing here do not reflect production settings.
Edits become globally visible. Mind the TTL setting: A higher value means you'll have to wait longer until updates become visible.

Key file available in your working group below 113475 Software defined Infrastructure.

$ export HMAC=hmac-sha512:g03.key:YXWSeh3l... 
$ dig @ns1.sdi.hdm-stuttgart.cloud -y $HMAC -t AXFR g03.sdi.hdm-stuttgart.cloud 
...
g03.sdi.hdm-stuttgart.cloud. 10 IN      SOA     ns1.g03.sdi.hdm-stuttgart.cloud. goik.hdm-stuttgart.de. 2024051551 10 10 10 10
g03.sdi.hdm-stuttgart.cloud. 10 IN      NS      ns1.g03.sdi.hdm-stuttgart.cloud.
g03.sdi.hdm-stuttgart.cloud. 10 IN      TXT     "Hello Nerds, how are you going? :-)"
ns1.g03.sdi.hdm-stuttgart.cloud. 10 IN  A       195.201.113.223
g03.sdi.hdm-stuttgart.cloud. 10 IN      SOA     ns1.g03.sdi.hdm-stuttgart.cloud. goik.hdm-stuttgart.de. 2024051551 10 10 10 10
...

See AXFR for details.

export HMAC=hmac-sha512:g03.key:YXWSeh3l... 

$ nsupdate -y $HMAC
> server ns1.sdi.hdm-stuttgart.cloud
> update add www.g03.sdi.hdm-stuttgart.cloud 10 A 141.62.75.114 
> send
> quit
$ dig +noall +answer @ns1.sdi.hdm-stuttgart.cloud www.g03.sdi.hdm-stuttgart.cloud
www.g03.sdi.hdm-stuttgart.cloud. 10 IN  A       141.62.75.114
$ dig  +noall +answer @8.8.8.8  www.g03.sdi.hdm-stuttgart.cloud
www.g03.sdi.hdm-stuttgart.cloud. 10 IN  A       141.62.75.114

$ nsupdate -y $HMAC
> server ns1.sdi.hdm-stuttgart.cloud
> update delete www.g03.sdi.hdm-stuttgart.cloud. 10 IN  A       141.62.75.114
> send
> quit
>
$ dig  +noall +answer @8.8.8.8  www.g03.sdi.hdm-stuttgart.cloud
$

Note

Examples at DNS Updates with nsupdate

Enhancing your web server.

Cloud provider
- ➟ Working with Terraform

Quote:

“Terraform is an infrastructure as code tool that lets you build, change, and version cloud and on-prem resources safely and efficiently.”

Access you cloud project using the Hetzner GUI interface.
Go to Security --> API Tokens --> Generate API token
Provide a name and hit Generate API token.
Copy the generated token's value and store it in a secure location e.g. a password manager.

Caution

The Hetzner GUI blocks future access to the token.

# Define Hetzner cloud provider
terraform {
  required_providers {
    hcloud = {
      source = "hetznercloud/hcloud"
    }
  }
  required_version = ">= 0.13"
}

# Configure the Hetzner Cloud API token
provider "hcloud" {
  token = "your_api_token_goes_here"
}

# Create a server
resource "hcloud_server" "helloServer" {
  name         = "hello"
  image        =  "debian-12"
  server_type  =  "cx22"   
}

$ terraform init

Initializing the backend...

Initializing provider plugins...
- Finding latest version of hetznercloud/hcloud...
- Installing hetznercloud/hcloud v1.46.1...
- Installed hetznercloud/hcloud v1.46.1 (signed by a HashiCorp partner, key ID 5219EACB3A77198B)

...
Terraform has created a lock file .terraform.lock.hcl to record the provider
selections it made above.  ...

$ terraform plan

Terraform used the selected providers to generate the following execution plan. Resource actions ...
  + create

Terraform will perform the following actions:

  # hcloud_server.helloServer will be created
  + resource "hcloud_server" "helloServer" {
      + allow_deprecated_images    = false
      + backup_window              = (known after apply)
  ...
    }

Plan: 1 to add, 0 to change, 0 to destroy.

$ terraform apply
...
Plan: 1 to add, 0 to change, 0 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

hcloud_server.helloServer: Creating...
hcloud_server.helloServer: Still creating... [10s elapsed]
hcloud_server.helloServer: Creation complete after 14s [id=45822789]

Apply complete! Resources: 1 added, 0 changed, 0 destroyed.

Guide to Managing Terraform secrets.

`variables.tf`	`env`	`providers.tf`
variable "hcloud_token" { nullable = false sensitive = true }	export TF_VAR_hcloud_token=mBSxD...	provider "hcloud" { token = var.hcloud_token }
`. env # sourcing environment terraform apply`

Your server "hello" was created!

You can access your server with the following credentials:
 
IPv4	128.140.108.60
IPv6	2a01:4f8:1c1c:8e3a::/64
User	root
Password	rJ3pNvJXbqMp3XNTvFdq

You will be prompted to change your password on your first login.

To improve security, we recommend that you add an SSH key when creating a server.

Firewall blocks ssh server access:
```
$ ssh root@128.140.108.60
ssh: connect to host 128.140.108.60 port 22: Connection refused
```
Access by Vnc console login only
IP and (initial) credentials by email 😱

Solution:

Add firewall inbound ssh access rule.
Configure ssh public key login.

resource "hcloud_firewall" "sshFw" {
  name = "ssh-firewall"
  rule {
    direction = "in"
    protocol  = "tcp"
    port      = "22"
    source_ips = ["0.0.0.0/0", "::/0"]
  }
}
              ...
resource "hcloud_server" "helloServer" {
              ...
  firewall_ids = [hcloud_firewall.sshFw.id]
}

resource "hcloud_ssh_key" "loginUser" {
  name       = "goik@hdm-stuttgart.de"
  public_key = file("~/.ssh/id_ed25519.pub")
}
              ...
resource "hcloud_server" "helloServer" {
              ...
  ssh_keys     = [hcloud_ssh_key.loginUser.id]
}

Note: Use the Hetzner Web GUI for removing any conflicting manually installed ssh keys beforehand.

$ terraform apply

  # hcloud_firewall.sshFw will be created
  + resource "hcloud_firewall" "sshFw" {
       ...
  # hcloud_server.helloServer will be created
  + resource "hcloud_server" "helloServer" {
       ...
  # hcloud_ssh_key.goik will be created
  + resource "hcloud_ssh_key" "loginUser" {
       ...
Plan: 3 to add, 0 to change, 0 to destroy.
       ...
Apply complete! Resources: 3 added, 0 changed, 0 destroyed.

See terraform output documentation:

File outputs.tf Result

output "hello_ip_addr" {
  value       = hcloud_server.helloServer.ipv4_address
  description = "The server's IPv4 address"
}

output "hello_datacenter" {
  value       = hcloud_server.helloServer.datacenter
  description = "The server's datacenter"
}

$ terraform output
hello_datacenter = "nbg1-dc3"
hello_ip_addr = "159.69.152.37"

$ terraform output hello_ip_addr
"159.69.152.37"

File outputs.tf terraform output -json

output "hello_ip_addr" {
  value       = hcloud_server.helloServer.ipv4_address
  description = "The server's IPv4 address"
}

output "hello_datacenter" {
  value       = hcloud_server.helloServer.datacenter
  description = "The server's datacenter"
}

{
  "hello_datacenter": {
    "sensitive": false,
    "type": "string",
    "value": "nbg1-dc3"
  },
  "hello_ip_addr": {
    "sensitive": false,
    "type": "string",
    "value": "159.69.152.37"
  }
}

Versioned file main.tf:

...
provider "hcloud" { token = "xdaGfz9LmwO8SWkg ... "}
...

Solution:

Declare a variable hcloud_token in a variables.tf file
Add a non-versioned file secrets.auto.tfvars.
Optional: Provide a versioned secrets.auto.tfvars.template documenting file

Declaring hcloud_token in variables.tf:

variable "hcloud_token" {  # See secret.auto.tfvars
  nullable = false
  sensitive = true
}

Defining hcloud_token's value in secrets.auto.tfvars:

hcloud_token="xdaGfz9LmwO8SWkg ... "

Using hcloud_token in main.tf:

provider "hcloud" { token = var.hcloud_token }

Template file secrets.auto.tfvars.template:

hcloud_token="your_api_token_goes_here"

# Configure the Hetzner Cloud API token
provider "hcloud" {
  token = file("../providertoken.key")
}

Content of file providertoken.key:

xdaGfz9LmwO8SWkg ...

Content of file providertoken.key.template:

your_api_token_goes_here

Incrementally creating a base system

Cloud provider
- ➟ Cloud-init

Distribution image containing pre-installed Cloud Init
Script configurable installation options

Individual CRUD file operations
Supplying ssh user and host keys.
Adding users
...

Installing packages
System Upgrade + reboot
Arbitrary command execution

resource "hcloud_server" "web" {
  name         = var.server_name
       ...
  user_data = file("userData.yml")
}

#cloud-config
packages:
  - nginx
runcmd:
  - systemctl enable nginx
  - rm /var/www/html/*
  - >
    echo "I'm Nginx @ $(dig -4 TXT +short o-o.myaddr.l.google.com @ns1.google.com) 
    created $(date -u)" >> /var/www/html/index.html

resource "local_file" "user_data" {
  content         = templatefile("tpl/userData.yml", {
  loginUser              = "devops"
                      })
  filename        = "gen/userData.yml"
}

resource "hcloud_server" "helloServer" {
  ...
  user_data    = local_file.user_data.content
}

Terraform main.tf Cloud-init tpl/userData.yml Cloud-init gen/userData.yml

...
resource "hcloud_server" "my" {
...
 user_data = templatefile(
        "tpl/userData.yml", {
    loginUser = "devops"
  })
}
...

write_files:
 - content: |
    AllowUsers ${loginUser}
    PasswordAuthentication no
...
users:
 - name: ${loginUser}
   groups: sudo
...

write_files:
 - content: |
    AllowUsers devops
    PasswordAuthentication no
...
users:
 - name: devops
   groups: sudo
...

# cloud-init schema --system --annotate

...
apt:		# E1
-   debconf_selections: openssh-server  openssh-server/password-authentication  boolean
        false openssh-server  openssh-server/permit-root-login        boolean false
...
# Errors: -------------
# E1: [{'debconf_selections': 'openssh-server  ....boolean false'}] is not of type 'object'

# cloud-init schema --config-file /var/lib/cloud/instance/user-data.txt
```
Valid cloud-config: /var/lib/cloud/instance/user-data.txt
```

root@hello:~# journalctl -f
May 06 04:41:20 hello cloud-init[898]: Cloud-init v. 22.4.2 finished at Mon, 06 May 2024 04:41:20 +0000. Datasource DataSourceHetzner.  Up 11.78 seconds
   ...
May 06 04:46:16 hello sshd[927]: Invalid user abc from 43.163.218.130 port 33408
May 06 04:46:17 hello sshd[927]: Received disconnect from 43.163.218.130 port 33408:11: Bye Bye [preauth]
May 06 04:46:17 hello sshd[927]: Disconnected from invalid user abc 43.163.218.130 port 33408 [preauth]
   ...
May 06 04:50:54 hello sshd[930]: fatal: Timeout before authentication for 27.128.243.225 port 59866
   ...
May 06 04:52:45 hello sshd[933]: Invalid user cos from 43.163.218.130 port 59776
   ...
May 06 04:53:04 hello sshd[935]: Invalid user admin from 194.169.175.35 port 51128
May 06 04:53:49 hello sshd[937]: User root from 43.163.218.130 not allowed because not listed in AllowUsers
May 06 04:53:49 hello sshd[937]: Disconnected from invalid user root 43.163.218.130 port 50592 [preauth]

Working on Cloud-init

Problem of repeated terraform apply:

$ ssh root@128.140.108.60
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!

resource "local_file" "known_hosts" {
  content         = "${hcloud_server.helloServer.ipv4_address} ...
                      ... ${tls_private_key.host.public_key_openssh}"
  filename        = "gen/known_hosts"
  file_permission = "644"
}

main.tf tpl/ssh.sh

resource "local_file" "ssh_script" {
  content = templatefile("tpl/ssh.sh", {
    ip=hcloud_server.hello.ipv4_address
  })
  filename        = "bin/ssh"
  file_permission = "700"
  depends_on      = [local_file.known_hosts]
}

#!/usr/bin/env bash

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

ssh -o UserKnownHostsFile= \
  "$GEN_DIR/known_hosts" devops@${ip} "$@"

Solving ~/.ssh/known_hosts quirk

#cloud-config

chpasswd:
  list: |
    root:bingo9wingo
  expire: False

#cloud-config

write_files:
  - content:
        ${base64encode(private_key_pem)}
    encoding: base64
    path:  /etc/nginx/snippets/cert/private.pem

Note

Congrats to paultyng

Cloud provider
- ➟ Volumes

resource "hcloud_server" "helloServer" {
  server_type  =  "cx22"
...
}

resource "hcloud_volume" "volume01" {
  name      = "volume1"
  size      = 10
  server_id = hcloud_server.helloServer.id
  automount = true
  format    = "xfs"
}

df
...
/mnt/HC_Volume_100723816

output "volume_id" {
 value=hcloud_volume.volume01.id
 description = "The volume's id"
}

# ls /dev/disk/by-id/*100723816
/dev/disk/by-id/scsi-0HC_Volume_100723816

terraform apply
...
hello_ip_addr="37.27.22.189"
volume_id="100723816"

Desired /etc/fstab:

/dev/disk/by-id/scsi-0HC_Volume_100723816 
  /volume01 xfs discard,nofail,defaults 0 0

Auto mounting a volume

resource "hcloud_server" "helloServer" {
    ...
  user_data = templatefile("tpl/userData.yml", {
     ...
    volume01Id = hcloud_volume.volume01.id
  })
}
resource "hcloud_volume" "volume01" {
  server_id = hcloud_server.helloServer.id
  ...
}

Problem: Cyclic dependency

helloServer <--> volume01

main.tf userData.yml.tpl

resource "hcloud_volume" "vol01" {
  size = 10  ....
}
resource "hcloud_server" "hello" {
  user_data = templatefile(
    "userData.yml.tpl", {
       # No cycle
       volId=hcloud_volume.vol01.id
  })  ...
}
resource "hcloud_volume_attachment"
  "main" {
  volume_id=hcloud_volume.vol01.id
  server_id=hcloud_server.hello.id
}

echo 
 `/bin/ls /dev/disk/by-id/*${volId}` 
 /vol01 xfs discard,nofail,defaults 0 0
  >> /etc/fstab

Mount point's name specification

Cloud provider
- ➟ Private networks

resource "hcloud_network" "pNet" {
  name     = "Private network"
  ip_range = "10.0.0.0/8"
}
resource "hcloud_network_subnet" "pSubnet" {
  network_id   = hcloud_network.pNet.id
  type         = "cloud"
  network_zone = "eu-central"
  ip_range     = "10.0.1.0/24"
}
resource "hcloud_network_route" "gateway"{
  network_id = hcloud_network.pNet.id
  destination = "0.0.0.0/0"
  gateway = "10.0.1.20"
}

resource "hcloud_server" "web" {
    ....
  network {
    network_id = hcloud_network.pNet.id
    ip         = "10.0.1.20"
  }
}

resource "hcloud_server" "web" {
    ....
  public_net {
    ipv4_enabled = false
    ipv6_enabled = false
  }
  network {
    network_id = hcloud_network.pNet.id
    ip         = "10.0.1.20"
  }
}

Creating a subnet

Host “intern” does not have Internet access.
Consequences:
1. No package updates.
2. No package installs
3. ...

- Allow IP forwarding on gateway host
- Configure NAT enabling gateway host as router
Use an application level gateway:
1. apt-cacher-ng
2. Squid

Problem: apt-cacher-ng installation requires time for service to become available.
Consequence: Package installs on host “intern” must be deferred.
Problem: No standard Terraform “service ready” dependency management hook.

#!/bin/bash
echo "Waiting for apt-cacher-ng to launch on port 3142 ..."

while ! nc -z ${frontendPrivatenetIp} 3142; 

  do
     sleep 8 # wait for 8 second before polling again
     echo apt-cacher-ng not yet ready ...
  done

echo "apt-cacher-ng service ready"

resource "null_resource" "waitForProxy" {
  connection {
    type     = "ssh"
    user     = "devops"
    host_key = ...public_key_openssh
    agent    = "true"
    host     = ...web.ipv4_address
  }
  provisioner "remote-exec" {
    inline=["/usr/bin/waitForAptProxy"]
  }
}

resource "hcloud_server" "intern" {
...
  depends_on = [
    hcloud_network_subnet.pSubnet
   ,null_resource.waitForProxy
  ]
}

Adding an application level gateway

Cloud provider
- ➟ Terraform and DNS

Providing DNS info for sdi.hdm-stuttgart.cloud and sub-zones:
- g01.sdi.hdm-stuttgart.cloud
- g02.sdi.hdm-stuttgart.cloud
- ...
Remote API for per-zone editing

provider "dns" {
  update {
    server        = "ns1.sdi.hdm-stuttgart.cloud"
    key_name      = "goik.key."
    key_algorithm = "hmac-sha512"
    key_secret    = file("../dnsupdatetoken.key")
  }
}

resource "dns_a_record_set" "helloRecord" {
  zone = "${var.dnsSubnetName}." # The dot matters!
  name = hcloud_server.helloServer.name
  addresses = [hcloud_server.helloServer.ipv4_address]
  ttl = 10
}

Creating a host with corresponding DNS entry

Cloud provider
- ➟ Generating web SSL certificates

https://www.youtube.com/watch?v=T4Df5_cojAs

Domain Validated: Fully automated process solely based on DNS / infrastructure challenges.
Organization Validated: Checking organization in question.
Extended Validation: Additional checks i.e. telephone based verification.

provider "acme" {
  server_url = "https://acme-staging-v02.api.letsencrypt.org/directory"
}
resource "tls_private_key" "private_key" { algorithm = "RSA" }
resource "acme_registration" "reg" {
  account_key_pem = tls_private_key.private_key.private_key_pem
  email_address   = "nobody@example.com"
}
resource "acme_certificate" "certificate" {
      ...
  dns_challenge { ... }
}

resource "acme_certificate" "certificate" {
  ...
  dns_challenge {
    provider = "route53"
  }
}

acme DNS provider list:

acme-dns
alidns
...
rfc2136
...
zonomi

dns_challenge {
  provider = "rfc2136"

  config = {
    RFC2136_NAMESERVER     = "ns1.sdi.hdm-stuttgart.cloud"
    RFC2136_TSIG_ALGORITHM = "hmac-sha512"
    RFC2136_TSIG_KEY       = "goik.key."
    RFC2136_TSIG_SECRET    = file("../dnsupdatetoken.key")
  }
}

... updating zone 'goik.sdi.hdm-stuttgart.cloud/IN': 
  deleting rrset at '_acme-challenge.goik.sdi.hdm-stuttgart.cloud' TXT
... updating zone 'goik.sdi.hdm-stuttgart.cloud/IN': 
    adding an RR at '_acme-challenge.goik.sdi.hdm-stuttgart.cloud' TXT 
      "GtJZJZjCZLWoGsQDODCFnY37TmMjRiy8Hw9M1eDGhkQ"
... deleting rrset at ... TXT
... adding an RR ... TXT "eJckWl2F43nsf27bzVOjcrTGp_VFeCj2qTVM5Uodg-4"
... deleting an RR at _acme-challenge.goik.sdi.hdm-stuttgart.cloud TXT
... updating zone ... deleting an RR ... TXT

Cloud provider
- ➟ Terraform modules

main.tf Generated files

resource "tls_private_key" "host" {
  algorithm   = "ED25519"
}
resource "hcloud_ssh_key" "loginUser" {
  name       = "devops"
  public_key = file("~/.ssh/id_ed25519.pub")
}
resource "hcloud_server" "server" {
  name         = "www" ...
}
resource "local_file" "ssh_script" {
  content = templatefile("tpl/ssh.sh", {
    ip             = hcloud_server.helloServer.ipv4_address
    devopsUsername = hcloud_ssh_key.loginUser.name
  })
  filename        = "bin/ssh"
  depends_on      = [local_file.known_hosts]
}

Template file tpl/ssh.sh

gen/known_hosts

94.130.229.221 ssh-ed25519 AAAAC3NzaC1lZDI1N...
www.g03.sdi.hdm-stuttgart.cloud ssh-ed25519 ...

bin/ssh

#!/usr/bin/env bash

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

ssh -o UserKnownHostsFile="$GEN_DIR/known_hosts" \
   devops@www.g03.sdi.hdm-stuttgart.cloud "$@"

main.tf Using a module

resource "local_file" "known_hosts" {
  ...
}

resource "local_file" "ssh_script" {
  ...
}

resource "local_file" "scp_script" {
  ...
}

module "localfiles" {
  source    = "../modules/localfiles"

  ipv4       = hcloud_server.webServer.ipv4_address
  dnsZone    = var.dnsZone
  hostNames  = ["www", "cloud"]
  loginUser  = hcloud_ssh_key.loginUser.name
  hostKey    = tls_private_key.host.public_key_openssh
}

variable "ipv4" {
  description = "The server's IPV4 address e.g. '141.62.1.5'"
  type        = string
}

variable "hostNames" {
  description = "Set of unique local host names e.g. [\"www\", \"cloud\"] "
  type        = list
}
...
resource "local_file" "known_hosts" {...

Switching between parent and child module context by ${path.module}:

resource "local_file" "ssh_script" {
  content = templatefile("${path.module}/tpl/ssh.sh", {
    serverFqdn     = "${var.ostNames}.${var.dnsZone}"
    devopsUsername = var.loginUser
  })
  filename        = "bin/ssh"
  file_permission = "755"
  depends_on      = [local_file.known_hosts]
}

A module for local file generation

Cloud provider
- ➟ Terraform loops

Defining 10 server

10 corresponding A-records

resource "hcloud_server" "server" {
  count     = 10
  name      = "www-${count.index}"
  user_data = local_file.user_data[count.index].content
  ...
}

resource "dns_a_record_set" "dnsRecordSet" {
  count     = 10
  zone      = "g03.sdi.hdm-stuttgart.cloud."
  name      = hcloud_server.server[count.index].name
  addresses = [hcloud_server.server[count.index].ipv4_address]
}

Creating a fixed number of servers

Overview

Create and publish a Hetzner account

Followup exercise

Current server security flaws

Preliminary: Create an ssh key pair

Followup exercise

Cleaning up!

Overview

Subdomain per group

Key file location

Querying DNS by zone transfer

Creating an A record

Modify by delete/create

Followup exercise

Overview

What's it all about?

Terraform resources

Hetzner API token

Minimal Terraform configuration

Terraform init

Terraform plan

Terraform apply

A word on storing secrets

Credentials by E-Mail

Problems: 😟

ssh access, firewall

ssh access, public key

Apply ssh key access

Output data details #1/2

Output data details #2/2

Problem 2: VCS and visible provider API token 😱

Solution by variable

Solution by file

Followup exercise

Overview

Introduction and reference

In a nutshell

Configuration options

Terraform interface to Cloud Init

»hello, world ...« userData.yml file

Using and debugging template files

Template files demo

Validation

Watch out for your enemies!

Followup exercise

Problem: Duplicate known_hosts entry on re-creating server

Solution: Generating known_hosts ...

... and ssh wrapper

Followup exercise

Failsafe console login

Avoiding Yaml parsing issues

Overview

A volume: The easy way

Volume details

Followup exercise

Providing a mount point's name

Solution: Independent resource creation

Followup exercise

Overview

Private subnet overview

Private subnet overview

Private subnet overview

Private subnet overview

Private subnet overview

Terraform subnet creation

Gateway host

intern host

Followup exercise

Lack of internet access

Possible solutions

http proxy apt-cacher-ng

http proxy apt-cacher-ng

Cloud-init problem

Service ready query script

Terraform “service ready” dependency hook

Followup exercise

Overview

Bind server ns1.sdi.hdm-stuttgart.cloud

DNS provider

Defining an “A” record

Creating an `A` record

»hello, world ...« `userData.yml` file

Problem: Duplicate `known_hosts` entry on re-creating server

Solution: Generating `known_hosts` ...

Bind server `ns1.sdi.hdm-stuttgart.cloud`

`dns_challenge` provider

Example: Creating `bin/ssh` and `gen/known_hosts`