#!/usr/bin/env bash

# Installs NixOS on a Hetzner server, wiping the server.
#
# This is for a specific server configuration; adjust where needed.
#
# Prerequisites:
#   * Update the script wherever FIXME is present
#
# Usage:
#     ssh root@YOUR_SERVERS_IP bash -s < hetzner-dedicated-wipe-and-install-nixos.sh
#
# When the script is done, make sure to boot the server from HD, not rescue mode again.

# Explanations:
#
# * Adapted from https://gist.github.com/nh2/78d1c65e33806e7728622dbe748c2b6a
# * Following largely https://nixos.org/nixos/manual/index.html#sec-installing-from-other-distro.
# * **Important:** We boot in legacy-BIOS mode, not UEFI, because that's what Hetzner uses.
#   * NVMe devices aren't supported for booting (those require EFI boot)
# * We set a custom `configuration.nix` so that we can connect to the machine afterwards,
#   inspired by https://nixos.wiki/wiki/Install_NixOS_on_Hetzner_Online
# * This server has 2 HDDs.
#   We put everything on RAID1.
#   Storage scheme: `partitions -> RAID -> LVM -> ext4`.
# * A root user with empty password is created, so that you can just login
#   as root and press enter when using the Hetzner spider KVM.
#   Of course that empty-password login isn't exposed to the Internet.
#   Change the password afterwards to avoid anyone with physical access
#   being able to login without any authentication.
# * The script reboots at the end.

# * does not use uefi (check if you can : efibootmgr)
# Notes https://mazzo.li/posts/hetzner-zfs.html

# FIXME : change password
MAIN_PASSWORD="KlEBgwLgksT71cfIixM3eNDjIaZgFFvMDY8EoBs1Il"

set -eu
set -o pipefail

set -x

# Inspect existing disks
lsblk

# Undo existing setups to allow running the script multiple times to iterate on it.
# We allow these operations to fail for the case the script runs the first time.
set +e
umount /mnt/boot-{1,2}
umount /mnt
vgchange -an
cryptsetup close a_encrypted
cryptsetup close b_encrypted
set -e


# Stop all mdadm arrays that the boot may have activated.
mdadm --stop --scan

# Prevent mdadm from auto-assembling arrays.
# Otherwise, as soon as we create the partition tables below, it will try to
# re-assemple a previous RAID if any remaining RAID signatures are present,
# before we even get the chance to wipe them.
# From:
#     https://unix.stackexchange.com/questions/166688/prevent-debian-from-auto-assembling-raid-at-boot/504035#504035
# We use `>` because the file may already contain some detected RAID arrays,
# which would take precedence over our `<ignore>`.
echo 'AUTO -all
ARRAY <ignore> UUID=00000000:00000000:00000000:00000000' > /etc/mdadm/mdadm.conf

# Create partition tables (--script to not ask)
#parted --script /dev/sda mklabel gpt
#parted --script /dev/sdb mklabel gpt

#parted /dev/sda -- mklabel gpt
#parted /dev/sda -- mkpart ESP fat32 1MiB 512MiB
#parted /dev/sda -- set 1 boot on
#parted /dev/sda -- mkpart primary 512MiB 100%

format() {
  parted -s "$1" -- mklabel gpt

  parted -s "$1" -- mkpart 'BIOS-boot-partition' 1MB 2MB set 1 bios_grub on
  #parted -s "$1" -- mkpart 'boot' 2MB 512MiB
  #parted -s "$1" -- mkpart ESP fat32 2MB 512MiB
  parted -s "$1" -- mkpart ESP fat32 2MB 512MiB set 2 boot on

  #parted -s "$1" -- mkpart ESP fat32 1MiB 512MiB

  parted -s "$1" -- mkpart primary 512MiB 100%
  parted -s "$1" -- print
}

# In this particular machine we have two NVMe disks
format /dev/sda
format /dev/sdb


# Create partitions (--script to not ask)
#
# We create the 1MB BIOS boot partition at the front.
#
# Note we use "MB" instead of "MiB" because otherwise `--align optimal` has no effect;
# as per documentation https://www.gnu.org/software/parted/manual/html_node/unit.html#unit:
# > Note that as of parted-2.4, when you specify start and/or end values using IEC
# > binary units like "MiB", "GiB", "TiB", etc., parted treats those values as exact
#
# Note: When using `mkpart` on GPT, as per
#   https://www.gnu.org/software/parted/manual/html_node/mkpart.html#mkpart
# the first argument to `mkpart` is not a `part-type`, but the GPT partition name:
#   ... part-type is one of 'primary', 'extended' or 'logical', and may be specified only with 'msdos' or 'dvh' partition tables.
#   A name must be specified for a 'gpt' partition table.
# GPT partition names are limited to 36 UTF-16 chars, see https://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_entries_(LBA_2-33).
#parted --script --align optimal /dev/sda -- mklabel gpt mkpart 'BIOS-boot-partition' 1MB 2MB set 1 bios_grub on mkpart 'data-partition' 2MB '100%'
#parted --script --align optimal /dev/sdb -- mklabel gpt mkpart 'BIOS-boot-partition' 1MB 2MB set 1 bios_grub on mkpart 'data-partition' 2MB '100%'

# Relaod partitions
#partprobe

# Wait for all devices to exist
udevadm settle --timeout=5 --exit-if-exists=/dev/sda1
udevadm settle --timeout=5 --exit-if-exists=/dev/sda2
udevadm settle --timeout=5 --exit-if-exists=/dev/sda3
udevadm settle --timeout=5 --exit-if-exists=/dev/sdb1
udevadm settle --timeout=5 --exit-if-exists=/dev/sdb2
udevadm settle --timeout=5 --exit-if-exists=/dev/sdb3

# Wipe any previous RAID signatures
#mdadm --zero-superblock --force /dev/sda2
#mdadm --zero-superblock --force /dev/sdb2

# Create RAIDs
# Note that during creating and boot-time assembly, mdadm cares about the
# host name, and the existence and contents of `mdadm.conf`!
# This also affects the names appearing in /dev/md/ being different
# before and after reboot in general (but we take extra care here
# to pass explicit names, and set HOMEHOST for the rebooting system further
# down, so that the names appear the same).
# Almost all details of this are explained in
#   https://bugzilla.redhat.com/show_bug.cgi?id=606481#c14
# and the followup comments by Doug Ledford.
#mdadm --create --run --verbose /dev/md0 --level=1 --raid-devices=2 --homehost=hetzner --name=root0 /dev/sda2 /dev/sdb2

# Assembling the RAID can result in auto-activation of previously-existing LVM
# groups, preventing the RAID block device wiping below with
# `Device or resource busy`. So disable all VGs first.
#vgchange -an

# Wipe filesystem signatures that might be on the RAID from some
# possibly existing older use of the disks (RAID creation does not do that).
# See https://serverfault.com/questions/911370/why-does-mdadm-zero-superblock-preserve-file-system-information
#wipefs -a /dev/md0

# Disable RAID recovery. We don't want this to slow down machine provisioning
# in the rescue mode. It can run in normal operation after reboot.
echo 0 > /proc/sys/dev/raid/speed_limit_max

# LVM

encrypt() {
  device=$1
  label=$2
  echo $MAIN_PASSWORD | cryptsetup luksFormat ${device}3 -
  echo $MAIN_PASSWORD | cryptsetup --key-file - open --type luks ${device}3 ${label}_encrypted
}

encrypt /dev/sda "a"
encrypt /dev/sdb "b"



# PVs
#pvcreate /dev/md0

pvcreate /dev/mapper/a_encrypted
pvcreate /dev/mapper/b_encrypted

# VGs
vgcreate vg /dev/mapper/a_encrypted /dev/mapper/b_encrypted
#vgcreate vg0 /dev/md0
# LVs (--yes to automatically wipe detected file system signatures)

# the root partition should be raid1
#lvcreate --mirrors 1 --type raid1 -L 150G --nosync -n root vg
lvcreate --mirrors 1 --type raid1 -L 150G -n root vg

# Filesystems (-F to not ask on preexisting FS)
mkfs.ext4 -F -L root /dev/mapper/vg-root

#mkfs.ext4 -F -L boot /dev/sda2
mkfs.fat -F 32 -n boot /dev/sda2
#mkfs.vfat -n boot /dev/sda2

#mkfs.ext4 -F -L boot /dev/sdb2
mkfs.fat -F 32 -n boot /dev/sdb2
#mkfs.vfat -n boot /dev/sdb2

# Creating file systems changes their UUIDs.
# Trigger udev so that the entries in /dev/disk/by-uuid get refreshed.
# `nixos-generate-config` depends on those being up-to-date.
# See https://github.com/NixOS/nixpkgs/issues/62444
udevadm trigger

# Wait for FS labels to appear
udevadm settle --timeout=5 --exit-if-exists=/dev/disk/by-label/root

# NixOS pre-installation mounts

# Mount target root partition
mount /dev/disk/by-label/root /mnt
mkdir -p /mnt/boot-{1,2}
modprobe vfat
mount /dev/sda2 /mnt/boot-1
mount /dev/sdb2 /mnt/boot-2

# Installing nix

# Installing nix requires `sudo`; the Hetzner rescue mode doesn't have it.
apt-get install -y sudo

# Allow installing nix as root, see
#   https://github.com/NixOS/nix/issues/936#issuecomment-475795730
mkdir -p /etc/nix
echo "build-users-group =" > /etc/nix/nix.conf

curl -L https://nixos.org/nix/install | sh
set +u +x # sourcing this may refer to unset variables that we have no control over
. $HOME/.nix-profile/etc/profile.d/nix.sh
set -u -x

# FIXME Keep in sync with `system.stateVersion` set below!
nix-channel --add https://nixos.org/channels/nixos-21.05 nixpkgs
nix-channel --update

# Getting NixOS installation tools
nix-env -iE "_: with import <nixpkgs/nixos> { configuration = {}; }; with config.system.build; [ nixos-generate-config nixos-install nixos-enter manual.manpages ]"

nixos-generate-config --root /mnt

# Find the name of the network interface that connects us to the Internet.
# Inspired by https://unix.stackexchange.com/questions/14961/how-to-find-out-which-interface-am-i-using-for-connecting-to-the-internet/302613#302613
RESCUE_INTERFACE=$(ip route get 8.8.8.8 | grep -Po '(?<=dev )(\S+)')

# Find what its name will be under NixOS, which uses stable interface names.
# See https://major.io/2015/08/21/understanding-systemds-predictable-network-device-names/#comment-545626
# NICs for most Hetzner servers are not onboard, which is why we use
# `ID_NET_NAME_PATH`otherwise it would be `ID_NET_NAME_ONBOARD`.
INTERFACE_DEVICE_PATH=$(udevadm info -e | grep -Po "(?<=^P: )(.*${RESCUE_INTERFACE})")
UDEVADM_PROPERTIES_FOR_INTERFACE=$(udevadm info --query=property "--path=$INTERFACE_DEVICE_PATH")
NIXOS_INTERFACE=$(echo "$UDEVADM_PROPERTIES_FOR_INTERFACE" | grep -o -E 'ID_NET_NAME_PATH=\w+' | cut -d= -f2)
echo "Determined NIXOS_INTERFACE as '$NIXOS_INTERFACE'"
#NIXOS_INTERFACE='eth0'

IP_V4=$(ip route get 8.8.8.8 | grep -Po '(?<=src )(\S+)')
echo "Determined IP_V4 as $IP_V4"

# Determine Internet IPv6 by checking route, and using ::1
# (because Hetzner rescue mode uses ::2 by default).
# The `ip -6 route get` output on Hetzner looks like:
#   # ip -6 route get 2001:4860:4860:0:0:0:0:8888
#   2001:4860:4860::8888 via fe80::1 dev eth0 src 2a01:4f8:151:62aa::2 metric 1024  pref medium
IP_V6="$(ip route get 2001:4860:4860:0:0:0:0:8888 | head -1 | cut -d' ' -f7 | cut -d: -f1-4)::1"
echo "Determined IP_V6 as $IP_V6"


# From https://stackoverflow.com/questions/1204629/how-do-i-get-the-default-gateway-in-linux-given-the-destination/15973156#15973156
read _ _ DEFAULT_GATEWAY _ < <(ip route list match 0/0); echo "$DEFAULT_GATEWAY"
echo "Determined DEFAULT_GATEWAY as $DEFAULT_GATEWAY"


# Generate `configuration.nix`. Note that we splice in shell variables.
cat > /mnt/etc/nixos/configuration.nix <<EOF
{ config, pkgs, modulesPath, lib, ... }:
let
  hostName = "hetzner";
  #  in rescue
  # apt install -y lshw
  # lshw -C network | grep -Poh 'driver=[[:alnum:]]+'
  networkInterfaceModule = "r8169";
  networkInterface = "$NIXOS_INTERFACE";
  # From the Hetzner control panel
  ipv4 = {
    address = "$IP_V4";           # the ip address
    gateway = "$DEFAULT_GATEWAY"; # the gateway ip address
    netmask = "255.255.255.224";  # the netmask -- might not be the same for you!
    prefixLength = 27;            # must match the netmask, see <https://www.pawprint.net/designresources/netmask-converter.php>
  };
  ipv6 = {
    address = "$IP_V6";  # the ipv6 addres
    gateway = "fe80::1"; # the ipv6 gateway
    prefixLength = 64;   # shown in the control panel
  };

in
{
  imports =
    [ # Include the results of the hardware scan.
      # ./hardware-configuration.nix

      #  hardware-configuration content
      {
  imports =
    [ (modulesPath + "/installer/scan/not-detected.nix")
    ];

  boot.initrd.availableKernelModules = [ "ahci" "sd_mod" ];
  boot.initrd.kernelModules = [ "dm-snapshot" ];
  boot.kernelModules = [ "kvm-intel" ];
  boot.extraModulePackages = [ ];

  swapDevices = [ ];
  powerManagement.cpuFreqGovernor = lib.mkDefault "ondemand";

      }
    ];

  # Use GRUB2 as the boot loader.
  # We don't use systemd-boot because Hetzner uses BIOS legacy boot.
  boot.loader.systemd-boot.enable = false;
  boot.loader.grub = {
    enable = true;
    efiSupport = false;
    version = 2;
  };

  # This will mirror all UEFI files, kernels, grub menus and
  # things needed to boot to the other drive.
  boot.loader.grub.mirroredBoots = [
    { path = "/boot-1"; devices = [ "/dev/sda" ]; }
    { path = "/boot-2"; devices = [ "/dev/sdb" ]; }
  ];

  # add later
  # fileSystems."/boot-1".options = [ "nofail" ];
  # fileSystems."/boot-2".options = [ "nofail" ];

  boot.initrd.luks.devices = {
    a_encrypted = {
      device = "/dev/sda3";
      preLVM = true;
    };
    b_encrypted = {
      device = "/dev/sdb3";
      preLVM = true;
    };
  };

  # root
  # ----
  fileSystems."/" = {
    options = [ "noatime" "nodiratime" "discard" ];
    device = "/dev/vg/root";
    fsType = "ext4";
  };

  networking.hostName = hostName;

  # Network configuration (Hetzner uses static IP assignments, and we don't use DHCP here)
  networking.useDHCP = false;
  networking.interfaces.\${networkInterface} = {
    ipv4 = { addresses = [{ address = ipv4.address; prefixLength = ipv4.prefixLength; }]; };
    ipv6 = { addresses = [{ address = ipv6.address; prefixLength = ipv6.prefixLength; }]; };
  };
  networking.defaultGateway = ipv4.gateway;
  networking.defaultGateway6 = { address = ipv6.gateway; interface = networkInterface; };
  networking.nameservers = [ "8.8.8.8" ];

  # Initial empty root password for easy login:
  users.users.root.initialHashedPassword = "";
  services.openssh.permitRootLogin = "prohibit-password";

  users.users.root.openssh.authorizedKeys.keys = [
    # FIXME : add ssh key
    "ssh-rsa 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"
  ];

  services.openssh.enable = true;

  system.stateVersion = "21.05";

  # enable ssh on init
  # ------------------
  boot.kernelParams = [
    # See <https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt> for docs on this
    # ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:<dns0-ip>:<dns1-ip>:<ntp0-ip>
    # The server ip refers to the NFS server -- we don't need it.
    "ip=\${ipv4.address}::\${ipv4.gateway}:\${ipv4.netmask}:\${hostName}-initrd:\${networkInterface}:off:8.8.8.8"
  ];
  boot.initrd.availableKernelModules = [ networkInterfaceModule ];
  boot.initrd.network.enable = true;
  boot.initrd.network.ssh = {
    enable = true;
    authorizedKeys = config.users.users.root.openssh.authorizedKeys.keys;
    port = 22;
    hostKeys = [
    /etc/secrets/initrd/ssh_host_rsa_key
    /etc/secrets/initrd/ssh_host_ed25519_key
    ];

  };


  # make sure ip address is set after in initrd
  #boot.initrd.network.postCommands = ''
  #  up ip addr add $IP_V4/32 dev eth0
  #  #ip address add $IP_V4/32 dev eth0
  #  #ip link set eth0 up
  #  #ip address add $IP_V4/32 dev $NIXOS_INTERFACE
  #  #ip link set eth0 up
  #'';


}
EOF


mkdir -p /mnt/etc/secrets/initrd/

ssh-keygen -t rsa -N "" -f /mnt/etc/secrets/initrd/ssh_host_rsa_key
ssh-keygen -t ed25519 -N "" -f /mnt/etc/secrets/initrd/ssh_host_ed25519_key


# Install NixOS
#PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --no-root-passwd --root /mnt --max-jobs 40
PATH="$PATH" `which nixos-install` --no-root-passwd --root /mnt --max-jobs 40

umount /mnt/boot-{1,2}
umount /mnt

echo "Determined NIXOS_INTERFACE as '$NIXOS_INTERFACE'"
echo "Determined IP_V4 as $IP_V4"
echo "Determined IP_V6 as $IP_V6"
echo "Determined DEFAULT_GATEWAY as $DEFAULT_GATEWAY"
reboot