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Example script to install NixOS on a Hetzner dedicated server via the Hetzner rescue mode
#!/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 to adjust SSH pubkeys, hostname, NixOS version etc.
#
# Usage:
# ssh root@YOUR_SERVERS_IP "$(< 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.
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
vgchange -an vg0
set -e
# Stop all mdadm arrays that the boot may have activated.
mdadm --stop --scan
# Create partition tables (--script to not ask)
parted --script /dev/sda mklabel gpt
parted --script /dev/sdb mklabel gpt
# 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/sdb1
udevadm settle --timeout=5 --exit-if-exists=/dev/sdb2
# Wipe any previous RAID signatures
mdadm --zero-superblock /dev/sda2
mdadm --zero-superblock /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
# 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
# PVs
pvcreate /dev/md0
# VGs
vgcreate vg0 /dev/md0
# LVs (--yes to automatically wipe detected file system signatures)
lvcreate --yes --extents 95%FREE -n root0 vg0 # 5% slack space
# Filesystems (-F to not ask on preexisting FS)
mkfs.ext4 -F -L root /dev/mapper/vg0-root0
# 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
# Installing nix
# Install 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 https://nixos.org/nix/install | sh
set +u +x # sourcing this may refer to unset variables that we have no control over
. $HOME/.nix-profile/etc/profile.d/nix.sh
set -u -x
nix-channel --add https://nixos.org/channels/nixos-19.03 nixpkgs
nix-channel --update
# Getting NixOS installation tools
nix-env -iE "_: with import <nixpkgs/nixos> { configuration = {}; }; with config.system.build; [ nixos-generate-config nixos-install nixos-enter manual.manpages ]"
nixos-generate-config --root /mnt
# On the Hetzner rescue mode, the default Internet interface is called `eth0`.
# Find what its name will be under NixOS, which uses stable interface names.
# See https://major.io/2015/08/21/understanding-systemds-predictable-network-device-names/#comment-545626
INTERFACE=$(udevadm info -e | grep -A 11 ^P.*eth0 | grep -o -E 'ID_NET_NAME_PATH=\w+' | cut -d= -f2)
echo "Determined INTERFACE as $INTERFACE"
# Determine our Internet IP by checking which route would be taken.
# The `ip route get` output on Hetzner looks like:
# # ip route get 8.8.8.8
# 8.8.8.8 via 1.2.3.161 dev eth0 src 1.2.3.165
# cache
IP_V4=$(ip route get 8.8.8.8 | head -1 | cut -d' ' -f7)
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 $DEFAULT_GATEWAY"
# Generate `configuration.nix`. Note that we splice in shell variables.
cat > /mnt/etc/nixos/configuration.nix <<EOF
{ config, pkgs, ... }:
{
imports =
[ # Include the results of the hardware scan.
./hardware-configuration.nix
];
# Use GRUB2 as the boot loader.
# We don't use systemd-boot because Hetzner uses BIOS legacy boot.
boot.loader.systemd-boot.enable = true;
boot.loader.grub = {
enable = true;
efiSupport = false;
devices = [ "/dev/sda" "/dev/sdb" ];
};
networking.hostName = "hetzner";
# The mdadm RAID1s were created with 'mdadm --create ... --homehost=hetzner',
# but the hostname for each machine may be different, and mdadm's HOMEHOST
# setting defaults to '<system>' (using the system hostname).
# This results mdadm considering such disks as "foreign" as opposed to
# "local", and showing them as e.g. '/dev/md/hetzner:data0'
# instead of '/dev/md/data0'.
# This is mdadm's protection against accidentally putting a RAID disk
# into the wrong machine and corrupting data by accidental sync, see
# https://bugzilla.redhat.com/show_bug.cgi?id=606481#c14 and onward.
# We set the HOMEHOST manually go get the short '/dev/md' names,
# and so that things look and are configured the same on all such
# machines irrespective of host names.
# We do not worry about plugging disks into the wrong machine because
# we will never exchange disks between machines.
environment.etc."mdadm.conf".text = ''
HOMEHOST hetzner
'';
# The RAIDs are assembled in stage1, so we need to make the config
# available there.
boot.initrd.mdadmConf = config.environment.etc."mdadm.conf".text;
# Network (Hetzner uses static IP assignments, and we don't use HDCP here)
networking.useDHCP = false;
networking.interfaces."$INTERFACE".ipv4.addresses = [
{
address = "$IP_V4";
prefixLength = 24;
}
];
networking.interfaces."$INTERFACE".ipv6.addresses = [
{
address = "$IP_V6";
prefixLength = 64;
}
];
networking.defaultGateway = "$DEFAULT_GATEWAY";
networking.defaultGateway6 = { address = "fe80::1"; interface = "$INTERFACE"; };
networking.nameservers = [ "8.8.8.8" ];
# Initial empty root password for easy login:
users.users.root.initialHashedPassword = "";
services.openssh.permitRootLogin = "prohibit-password";
users.users.root.openssh.authorizedKeys.keys = [
"ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAtwCIGPYJlD2eeUtxngmT+4yR7BMlK0F5kzj+84uHsxxsy+PXFrP/tScCpwmuoiEYNv/9WKnPJJfCA9XlIDr6cla1MLpaW6eg672TRYMmKzH6SLlkg+kyDmPxSIJw+KdKfnPYyva+Y/VocACYJo0voabUeLAVgtSKGz/AFzccjfOR0GmFO911zjAaR+jFb9M7t7dveNVKm9KbuBfu3giMgGg3/mKz1TKY8yk2ZOxpT5CllBb+B5BcEf+7IGNvNxr1Z0zz5cFXQ3LyBIZklnC/OaQCnD78BSiyPTkIXcmBFal2TaFwTDvki6PuCRpJy+dU1fDdgWLql97D0SVnjmmomw== nh2@deditus.de"
];
services.openssh.enable = true;
# This value determines the NixOS release with which your system is to be
# compatible, in order to avoid breaking some software such as database
# servers. You should change this only after NixOS release notes say you
# should.
system.stateVersion = "19.03"; # Did you read the comment?
}
EOF
# Install NixOS
PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --no-root-passwd --root /mnt --max-jobs 40
reboot
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