290 lines
12 KiB
Bash
290 lines
12 KiB
Bash
#!/usr/bin/env bash
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# Installs NixOS on a Hetzner server, wiping the server.
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#
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# This is for a specific server configuration; adjust where needed.
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#
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# Prerequisites:
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# * Update the script wherever FIXME is present
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#
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# Usage:
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# ssh root@YOUR_SERVERS_IP bash -s < hetzner-dedicated-wipe-and-install-nixos.sh
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#
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# When the script is done, make sure to boot the server from HD, not rescue mode again.
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# Explanations:
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#
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# * Adapted from https://gist.github.com/nh2/78d1c65e33806e7728622dbe748c2b6a
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# * Following largely https://nixos.org/nixos/manual/index.html#sec-installing-from-other-distro.
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# * **Important:** We boot in legacy-BIOS mode, not UEFI, because that's what Hetzner uses.
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# * NVMe devices aren't supported for booting (those require EFI boot)
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# * We set a custom `configuration.nix` so that we can connect to the machine afterwards,
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# inspired by https://nixos.wiki/wiki/Install_NixOS_on_Hetzner_Online
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# * This server has 2 HDDs.
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# We put everything on RAID1.
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# Storage scheme: `partitions -> RAID -> LVM -> ext4`.
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# * A root user with empty password is created, so that you can just login
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# as root and press enter when using the Hetzner spider KVM.
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# Of course that empty-password login isn't exposed to the Internet.
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# Change the password afterwards to avoid anyone with physical access
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# being able to login without any authentication.
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# * The script reboots at the end.
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set -eu
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set -o pipefail
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set -x
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# Inspect existing disks
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lsblk
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# Undo existing setups to allow running the script multiple times to iterate on it.
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# We allow these operations to fail for the case the script runs the first time.
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set +e
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umount /mnt
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vgchange -an
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set -e
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# Stop all mdadm arrays that the boot may have activated.
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mdadm --stop --scan
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# Prevent mdadm from auto-assembling arrays.
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# Otherwise, as soon as we create the partition tables below, it will try to
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# re-assemple a previous RAID if any remaining RAID signatures are present,
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# before we even get the chance to wipe them.
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# From:
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# https://unix.stackexchange.com/questions/166688/prevent-debian-from-auto-assembling-raid-at-boot/504035#504035
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# We use `>` because the file may already contain some detected RAID arrays,
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# which would take precedence over our `<ignore>`.
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echo 'AUTO -all
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ARRAY <ignore> UUID=00000000:00000000:00000000:00000000' > /etc/mdadm/mdadm.conf
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# Create partition tables (--script to not ask)
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parted --script /dev/sda mklabel gpt
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parted --script /dev/sdb mklabel gpt
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# Create partitions (--script to not ask)
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#
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# We create the 1MB BIOS boot partition at the front.
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#
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# Note we use "MB" instead of "MiB" because otherwise `--align optimal` has no effect;
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# as per documentation https://www.gnu.org/software/parted/manual/html_node/unit.html#unit:
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# > Note that as of parted-2.4, when you specify start and/or end values using IEC
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# > binary units like "MiB", "GiB", "TiB", etc., parted treats those values as exact
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#
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# Note: When using `mkpart` on GPT, as per
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# https://www.gnu.org/software/parted/manual/html_node/mkpart.html#mkpart
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# the first argument to `mkpart` is not a `part-type`, but the GPT partition name:
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# ... part-type is one of 'primary', 'extended' or 'logical', and may be specified only with 'msdos' or 'dvh' partition tables.
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# A name must be specified for a 'gpt' partition table.
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# GPT partition names are limited to 36 UTF-16 chars, see https://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_entries_(LBA_2-33).
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parted --script --align optimal /dev/sda -- mklabel gpt mkpart 'BIOS-boot-partition' 1MB 2MB set 1 bios_grub on mkpart 'data-partition' 2MB '100%'
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parted --script --align optimal /dev/sdb -- mklabel gpt mkpart 'BIOS-boot-partition' 1MB 2MB set 1 bios_grub on mkpart 'data-partition' 2MB '100%'
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# Relaod partitions
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partprobe
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# Wait for all devices to exist
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udevadm settle --timeout=5 --exit-if-exists=/dev/sda1
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udevadm settle --timeout=5 --exit-if-exists=/dev/sda2
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udevadm settle --timeout=5 --exit-if-exists=/dev/sdb1
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udevadm settle --timeout=5 --exit-if-exists=/dev/sdb2
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# Wipe any previous RAID signatures
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mdadm --zero-superblock --force /dev/sda2
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mdadm --zero-superblock --force /dev/sdb2
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# Create RAIDs
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# Note that during creating and boot-time assembly, mdadm cares about the
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# host name, and the existence and contents of `mdadm.conf`!
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# This also affects the names appearing in /dev/md/ being different
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# before and after reboot in general (but we take extra care here
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# to pass explicit names, and set HOMEHOST for the rebooting system further
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# down, so that the names appear the same).
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# Almost all details of this are explained in
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# https://bugzilla.redhat.com/show_bug.cgi?id=606481#c14
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# and the followup comments by Doug Ledford.
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mdadm --create --run --verbose /dev/md0 --level=1 --raid-devices=2 --homehost=hetzner --name=root0 /dev/sda2 /dev/sdb2
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# Assembling the RAID can result in auto-activation of previously-existing LVM
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# groups, preventing the RAID block device wiping below with
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# `Device or resource busy`. So disable all VGs first.
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vgchange -an
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# Wipe filesystem signatures that might be on the RAID from some
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# possibly existing older use of the disks (RAID creation does not do that).
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# See https://serverfault.com/questions/911370/why-does-mdadm-zero-superblock-preserve-file-system-information
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wipefs -a /dev/md0
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# Disable RAID recovery. We don't want this to slow down machine provisioning
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# in the rescue mode. It can run in normal operation after reboot.
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echo 0 > /proc/sys/dev/raid/speed_limit_max
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# LVM
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# PVs
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pvcreate /dev/md0
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# VGs
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vgcreate vg0 /dev/md0
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# LVs (--yes to automatically wipe detected file system signatures)
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lvcreate --yes --extents 95%FREE -n root0 vg0 # 5% slack space
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# Filesystems (-F to not ask on preexisting FS)
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mkfs.ext4 -F -L root /dev/mapper/vg0-root0
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# Creating file systems changes their UUIDs.
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# Trigger udev so that the entries in /dev/disk/by-uuid get refreshed.
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# `nixos-generate-config` depends on those being up-to-date.
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# See https://github.com/NixOS/nixpkgs/issues/62444
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udevadm trigger
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# Wait for FS labels to appear
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udevadm settle --timeout=5 --exit-if-exists=/dev/disk/by-label/root
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# NixOS pre-installation mounts
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# Mount target root partition
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mount /dev/disk/by-label/root /mnt
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# Installing nix
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# Installing nix requires `sudo`; the Hetzner rescue mode doesn't have it.
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apt-get install -y sudo
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# Allow installing nix as root, see
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# https://github.com/NixOS/nix/issues/936#issuecomment-475795730
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mkdir -p /etc/nix
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echo "build-users-group =" > /etc/nix/nix.conf
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curl -L https://nixos.org/nix/install | sh
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set +u +x # sourcing this may refer to unset variables that we have no control over
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. $HOME/.nix-profile/etc/profile.d/nix.sh
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set -u -x
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# FIXME Keep in sync with `system.stateVersion` set below!
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nix-channel --add https://nixos.org/channels/nixos-20.03 nixpkgs
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nix-channel --update
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# Getting NixOS installation tools
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nix-env -iE "_: with import <nixpkgs/nixos> { configuration = {}; }; with config.system.build; [ nixos-generate-config nixos-install nixos-enter manual.manpages ]"
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nixos-generate-config --root /mnt
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# Find the name of the network interface that connects us to the Internet.
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# Inspired by https://unix.stackexchange.com/questions/14961/how-to-find-out-which-interface-am-i-using-for-connecting-to-the-internet/302613#302613
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RESCUE_INTERFACE=$(ip route get 8.8.8.8 | grep -Po '(?<=dev )(\S+)')
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# Find what its name will be under NixOS, which uses stable interface names.
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# See https://major.io/2015/08/21/understanding-systemds-predictable-network-device-names/#comment-545626
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# NICs for most Hetzner servers are not onboard, which is why we use
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# `ID_NET_NAME_PATH`otherwise it would be `ID_NET_NAME_ONBOARD`.
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INTERFACE_DEVICE_PATH=$(udevadm info -e | grep -Po "(?<=^P: )(.*${RESCUE_INTERFACE})")
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UDEVADM_PROPERTIES_FOR_INTERFACE=$(udevadm info --query=property "--path=$INTERFACE_DEVICE_PATH")
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NIXOS_INTERFACE=$(echo "$UDEVADM_PROPERTIES_FOR_INTERFACE" | grep -o -E 'ID_NET_NAME_PATH=\w+' | cut -d= -f2)
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echo "Determined NIXOS_INTERFACE as '$NIXOS_INTERFACE'"
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IP_V4=$(ip route get 8.8.8.8 | grep -Po '(?<=src )(\S+)')
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echo "Determined IP_V4 as $IP_V4"
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# Determine Internet IPv6 by checking route, and using ::1
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# (because Hetzner rescue mode uses ::2 by default).
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# The `ip -6 route get` output on Hetzner looks like:
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# # ip -6 route get 2001:4860:4860:0:0:0:0:8888
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# 2001:4860:4860::8888 via fe80::1 dev eth0 src 2a01:4f8:151:62aa::2 metric 1024 pref medium
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IP_V6="$(ip route get 2001:4860:4860:0:0:0:0:8888 | head -1 | cut -d' ' -f7 | cut -d: -f1-4)::1"
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echo "Determined IP_V6 as $IP_V6"
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# From https://stackoverflow.com/questions/1204629/how-do-i-get-the-default-gateway-in-linux-given-the-destination/15973156#15973156
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read _ _ DEFAULT_GATEWAY _ < <(ip route list match 0/0); echo "$DEFAULT_GATEWAY"
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echo "Determined DEFAULT_GATEWAY as $DEFAULT_GATEWAY"
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# Generate `configuration.nix`. Note that we splice in shell variables.
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cat > /mnt/etc/nixos/configuration.nix <<EOF
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{ config, pkgs, ... }:
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{
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imports =
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[ # Include the results of the hardware scan.
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./hardware-configuration.nix
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];
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# Use GRUB2 as the boot loader.
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# We don't use systemd-boot because Hetzner uses BIOS legacy boot.
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boot.loader.systemd-boot.enable = false;
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boot.loader.grub = {
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enable = true;
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efiSupport = false;
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devices = [ "/dev/sda" "/dev/sdb" ];
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};
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# FIXME
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networking.hostName = "hetzner";
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# The mdadm RAID1s were created with 'mdadm --create ... --homehost=hetzner',
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# but the hostname for each machine may be different, and mdadm's HOMEHOST
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# setting defaults to '<system>' (using the system hostname).
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# This results mdadm considering such disks as "foreign" as opposed to
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# "local", and showing them as e.g. '/dev/md/hetzner:root0'
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# instead of '/dev/md/root0'.
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# This is mdadm's protection against accidentally putting a RAID disk
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# into the wrong machine and corrupting data by accidental sync, see
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# https://bugzilla.redhat.com/show_bug.cgi?id=606481#c14 and onward.
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# We set the HOMEHOST manually go get the short '/dev/md' names,
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# and so that things look and are configured the same on all such
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# machines irrespective of host names.
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# We do not worry about plugging disks into the wrong machine because
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# we will never exchange disks between machines.
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environment.etc."mdadm.conf".text = ''
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HOMEHOST hetzner
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'';
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# The RAIDs are assembled in stage1, so we need to make the config
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# available there.
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boot.initrd.mdadmConf = config.environment.etc."mdadm.conf".text;
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# Network (Hetzner uses static IP assignments, and we don't use DHCP here)
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networking.useDHCP = false;
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networking.interfaces."$NIXOS_INTERFACE".ipv4.addresses = [
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{
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address = "$IP_V4";
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prefixLength = 24;
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}
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];
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networking.interfaces."$NIXOS_INTERFACE".ipv6.addresses = [
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{
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address = "$IP_V6";
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prefixLength = 64;
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}
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];
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networking.defaultGateway = "$DEFAULT_GATEWAY";
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networking.defaultGateway6 = { address = "fe80::1"; interface = "$NIXOS_INTERFACE"; };
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networking.nameservers = [ "8.8.8.8" ];
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# Initial empty root password for easy login:
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users.users.root.initialHashedPassword = "";
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services.openssh.permitRootLogin = "prohibit-password";
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users.users.root.openssh.authorizedKeys.keys = [
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# FIXME Replace this by your SSH pubkey!
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"ssh-rsa AAAAAAAAAAA..."
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];
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services.openssh.enable = true;
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# FIXME
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# This value determines the NixOS release with which your system is to be
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# compatible, in order to avoid breaking some software such as database
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# servers. You should change this only after NixOS release notes say you
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# should.
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system.stateVersion = "20.03"; # Did you read the comment?
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}
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EOF
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# Install NixOS
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PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --no-root-passwd --root /mnt --max-jobs 40
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umount /mnt
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reboot
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