parti.sh

#!/usr/bin/env bash

prt:all() {
  prt:part "$@"
  prt:lvm
  prt:fs
  prt:mnt
}

prt:part() {
  local disc
  disc=${1:?Error: need disk device as first arg}
  # Note: partition 1 bios_grub is a hack so we can be compatible
  # ...with legacy bios AND use GPT partition tables.
  parted --align optimal --fix --script "$disc" \
    mklabel gpt \
    mkpart primary 1MB 3MB \
    set 1 bios_grub on \
    mkpart eps fat32 3MB 2GB \
    name 2 boot \
    set 2 boot on \
    mkpart primary 2GB 100% \
    name 3 system \
    set 3 lvm on
}

prt:lvm() {
  pvcreate /dev/disk/by-partlabel/system
  vgcreate storage /dev/disk/by-partlabel/system
  lvcreate -l 100%FREE -n root storage /dev/disk/by-partlabel/system
}

prt:fs() {
  mkfs.fat -F 32 /dev/disk/by-partlabel/boot -n BOOT
  mkfs.btrfs /dev/storage/root -L system -f
  sleep 3; sync || true
  mount -t btrfs /dev/disk/by-label/system /mnt/ -o "$btrfsopts"
  btrfs subvolume create /mnt/nix
  btrfs subvolume create /mnt/nixos
  btrfs subvolume create /mnt/home
  btrfs subvolume create /mnt/log

  btrfs subvolume set-default /mnt/nixos
  umount /mnt/
}

prt:mnt() {
  mount -t btrfs /dev/disk/by-label/system /mnt/ -o "$btrfsopts"
  mkdir -p /mnt/{var/log,nix,home,boot}
  chattr +i /mnt/{var/log,nix,home}
  mount -t btrfs /dev/disk/by-label/system /mnt/var/log -o "subvol=/log"
  mount -t btrfs /dev/disk/by-label/system /mnt/nix -o "subvol=/nix"
  mount -t btrfs /dev/disk/by-label/system /mnt/home -o "subvol=/home"
  mount /dev/disk/by-label/BOOT /mnt/boot
}

btrfsopts='autodefrag,space_cache=v2,clear_cache,compress=zstd' 

if [ "$0" = "${BASH_SOURCE[0]}" ]; then
  set -o errexit -o errtrace -o pipefail -o nounset -o xtrace
  cmd=${1:?Need cmd}; shift
  prt:"$cmd" "$@" 
fi

Corresponding fileSystems NixOS config:

  fileSystems =
    let
      device = "/dev/mapper/storage-root";
      fsType = "btrfs";
      btrfsopts = [ "autodefrag" "noatime" "space_cache=v2" "clear_cache" "compress=zstd" ];
    in
    {
      "/" = {
        inherit device fsType;
        options = [ "subvol=nixos" ] ++ btrfsopts;
      };

      "/var/log" = {
        inherit device fsType;
        options = [ "subvol=log" ] ++ btrfsopts;
      };

      "/nix" = {
        inherit device fsType;
        options = [ "subvol=nix" ] ++ btrfsopts;
      };

      "/home" = {
        inherit device fsType;
        options = [ "subvol=home" ] ++ btrfsopts;
      };

      "/boot" = {
        device = "/dev/disk/by-label/BOOT";
        fsType = "vfat";
        options = [ "fmask=0022" "dmask=0022" ];
      };
    };
 
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;
  boot.supportedFilesystems = [ "btrfs" "reiserfs" "vfat" "f2fs" "xfs" "ntfs" "nfs" "cifs" ];
  hardware.enableAllFirmware = true;