nixfiles

Some of my .nix files

Installing

Disk Setup

Rough sketch of the expected disk layout with full-disk encryption.

Some changes to the sketch for a more realistic scenario:

Swap partition should be at least as big as the machine's RAM to support hibernate-to-disk. Otherwise, it can be omitted altogether in place of a swapfile.
Boot partition can be made bigger to support an embedded recovery image (4-6 GB).

NOTE: If trying in a VM, make sure to use a SCSI virtual disk (instead of HDA) and UEFI enabled.

# Setup partition layout
# Swap should be >RAM size if you're going to use hibernate
parted /dev/sda -- mklabel gpt
parted /dev/sda -- mkpart ESP fat32 1MB 512MB  # boot
parted /dev/sda -- set 1 boot on
parted /dev/sda -- mkpart primary 512MB -1GB  # root
parted /dev/sda -- mkpart primary linux-swap -1GB 100%  # swap

# Encrypt the partitions
# Swap partition is also encrypted, so our hibernate state is encrypted.
# We use luks1 (instead of luks2) because grub2 only supports luks1 for now.
# Follow: https://github.com/NixOS/nixpkgs/issues/65375 for LUKS2 on Grub
# To convert, see: https://cryptsetup-team.pages.debian.net/cryptsetup/encrypted-boot.html
cryptsetup luksFormat --type luks1 /dev/sda2  # Enter password
cryptsetup luksFormat --type luks1 /dev/sda3  # Enter the same password

# Good time to add a key file, if we want to do that:
#   dd if=/dev/urandom of=cryptroot.key bs=1 count=4096
#   chmod 0400 cryptroot.key
#   cryptsetup luksAddKey /dev/sda2 cryptroot.key
#   cryptsetup luksAddKey /dev/sda3 cryptroot.key

# Open the encrypted partitions
cryptsetup open /dev/sda2 cryptroot
cryptsetup open /dev/sda3 cryptswap

# Format the underlying partitions
mkfs.fat -F 32 -n EFI /dev/sda1  # Unencrypted EFI partition
mkswap /dev/mapper/cryptswap
mkfs.btrfs /dev/mapper/cryptroot
mount -o defaults,noatime,compress=lzo,autodefrag /dev/mapper/cryptroot /mnt

# Create volumes on the btrfs root
btrfs subvolume create /mnt/@rootnix
btrfs subvolume create /mnt/@home

# Remount with new volumes
umount /mnt
mount -o compress=lzo,subvol=@rootnix /dev/mapper/cryptroot /mnt
mkdir -p /mnt/boot /mnt/home
mount -o compress=lzo,subvol=@home /dev/mapper/cryptroot /mnt/home
mkdir /mnt/boot/efi
mount /dev/sda1 /mnt/boot/efi

# Enable swap if you're using nixos-generate-config to auto-detect mounts
swapon /dev/mapper/cryptswap

Resume an existing disk setup:

cryptsetup open /dev/sda2 cryptroot  # Enter password
cryptsetup open /dev/sda3 cryptswap  # Enter password

mount -o compress=lzo,subvol=@rootnix /dev/mapper/cryptroot /mnt
mount -o compress=lzo,subvol=@home /dev/mapper/cryptroot /mnt/home
mount /dev/sda1 /mnt/boot/efi

NixOS Setup from another distro

If you're installing from inside another distro, you can use these instructions: https://nixos.org/nixos/manual/index.html#sec-installing-from-other-distro

In Arch, using the aur/nix package does not work.

If we need to add hardware-specific configuration imports, we'll need nixos-hardware (setup instructions). The nix environment activator only includes the nixpkgs channel in the NIX_PATH by default, so we'll need to add that too.

# Activate the nix environment
. $HOME/.nix-profile/etc/profile.d/nix.sh

# Add the nixos-hardware channel
nix-channel --add https://github.com/NixOS/nixos-hardware/archive/master.tar.gz nixos-hardware
nix-channel --update nixos-hardware

# Add the new channel to our NIX_PATH
export NIX_PATH=${NIX_PATH}:${NIX_PATH//nixpkgs/nixos-hardware}

Some other notes for installing from another distro (doesn't apply for a normal install):

${disk.efi} should be mounted to /mnt/boot/efi (or whatever the root prefix is).

After that, off we go:

sudo groupadd -g 30000 nixbld
sudo useradd -u 30000 -g nixbld -G nixbld nixbld
sudo PATH="$PATH" NIX_PATH="$NIX_PATH" `which nixos-install` --root /mnt

NixOS Setup from scratch (in a VM)

curl -Ls "https://github.com/shazow/nixfiles/archive/master.zip" -o nixfiles.zip
unzip nixfiles.zip

mkdir /mnt/etc
mv nixfiles-master /mnt/etc/nixos

cd /mnt/etc/nixos
echo \"$(mkpasswd -m sha-512)\" > .hashedPassword.nix
chmod 400 .hashedPassword.nix

cat > disk.nix << EOF
{
  cryptroot = "/dev/sda2";
  cryptswap = "/dev/sda3";
  efi = "/dev/sda1";
}
EOF

cp hosts/example.nix configuration.nix
echo "Edit configuration.nix ... Some of the paths are wrong here, need to fix."

nixos-install --root /mnt

References

Big thanks to my friend group of NixOS pioneers who paved through the unknowns, and answered many questions along the way.

@arilotter and https://github.com/arilotter/dotfiles
@attente and https://github.com/attente/dotfiles
Bonus shoutout to @jpf for checking out NixOS long before it was cool

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shazow / nixfiles

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