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blog/content/posts/2022-05-09-installing-nixos-on-encrypted-zfs.md

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+++ title = "Installing NixOS on ZFS with encryption" date = 2022-05-09 tags = ["nixos", "linux", "setup"] toc = true +++

I finally switched over to NixOS for my desktop, and here is my install process.

Annoyingly enough, the biggest non-declarative part of Nix is this

initial setup phase, and I made several mistakes during the install process, so I'm documenting the process here so I can remember for next time.

  • CPU: AMD Ryzen 7 3700X
  • GPU: NVIDIA GeForce RTX 3080 Ti
  • RAM: 80GB
  • Storage:
    • SSD1: 1TB Samsung SSD 860 (encrypted), which I'm migrating off of
    • SSD2: 2TB Crucial MX500 (encrypted), which I'm migrating to
    • HDD: 3TB HITACHI HUA72303 (unencrypted), which serves as storage for music and games.

I already have my Nix flake setup for my other machines, but of those only my server runs NixOS. Instead, all my other machines use Arch Linux with just the Nix package manager installed on top.

Installation Media

Since I'm using two SSDs, I don't bother with flashing the installation media on a USB stick and rebooting into that. I can just use Nix to get the tools that I need:

nix shell nixpkgs#nixos-install-tools

This will get me scripts like nixos-generate-config and nixos-install which I'll need for my setup.

Disk Setup

First, I identified my disks. This can be done using ls -l /dev/disk/by-id and identifying the one corresponding to your disk.

export SSD1=/dev/disk/by-id/ata-Samsung_SSD_860_EVO_1TB_[...]
export SSD2=/dev/disk/by-id/ata-CT2000MX500SSD1_[...]
export HDD=/dev/disk/by-id/ata-HITACHI_HUA723030ALA640_[...]

Then, using some of the other references out there, I carefully used sgdisk to construct the partition tables. I want to dual boot NixOS with Windows, so I'm purposefully leaving out around 40% of the disk for that partition. (Note: use sgdisk -L to get the IDs for the -t parameter)

# Zap the disk
sgdisk --zap $SSD2

# 1: Boot partition
sgdisk -n1:1M:+512M -t1:ef00 $SSD2

# 2: NixOS partition
# Note: bf01 is "Solaris /usr & Mac ZFS"
sgdisk -n2:0:+1000G -t2:bf01 $SSD2

We'll let Windows create its own partitions using its installer later.

ZFS Setup

zpool create \
  -o ashift=12              `# 2^12 = 4096 sector size, note small o` \
  -o autotrim=on \
  -O acltype=posixacl       `# needed for some things` \
  -O atime=off              `# turn off access time` \
  -O mountpoint=none        `# turn off automatic mounting` \
  -O compression=lz4        `# sure, why not` \
  -O xattr=sa \
  -O encryption=aes-256-gcm `# disk encryption` \
  -O keyformat=passphrase \
  rpool $SSD2-part2

It'll prompt for the encryption passphrase now.

mkfs.vfat $SSD2-part1
zfs create -o mountpoint=legacy rpool/nixos

Mount them:

export MNT=/mnt/nixos
mount -t zfs rpool/nixos $MNT

mkdir $MNT/boot
mount $SSD2-part1 $MNT/boot

NixOS Hardware Configuration

nixos-generate-config --root $MNT

This writes the default configuration along with the results of the hardware scan. Although it says not to edit the file, this scrapes all of my virtual network interfaces which I do not want in my general config, so I'll trim it a bit. Edit the file with:

$EDITOR $MNT/etc/nixos/hardware-configuration.nix

For the configuration.nix file, the following needs to be added somewhere in the file in order to get ZFS to work:

{
  boot.supportedFilesystems = [ "zfs" ];
  networking.hostId = "<8 random hex digits>";

}

Also I chose to use GRUB instead of systemd-boot, so replace the line enabling systemd-boot with:

{
  boot.loader.grub.enable = true;
  boot.loader.grub.efiSupport = true;
  boot.loader.grub.device = "nodev";
}

Install NixOS

At this point I copied this configuration into my flake, so I can use all the packages that I've previously set up, including home manager.

Run

nixos-install --root $MNT --flake flake#attr

Done! Now unmount the file systems:

umount $MNT/boot
umount $MNT

References