Installation of NixOS with encrypted root

These are my notes on instaling NixOS 16.03 on a Lenovo ThinkPad X1 Carbon (4th generation) with an encrypted root file system using UEFI.

Most of this is scrambled from the following pages:

Preparing installation media

I installed from a USB stick using the NixOS minimal ISO (this one to be precise).

$ dd bs=4M if=nixos-minimal-16.03.678.2597f52-x86_64-linux.iso of=/dev/sdb

Booting the installer

Disable Secure Boot Control
Disable USB legacy boot
Enable Launch CSM

Due to this kernel bug, we have to boot with the following kernel parameter: intel_pstate=no_hwp. Seems like this will be fixed soon.

Partitioning

We create a 500MB EFI boot partition (/dev/sda1) and the rest will be our LUKS encrypted physical volume for LVM (/dev/sda2).

$ gdisk /dev/sda

o (create new empty partition table)
n (add partition, 500M, type ef00 EFI)
n (add partition, remaining space, type 8e00 Linux LVM)
w (write partition table and exit)

Setup the encrypted LUKS partition and open it:

$ cryptsetup luksFormat /dev/sda2
$ cryptsetup luksOpen /dev/sda2 enc-pv

We create two logical volumes, a 8GB swap parition and the rest will be our root filesystem

$ pvcreate /dev/mapper/enc-pv
$ vgcreate vg /dev/mapper/enc-pv
$ lvcreate -L 8G -n swap vg
$ lvcreate -l '100%FREE' -n root vg

Format the partitions:

$ mkfs.fat /dev/sda1
$ mkfs.ext4 -L root /dev/vg/root
$ mkswap -L swap /dev/vg/swap

Installing NixOS

We mount the partitions we just created under /mnt so we can install NixOS on them.

$ mount /dev/vg/root /mnt
$ mkdir /mnt/boot
$ mount /dev/sda1 /mnt/boot
$ swapon /dev/vg/swap

Configure WPA supplicant so we can use WIFI:

$ cat > /etc/wpa_supplicant.conf
network={
  ssid="****"
  psk="****"
}
^D
$ systemctl start wpa_supplicant

Now generate a NixOS configuration and modify it to our liking. The following is the configuration I started with.

$ nixos-generate-config --root /mnt
$ cat > /mnt/etc/nixos/configuration.nix
{ config, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # https://bugzilla.kernel.org/show_bug.cgi?id=110941
  boot.kernelParams = [ "intel_pstate=no_hwp" ];

  # Supposedly better for the SSD.
  fileSystems."/".options = [ "noatime" "nodiratime" "discard" ];

  # Use the GRUB 2 boot loader.
  boot.loader.grub.enable = true;
  boot.loader.grub.version = 2;
  boot.loader.grub.device = "nodev";
  boot.loader.grub.efiSupport = true;
  boot.loader.efi.canTouchEfiVariables = true;

  # Grub menu is painted really slowly on HiDPI, so we lower the
  # resolution. Unfortunately, scaling to 1280x720 (keeping aspect
  # ratio) doesn't seem to work, so we just pick another low one.
  boot.loader.grub.gfxmodeEfi = "1024x768";

  boot.initrd.luks.devices = [
    {
      name = "root";
      device = "/dev/disk/by-uuid/06e7d974-9549-4be1-8ef2-f013efad727e";
      preLVM = true;
      allowDiscards = true;
    }
  ];

  # Enables wireless support via wpa_supplicant.
  networking.wireless.enable = true;

  # Etcetera ...
}

If we're happy with the configuration, install NixOS and reboot.

$ nixos-install
$ reboot

Troubleshooting

If for whatever reason the system doesn't boot, we can go back to the installation environment by booting from the installation media and remounting all partitions:

$ cryptsetup luksOpen /dev/sda2 enc-pv
$ lvchange -a y /dev/vg/swap
$ lvchange -a y /dev/vg/root
$ mount /dev/vg/root /mnt
$ mount /dev/sda1 /mnt/boot
$ swapon /dev/vg/swap
$ cp /mnt/etc/wpa_supplicant.conf /etc
$ systemctl start wpa_supplicant

We can now make further modifications to the configuration and try again.