nix

n.b.: this is a guide for using nix/entering nixos on archlinux

• arch wiki - nix
• install nix

pacman -S nix

• start daemon (allows operations on nix store without sudo/root)

sudo systemctl enable nix-daemon.service
sudo systemctl start  nix-daemon.service

• add self to nix-users

sudo gpasswd -a username nix-users

• don't use channels because not reproducible, so don't do the below

nix-channel --add https://nixos.org/channels/nixpkgs-unstable
nix-channel --update

• enable flakes and new CLI interface by editing ~/.config/nix/nix.conf

experimental-features = nix-command flakes

• nix reference manual - garbage collection

nix-collect-garbage

home-manager

• generate initial home-manager configuration

nix run home-manager/master -- init --switch

• problem with gc:

home-manager switch
nix-store --gc
home-manager switch

• keeps clearing/re-downloading on every switch

• looking at the stores: nixpkgs and home-manager, precisely the inputs to the flake

• solution: use nix-direnv to register flake inputs as gc root

• problem: failed to set locale

• solution: set LOCALE_ARCHIVE to

/nix/store/{hash}-glibc-locales-{version}/lib/locale/locale-archive

installing nixos with kexec

• nixos manual - booting into nixos via kexec
• generate default/automatic configuration (configuration.nix/hardware-configuration.nix)

nixos-generate-config

• (optional) use flake template for configuration.nix

nix flake new /etc/nixos -t github:nix-community/home-manager#nixos

configuration tips

• need to import netboot-minimal.nix

  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
      (modulesPath + "/installer/netboot/netboot-minimal.nix")
    ];

• netboot-minimal.nix disables loading linux-firmware, preventing gpu from working

  # overwrite /installer/netboot/netboot-minimal.nix
  hardware.enableRedistributableFirmware = lib.mkForce true;

• on luks, probably need to manually specify root partition

  boot.initrd.luks.devices.cryptlvm.device =
    "/dev/disk/by-uuid/5d57809c-d0e9-49e9-939e-f5d68392faf4";
  # manually specify because `nixos-generate-config` doesn't pick it up
  fileSystems."/" = {
    device = "/dev/VolumeGroup/root";
    fsType = "ext4";
  };

• enable kernel flag boot.shell_on_fail to debug in case things go wrong

  boot.kernelParams = [ "boot.shell_on_fail" ];

entering the build

• not risking normal build (overwrites bootloader), try kexec to prototype
• arch wiki - kexec

pacman -S kexec-tools

• generate kernel image

nix-build '<nixpkgs/nixos>' \
    -I /nix/store/{hash}-nixpkgs \
    --arg configuration ./configuration.nix \
    --attr config.system.build.kexecTree

• if using flakes, path to nixpkgs can also be -I nixpkgs=flake:nixpkgs

• turn off kernel mode setting

• /etc/default/grub

GRUB_CMDLINE_LINUX_DEFAULT="... quiet loglevel=3 ... nomodeset"

• remove amdgpu kernel module

• /etc/mkinitcpio.conf

MODULES=()

• reload grub/initramfs, reboot, go into vt, run sudo ./result/kexec-boot