Fri 27 Apr 2018 — Fri 01 Jun 2018

NixOS

I run the NixOS distribution of GNU/Linux on my laptop.

Here are useful notes on it.

Installation

The installation instructions for NixOS are difficult to follow precisely.

To make your USB stick: 

sudo dd if=Downloads/nixos-graphical-18.03.132543.8aa385069f8-x86_64-linux.iso of=/dev/sdb

The partitioning instructions are a bit unhelpful. Try using cgdisk or gparted instead. A lot less likely to go wrong.

Once done, make sure to mount both partitions (this is in the instructions, but easy to miss). 

mount /dev/disk/by-label/nixos /mnt
mkdir -p /mnt/boot
mount /dev/disk/by-label/boot /mnt/boot

Lastly, it's easy to boot into a position where you don't have any networking. Make sure network-manager is enabled in your configuration.nix.

If you get into a pickle, you can always boot back into the installer, remount your partitions, and run the install again. 

nixos-install --root /mnt

Dual Boot with Windows

## If you don't set this, Windows will get the time wrong
time.hardwareClockInLocalTime = true;

boot.loader = {
  systemd-boot.enable = true;
  efi.canTouchEfiVariables = true;
}

Deleting Old Generations

When you do sudo nixos-rebuild switch, an entry gets added to EFI for the new generation.

Additionally, you may get a new version of the Linux kernel.

These get stored inside /boot.

NixOS generations use the same mechanism as Nix profiles. They are stored in /nix/var/nix/profiles/system.

As a consequence, you can operate on them using nix-env some-operation -p /nix/var/nix/profiles/system. 

## List all the NixOS configurations we've made in the past
sudo nix-env --list-generations -p /nix/var/nix/profiles/system

## Delete some old generation
sudo nix-env --delete-generations 10000 -p /nix/var/nix/profiles/system