NixOS system configuration

My own NixOS system configuration files.

Edit config.json file to specify device and user.

Installation

We will be cooking impermanent BTRFS NixOS setup here. The core idea is to make four subvolumes on the disk itself - root for /, and nix, persistent and snapshots for /nix, /persistent and /snapshots accordingly. Later on we will be mounting those subvolumes to the folders inside of the root subvolume using our nixos mounts config.

Value of the root subvolume will be overwritten each reboot, while all the other subvolumes, being outside of root, will keep their state. In particular, we're really interested in persistent, which will keep our documents and other important data saved on the disk between reboots, and snapshots which will be used to store root subvolume snapshots to keep track of previously written files. This is needed to being able to restore some sensitive data if it was forgotten to be persisted.

1. Create base partitions

Lookup main storage drive name with the lsblk. Then:

sudo -i

parted /dev/sda -- mklabel gpt
parted /dev/sda -- mkpart ESP fat32 1MB 512MB
parted /dev/sda -- set 1 esp on
parted /dev/sda -- mkpart primary 512MB -16GB
parted /dev/sda -- mkpart swap linux-swap -16GB 100%

2. Format the partitions

Verify partitions names via said lsblk again. Then:

mkfs.fat -F 32 -n boot /dev/sda1
mkfs.btrfs -L nixos /dev/sda2
mkswap -L swap /dev/sda3

3. Mount created partitions

mount /dev/sda2 /mnt
swapon /dev/sda3

4. Create btrfs subvolumes

btrfs subvolume create /mnt/root
btrfs subvolume create /mnt/nix
btrfs subvolume create /mnt/persistent
btrfs subvolume create /mnt/snapshots

5. Create empty folders within the root subvolume for future mounts

Later on we will be mounting other btrfs subvolumes to these folders, and root subvolume to the /.

mkdir /mnt/root/boot
mkdir /mnt/root/nix
mkdir /mnt/root/persistent
mkdir /mnt/root/snapshots

6. Create blank snapshot of the root subvolume

This empty snapshot will be used to restore the clean system state for impermanence setup.

mkdir /mnt/snapshots/root

btrfs subvolume snapshot -r /mnt/root /mnt/snapshots/root/blank

7. Unmount the drive and mount subvolumes instead

umount /mnt

mount -o subvol=root /dev/sda2 /mnt
mount -o subvol=nix /dev/sda2 /mnt/nix
mount -o subvol=persistent /dev/sda2 /mnt/persistent
mount -o subvol=snapshots /dev/sda2 /mnt/snapshots

mount /dev/sda1 /mnt/boot

8. Generate basic nixos config

nixos-generate-config --root /mnt

Verify /mnt/etc/nix/hardware-configuration.nix file using nano. It must contain mount options for /nix, /persistent, /snapshots and / being a btrfs subvolumes (options field), /boot being a mount of /dev/sda1, and a swap device /dev/sda3.

Then go to /mnt/etc/nix/configuration.nix and:

1. Set networking.hostName to a proper value.
2. Set networking.networkmanager.enable = true;.
3. In environment.systemPackages enable git, curl, wget, vim and micro (more is better right?).
4. Add flakes support with this: nix.settings.experimental-features = [ "nix-command" "flakes" ];.
5. Allow unfree packages with this: nixpkgs.config.allowUnfree = true;.

9. Proceed NixOS installation and setup root password afterwards

nixos-install

reboot

10. Create password files

Create root.password and <your username>.password files in the /persistent folder containing your accounts' encrypted passwords.

mkpasswd -m sha-512

11. Reproduce this configuration repo

Clone this repo and edit the flakeConfig.json file to setup your user.

sudo git clone https://github.com/krypt0nn/dotfiles /system-flake

sudo nix flake update /system-flake
sudo nixos-rebuild boot --flake /system-flake

12. Restart the system

restart

Done. Welcome to your impermanent NixOS system!

Troubleshooting

1. I lost my account! How do I login?

Boot from the live iso used to install the system. Then:

sudo -i

mount -o subvol=root /dev/sda2 /mnt
mount -o subvol=nix /dev/sda2 /mnt/nix
mount -o subvol=persistent /dev/sda2 /mnt/persistent

nixos-enter

Also you've probably forgot to create accounts' password files. Check out stage 10.