My NixOS configurations

Here's my ephemeral NixOS setup files.

I'm just starting out with Nix, so it's not too much (for now).

Some details:

Inspired by tmpfs as root, erase your darlings and encrypted btrfs root with opt-in state.

Works with a tmpfs root (and home, using home-manager) file system, plus an encrypted btrfs partition with subvolumes for everything else: nix (Nix store), data (Persistent and writable documents, games, mounted with impermanence) and dotfiles (This repo).

Todos

• Learn flakes (seems cool)
• Improve secret management (for now it all depends on my pgp key stored on data, waiting on my yubikey)

How to setup

Note: Remember to tweak (specially hostname and username) as necessary

Create partitions

First, create your boot partition (usually vfat) and btrfs partition (i usually encrypt it).

We'll create a few subvolumes:

• nix For (disposable) nix store data, no need to set snapshots.
• dotfiles For configuration files, will be managed by home-manager as write-only, we'll also bind the nixos directory to /etc/nixos shortly. Intended to be tracked by git
• data For persistent data, will be mounted writable. I suggest setting up snpashots.

First mount your btrfs. Assuming you opened the encrypted btrfs partition at nixenc:

mount -t btrfs /dev/mapper/nixenv /mnt

Then, create subvolumes, and umount the partition when done:

btrfs subvolume create /mnt/nix
btrfs subvolume create /mnt/dotfiles
btrfs subvolume create /mnt/data
umount /mnt

Of course, you can set this up in any other way you prefer, just remember to adapt the mount commands as necessary.

Mountpoints

Time to mount (my ESP is at /dev/nvme0n1p1, and i'm assuming you find 2gb of tmpfs storage accetable):

mount -t tmpfs -o size=2G,mode=755 none /mnt

mkdir -p /mnt/{boot,nix,etc/nixos,data,dotfiles}

mount /dev/nvme0n1p1 /mnt/boot

mount -o subvol=nix,compress=zstd,noatime /dev/mapper/nixenc /mnt/nix
mount -o subvol=dotfiles,compress=zstd,noatime /dev/mapper/nixenc /mnt/dotfiles
mount -o subvol=data,compress=zstd,noatime /dev/mapper/nixenc /mnt/data

Base config

Clone the repo:

cd /mnt/dotfiles
git clone git@github.com:Misterio77/nix-config.git

Bind the dotfiles config to our new system /etc/nixos:

mount -o bind /mnt/dotfiles/nixos /mnt/etc/nixos

Create your (hashed) password:

mkpasswd -m sha-512 > nixos/password.nix

Finally, generate your hardware config: nixos-generate-config --root /mnt