My NixOS Configuration

A general NixOS flake configuration, currently tailored for my System76 Serval WS laptop. Utilizes configurations from my existing dotfiles.

Features:

Btrfs on LUKS encryption
Impermanence (ephemeral root filesystem)
Sway/Wayland desktop environment (seatd + auto-login)
System76 hardware support + NVIDIA GPU + CUDA
Home Manager for user environment
zram swap with zstd compression
Catppuccin theme (GTK/Qt) with Papirus icons
VM and ISO build targets for testing

Quick Start: Test in VM

# run the VM (builds and launches QEMU)
nix run .#vm

# login: braden / test

The VM includes impermanence - root (/) resets on each boot while /home and /persist survive.

Quick Start: Build Live ISO

# build the ISO for hardware testing
nix build .#iso

# write to USB (replace /dev/sdX with your device)
sudo dd if=result/iso/*.iso of=/dev/sdX bs=4M status=progress

# boot and login: braden / nixos (or nixos / nixos)

The ISO includes the full desktop environment for testing.

Directory Structure

├── flake.nix                 # main entry point
├── hosts/
│   ├── braden-serval-ws/     # System76 Serval WS config
│   │   ├── default.nix
│   │   ├── disko.nix         # LUKS + Btrfs partitioning
│   │   ├── hardware.nix
│   │   └── persistence.nix   # impermanence config
│   ├── vm/                   # VM for testing
│   │   ├── default.nix
│   │   ├── disko.nix
│   │   └── persistence.nix
│   └── iso/                  # Live ISO for hardware testing
│       └── default.nix
├── modules/
│   ├── core/                 # boot, nix, users, locale, zram, packages
│   ├── desktop/              # sway, seatd, audio, fonts
│   ├── hardware/             # system76, nvidia, cuda, bluetooth
│   └── services/             # networking (ssh, avahi), btrbk
└── home/                     # Home Manager config
    ├── shell/                # zsh (oh-my-zsh), starship, direnv, gpg
    ├── terminal/             # alacritty
    ├── editor/               # neovim + AstroNvim
    ├── desktop/              # sway, waybar, wofi, mako
    ├── apps/                 # git, dev-tools, jetbrains
    └── scripts/              # utility scripts from dotfiles

Installation on Hardware

Prerequisites

NixOS minimal installer USB
This repository cloned or accessible

Step 1: Boot Installer and Prepare

# clone this repo
nix-shell -p git
git clone https://github.com/BradenM/nixos /tmp/nixos
cd /tmp/nixos

Step 2: Partition Disk with Disko

# set LUKS password
echo "super-secret-password" > /tmp/disk-password

# run disko to partition and format
sudo nix --experimental-features "nix-command flakes" run \
  github:nix-community/disko -- \
  --mode disko ./hosts/braden-serval-ws/disko.nix

This creates:

/dev/nvme0n1p1 - 1GB EFI partition → /boot
/dev/nvme0n1p2 - LUKS encrypted → Btrfs with subvolumes

Step 3: Create Blank Snapshot for Impermanence

# mount btrfs root
sudo mount -t btrfs -o subvol=/ /dev/mapper/cryptroot /mnt

# create read-only blank snapshot
sudo btrfs subvolume snapshot -r /mnt/@root /mnt/@root-blank

sudo umount /mnt

Step 4: Generate Hardware Configuration

# mount filesystems
sudo mount -t btrfs -o subvol=@root,compress=zstd,noatime /dev/mapper/cryptroot /mnt
sudo mkdir -p /mnt/{home,nix,persist,var/log,boot}
sudo mount -t btrfs -o subvol=@home,compress=zstd,noatime /dev/mapper/cryptroot /mnt/home
sudo mount -t btrfs -o subvol=@nix,compress=zstd,noatime /dev/mapper/cryptroot /mnt/nix
sudo mount -t btrfs -o subvol=@persist,compress=zstd,noatime /dev/mapper/cryptroot /mnt/persist
sudo mount -t btrfs -o subvol=@log,compress=zstd,noatime /dev/mapper/cryptroot /mnt/var/log
sudo mount /dev/nvme0n1p1 /mnt/boot

# generate hardware config
sudo nixos-generate-config --root /mnt --show-hardware-config > /tmp/hardware.nix

Review /tmp/hardware.nix and merge relevant parts into target host.

Step 5: Set User Passwords

sudo mkdir -p /mnt/persist/passwords

# set user password
echo "$(mkpasswd -m sha-512)" | sudo tee /mnt/persist/passwords/braden

# set root password (for emergency access)
echo "$(mkpasswd -m sha-512)" | sudo tee /mnt/persist/passwords/root

# secure permissions
sudo chmod 600 /mnt/persist/passwords/*

Step 6: Install

sudo nixos-install --flake .#braden-serval-ws --no-root-passwd

Step 7: Reboot

sudo reboot

Post-Installation: Managing Your Configuration

After boot, clone the NixOS configuration to a persistent location.

Clone Configuration

# clone to persist directory (survives impermanence resets)
git clone https://github.com/BradenM/nixos /persist/nixos

# or clone to home (also persists via @home subvolume)
git clone https://github.com/BradenM/nixos ~/nixos

Making Changes

cd /persist/nixos  # or ~/nixos

# edit configuration files
nvim home/default.nix

# test changes
sudo nixos-rebuild test --flake .#braden-serval-ws

# apply changes
sudo nixos-rebuild switch --flake .#braden-serval-ws

# commit and push
git add -A && git commit -m "description of changes"
git push

Configuration Locations

Location	Persists	Notes
`/persist/nixos`	Yes (bind-mounted)	Recommended for system config
`~/nixos`	Yes (@home subvolume)	Alternative location
`/etc/nixos`	Yes (bind-mounted)	Legacy location, not used by flakes
`/tmp/*`	No	Lost on reboot

Common Operations

Rebuild System

# test configuration (doesn't switch)
sudo nixos-rebuild test --flake .#braden-serval-ws

# switch to new configuration
sudo nixos-rebuild switch --flake .#braden-serval-ws

# build for next boot only
sudo nixos-rebuild boot --flake .#braden-serval-ws

Update Flake Inputs

# update all inputs
nix flake update

# update specific input
nix flake lock --update-input nixpkgs

Rollback

# list generations
sudo nix-env --list-generations --profile /nix/var/nix/profiles/system

# rollback to previous generation
sudo nixos-rebuild switch --rollback

# boot menu also shows previous generations

Garbage Collection

# remove old generations (keeps last 14 days by default)
sudo nix-collect-garbage -d

# remove specific generations
sudo nix-env --delete-generations +5 --profile /nix/var/nix/profiles/system

Impermanence

Root (/) is ephemeral - it resets to a blank state on every boot. Only explicitly declared paths persist.

What Persists

Via /persist (impermanence module):

/etc/nixos - NixOS configuration
/etc/NetworkManager/system-connections - WiFi passwords
/etc/ssh - SSH host keys
/etc/machine-id - Machine identifier
/var/lib/nixos - NixOS state
/var/lib/systemd - Systemd state
/var/lib/bluetooth - Bluetooth pairings

Via dedicated subvolumes:

/home - User home directories
/nix - Nix store
/var/log - System logs

How It Works

On boot, initrd runs a rollback script
The @root subvolume is deleted
A fresh @root is created from @root-blank snapshot
The impermanence module bind-mounts paths from /persist

btrbk Snapshots

Automatic hourly snapshots via btrbk:

# list snapshots
sudo btrbk list

# show snapshot details
sudo ls -la /mnt/btrfs-root/snapshots/

# manual snapshot
sudo btrbk run

Recovery from Snapshot

# mount btrfs root
sudo mount -t btrfs -o subvol=/ /dev/mapper/cryptroot /mnt

# list available snapshots
ls /mnt/snapshots/

# restore home from snapshot (example)
sudo btrfs subvolume delete /mnt/@home
sudo btrfs subvolume snapshot /mnt/snapshots/home.20240101T120000 /mnt/@home

sudo umount /mnt
sudo reboot

Troubleshooting

Impermanence Rollback Fails

# boot with init=/bin/sh
# mount and manually create blank snapshot
mount -t btrfs -o subvol=/ /dev/mapper/cryptroot /mnt
btrfs subvolume snapshot -r /mnt/@root /mnt/@root-blank

Build Targets

Target	Command	Description
Hardware	`nixos-rebuild switch --flake .#braden-serval-ws`	Full System76 Serval WS config
VM	`nix run .#vm`	QEMU VM with impermanence
ISO	`nix build .#iso`	Live ISO for hardware testing

ISO Details

The ISO is configured for testing on actual hardware before installation:

Includes full Sway desktop with Home Manager config
Manual TTY login (no auto-login), run sway after login to start desktop
Login as braden (password: nixos) for full desktop
Login as nixos (password: nixos) for basic testing
SSH enabled for remote access (root login allowed for installation)

Name		Name	Last commit message	Last commit date
Latest commit History 93 Commits
home		home
hosts		hosts
modules		modules
.gitignore		.gitignore
README.md		README.md
flake.lock		flake.lock
flake.nix		flake.nix

BradenM/nixos

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