[btrfs] Add role and migrate nix-book

Also switched from trying to override the `nixos` user to instead just
installing home-manager _into_ the `nixos` user. It felt a bit like
fighting the tide otherwise.

build-liveusb.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+
+# Build Live USB ISO from flake configuration
+# Creates an uncompressed ISO suitable for Ventoy and other USB boot tools
+
+set -e
+
+echo "Building Live USB ISO..."
+nix build .#nixosConfigurations.live-usb.config.system.build.isoImage --show-trace
+
+if [ -f "./result/iso/"*.iso ]; then
+    iso_file=$(ls ./result/iso/*.iso)
+    echo "✅ Build complete!"
+    echo "📁 ISO location: $iso_file"
+    echo "💾 Ready for Ventoy or dd to USB"
+else
+    echo "❌ Build failed - no ISO file found"
+    exit 1
+fi

flake.nix

@@ -74,6 +74,22 @@
       ];
     };
 
+    # Live USB ISO configuration
+    nixosConfigurations.live-usb = nixpkgs.lib.nixosSystem rec {
+      system = "x86_64-linux";
+      modules = baseModules ++ [
+        ./machines/live-usb/configuration.nix
+        {
+          home-manager.users.nixos = { ... }: {
+            imports = [ ./home/home.nix ];
+            home.username = nixpkgs.lib.mkForce "nixos";
+            home.homeDirectory = nixpkgs.lib.mkForce "/home/nixos";
+          };
+          home-manager.extraSpecialArgs = { inherit system; };
+        }
+      ];
+    };
+
     homeConfigurations."johno" = inputs.home-manager.lib.homeManagerConfiguration {
       pkgs = inputs.nixpkgs.legacyPackages."x86_64-linux";
       modules = [

machines/live-usb/configuration.nix

@@ -0,0 +1,89 @@
+# Live USB ISO configuration for recovery and installation
+{ pkgs, modulesPath, ... }:
+
+{
+  imports = [
+    # Use minimal installation CD as base
+    (modulesPath + "/installer/cd-dvd/installation-cd-minimal.nix")
+  ];
+
+  # Use roles structure for consistent configuration
+  roles = {
+    audio.enable = true;
+    bluetooth.enable = true;
+    desktop = {
+      enable = true;
+      kde = true;
+      x11 = true;
+      wayland = true;
+      sddm = true;
+    };
+  };
+
+  # Allow unfree packages for broader hardware support
+  nixpkgs.config.allowUnfree = true;
+
+  # Essential packages for system recovery and installation
+  environment.systemPackages = with pkgs; [
+    # Text editors
+    neovim
+    nano
+    
+    # System tools
+    git
+    curl
+    wget
+    htop
+    tree
+    lsof
+    strace
+    
+    # Filesystem tools
+    btrfs-progs
+    e2fsprogs
+    xfsprogs
+    ntfs3g
+    dosfstools
+    
+    # Network tools
+    networkmanager
+    wirelesstools
+    
+    # Hardware tools
+    pciutils
+    usbutils
+    smartmontools
+    
+    # Archive tools
+    unzip
+    p7zip
+    
+    # Development tools (for quick fixes)
+    gcc
+    binutils
+  ];
+
+  # Enable NetworkManager for easy wifi setup
+  networking.networkmanager.enable = true;
+  
+  # Enable SSH daemon for remote access
+  services.openssh = {
+    enable = true;
+    settings = {
+      PermitRootLogin = "yes";
+      PasswordAuthentication = true;
+    };
+  };
+
+  # ISO customization
+  isoImage = {
+    volumeID = "NIXOS-LIVE";
+  };
+
+  # Enable some useful services
+  services.udisks2.enable = true; # For mounting USB drives
+
+  # Hardware support
+  hardware.enableAllFirmware = true;
+  hardware.enableRedistributableFirmware = true;
+}

machines/nix-book/configuration.nix

@@ -39,14 +39,6 @@
 
   boot.kernelPackages = pkgs.linuxPackages_latest;
 
-  # Btrfs deduplication service
-  services.beesd.filesystems = {
-    root = {
-      spec = "/";
-      hashTableSizeMB = 32;  # 128MB per TB recommended, ~225GB = ~32MB
-      verbosity = "err";     # Only show actual problems
-    };
-  };
 
   # Enable networking
   networking.networkmanager.enable = true;

machines/nix-book/hardware-configuration.nix

@@ -10,19 +10,27 @@
 
   boot.initrd.availableKernelModules = [ "xhci_pci" "thunderbolt" "vmd" "nvme" "sdhci_pci" ];
   boot.initrd.kernelModules = [ ];
+  boot.initrd.luks.devices."luks-4126fbd4-bd09-4ece-af0d-6fff414c21b3".device = "/dev/disk/by-uuid/4126fbd4-bd09-4ece-af0d-6fff414c21b3";
   boot.kernelModules = [ "kvm-intel" ];
   boot.extraModulePackages = [ ];
 
-  fileSystems."/" =
-    { device = "/dev/disk/by-uuid/223a44e5-91e2-4272-830e-129166042a1d";
-      fsType = "btrfs";
-      options = [ 
-        "compress=zstd"  # Enable zstd compression for space savings
-        "noatime"        # Don't update access times for performance
-      ];
+  roles.btrfs = {
+    enable = true;
+    filesystems."/dev/disk/by-uuid/223a44e5-91e2-4272-830e-129166042a1d" = {
+      mountpoints = {
+        "/" = {
+          compression = "zstd";
+          extraOptions = [ "noatime" ];
+        };
+      };
+      scrub.enable = true;
+      deduplication = {
+        enable = true;
+        hashTableSizeMB = 32;
+        verbosity = "err";
+      };
+    };
   };
-
-  boot.initrd.luks.devices."luks-4126fbd4-bd09-4ece-af0d-6fff414c21b3".device = "/dev/disk/by-uuid/4126fbd4-bd09-4ece-af0d-6fff414c21b3";
 
   fileSystems."/boot" =
     { device = "/dev/disk/by-uuid/7A0B-CF88";

roles/btrfs/default.nix

@@ -0,0 +1,168 @@
+{ lib, config, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.roles.btrfs;
+in
+{
+  options.roles.btrfs = {
+    enable = mkEnableOption "Enable btrfs filesystem management";
+    
+    filesystems = mkOption {
+      type = types.attrsOf (types.submodule {
+        options = {
+          # Filesystem-level maintenance options
+          scrub = {
+            enable = mkOption { 
+              type = types.bool; 
+              default = true;
+              description = "Enable automatic scrubbing for this filesystem";
+            };
+            interval = mkOption { 
+              type = types.str; 
+              default = "weekly";
+              description = "Scrub interval (systemd timer format)";
+            };
+          };
+          deduplication = {
+            enable = mkOption { 
+              type = types.bool; 
+              default = false;
+              description = "Enable beesd deduplication for this filesystem";
+            };
+            hashTableSizeMB = mkOption { 
+              type = types.int; 
+              default = 1024;
+              description = "Hash table size in MB (should be multiple of 16)";
+            };
+            verbosity = mkOption { 
+              type = types.str; 
+              default = "info";
+              description = "Logging verbosity level";
+            };
+          };
+          balance = {
+            enable = mkOption { 
+              type = types.bool; 
+              default = false;
+              description = "Enable periodic balance operations";
+            };
+            interval = mkOption { 
+              type = types.str; 
+              default = "monthly";
+              description = "Balance interval (systemd timer format)";
+            };
+            dataUsage = mkOption { 
+              type = types.int; 
+              default = 50;
+              description = "Data usage threshold for balance";
+            };
+            metadataUsage = mkOption { 
+              type = types.int; 
+              default = 50;
+              description = "Metadata usage threshold for balance";
+            };
+          };
+          
+          # Mountpoint-based configuration
+          mountpoints = mkOption {
+            type = types.attrsOf (types.submodule {
+              options = {
+                subvolume = mkOption { 
+                  type = types.nullOr types.str; 
+                  default = null;
+                  description = "Subvolume name. If null, uses default subvolume.";
+                };
+                compression = mkOption { 
+                  type = types.str; 
+                  default = "zstd";
+                  description = "Compression algorithm (zstd, lzo, lz4, none)";
+                };
+                autodefrag = mkOption { 
+                  type = types.bool; 
+                  default = false;
+                  description = "Enable automatic defragmentation";
+                };
+                extraOptions = mkOption { 
+                  type = types.listOf types.str; 
+                  default = [];
+                  description = "Additional mount options";
+                };
+              };
+            });
+            default = {};
+            description = "Mountpoint configurations for this filesystem";
+          };
+        };
+      });
+      default = {};
+      description = "Btrfs filesystems configuration";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # Generate fileSystems configuration from mountpoints
+    fileSystems = mkMerge (flatten (mapAttrsToList (device: fsCfg:
+      mapAttrsToList (mountpoint: mountCfg:
+        {
+          ${mountpoint} = {
+            device = device;
+            fsType = "btrfs";
+            options = 
+              (optional (mountCfg.subvolume != null) "subvol=${mountCfg.subvolume}") ++
+              [ "compress=${mountCfg.compression}" ] ++
+              (optional mountCfg.autodefrag "autodefrag") ++
+              mountCfg.extraOptions;
+          };
+        }
+      ) fsCfg.mountpoints
+    ) cfg.filesystems));
+    
+    # Configure scrub service using NixOS built-in
+    services.btrfs.autoScrub = mkIf (any (fs: fs.scrub.enable) (attrValues cfg.filesystems)) {
+      enable = true;
+      interval = "weekly"; # TODO: Make this configurable per filesystem
+      fileSystems = attrNames (filterAttrs (_: fs: fs.scrub.enable) cfg.filesystems);
+    };
+    
+    # Configure beesd for filesystems with deduplication enabled
+    services.beesd.filesystems = mapAttrs' (device: fsCfg: 
+      nameValuePair (replaceStrings ["/"] ["_"] (replaceStrings ["-"] ["_"] device)) {
+        spec = device;
+        hashTableSizeMB = fsCfg.deduplication.hashTableSizeMB;
+        verbosity = fsCfg.deduplication.verbosity;
+      }
+    ) (filterAttrs (_: fs: fs.deduplication.enable) cfg.filesystems);
+    
+    # Custom balance services for filesystems with balance enabled
+    systemd.services = mkMerge (mapAttrsToList (device: fsCfg: mkIf fsCfg.balance.enable {
+      "btrfs-balance-${replaceStrings ["/"] ["-"] (replaceStrings ["-"] ["_"] device)}" = {
+        description = "Balance btrfs filesystem ${device}";
+        script = ''
+          ${pkgs.btrfs-progs}/bin/btrfs balance start \
+            -dusage=${toString fsCfg.balance.dataUsage} \
+            -musage=${toString fsCfg.balance.metadataUsage} \
+            ${device}
+        '';
+        serviceConfig = {
+          Type = "oneshot";
+          Nice = 19;
+          IOSchedulingClass = "idle";
+        };
+      };
+    }) cfg.filesystems);
+    
+    # Balance timers
+    systemd.timers = mkMerge (mapAttrsToList (device: fsCfg: mkIf fsCfg.balance.enable {
+      "btrfs-balance-${replaceStrings ["/"] ["-"] (replaceStrings ["-"] ["_"] device)}" = {
+        description = "Periodic balance for ${device}";
+        wantedBy = [ "timers.target" ];
+        timerConfig = {
+          OnCalendar = fsCfg.balance.interval;
+          Persistent = true;
+        };
+      };
+    }) cfg.filesystems);
+  };
+}

roles/default.nix

@@ -6,6 +6,7 @@ with lib;
   imports = [
     ./audio
     ./bluetooth
+    ./btrfs
     ./desktop
     ./kodi
     ./nfs-mounts