From fc4607ec20ae60907a7b980f146566b41e320b71 Mon Sep 17 00:00:00 2001
From: Christoph Cullmann <cullmann@kde.org>
Date: Wed, 29 May 2024 21:07:09 +0200
Subject: [PATCH] prepare for ZFS

---
 common.nix                      | 46 +++++++++------------------------
 mini/configuration.nix          |  8 +++---
 neko/configuration.nix          |  8 +++---
 neko/hardware-configuration.nix |  5 ----
 neko/install.txt                |  7 +++++
 5 files changed, 27 insertions(+), 47 deletions(-)

diff --git a/common.nix b/common.nix
index fedcc6e..98c2200 100644
--- a/common.nix
+++ b/common.nix
@@ -25,8 +25,9 @@ in
   # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
   system.stateVersion = "23.05"; # Did you read the comment?
 
-  # use the latest kernel
-  boot.kernelPackages = pkgs.linuxPackages_latest;
+  # use the latest kernel with ZFS support and enable that file system
+  boot.kernelPackages = config.boot.zfs.package.latestCompatibleLinuxPackages;
+  boot.supportedFilesystems = [ "zfs" ];
 
   # Use the systemd-boot EFI boot loader.
   boot.loader.systemd-boot.enable = true;
@@ -38,18 +39,21 @@ in
   # we want to be able to do a memtest
   boot.loader.systemd-boot.memtest86.enable = true;
 
+  # use systemd early
+  boot.initrd.systemd.enable = true;
+
   # setup the console stuff early
   console.earlySetup = true;
 
   # swap to RAM
   zramSwap.enable = true;
 
-  # root file system from encrypted disk
+  # root file system in RAM
   fileSystems."/" =
-    { device = "/dev/mapper/crypt-system";
-      fsType = "btrfs";
+    { device = "none";
+      fsType = "tmpfs";
       neededForBoot = true;
-      options = [ "subvol=root" "noatime" "nodiratime" ];
+      options = [ "defaults" "size=8G" "mode=755" ];
     };
 
   # nix store file system from encrypted disk
@@ -95,32 +99,6 @@ in
       depends = [ "/data" ];
     };
 
-  # impermanence root setup
-  boot.initrd.postDeviceCommands = pkgs.lib.mkAfter ''
-    mkdir /btrfs_tmp
-    mount /dev/mapper/crypt-system /btrfs_tmp
-    if [[ -e /btrfs_tmp/root ]]; then
-        mkdir -p /btrfs_tmp/old_roots
-        timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
-        mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
-    fi
-
-    delete_subvolume_recursively() {
-        IFS=$'\n'
-        for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
-            delete_subvolume_recursively "/btrfs_tmp/$i"
-        done
-        btrfs subvolume delete "$1"
-    }
-
-    for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +7); do
-        delete_subvolume_recursively "$i"
-    done
-
-    btrfs subvolume create /btrfs_tmp/root
-    umount /btrfs_tmp
-  '';
-
   # keep some stuff persistent
   environment.persistence."/nix/persistent" = {
     hideMounts = true;
@@ -554,8 +532,8 @@ in
       # aliases
       shellAliases = {
         # system build/update/cleanup
-        update = "sudo nixos-rebuild switch";
-        upgrade = "sudo nixos-rebuild switch --upgrade";
+        update = "sudo nixos-rebuild boot";
+        upgrade = "sudo nixos-rebuild boot --upgrade";
         gc = "sudo nix-collect-garbage --delete-older-than 7d";
         verify = "sudo nix --extra-experimental-features nix-command store verify --all";
         optimize = "sudo nix --extra-experimental-features nix-command store optimise";
diff --git a/mini/configuration.nix b/mini/configuration.nix
index 44881cc..23f103c 100644
--- a/mini/configuration.nix
+++ b/mini/configuration.nix
@@ -17,10 +17,10 @@
   # amd graphics
   hardware.opengl.extraPackages = with pkgs; [ amdvlk rocm-opencl-icd rocm-opencl-runtime ];
 
-  # our hostname
+  # our hostname and an ID for ZFS
   networking.hostName = "mini";
+  networking.hostId = "e925ccfb";
 
-  # use NetworkManager
-  networking.useDHCP = false;
-  networking.networkmanager.enable = true;
+  # classic dhcpcd
+  networking.networkmanager.enable = false;
 }
diff --git a/neko/configuration.nix b/neko/configuration.nix
index 6e8d8e0..7c42433 100644
--- a/neko/configuration.nix
+++ b/neko/configuration.nix
@@ -17,10 +17,10 @@
   # intel graphics
   hardware.opengl.extraPackages = with pkgs; [ intel-media-driver intel-compute-runtime ];
 
-  # our hostname
+  # our hostname and an ID for ZFS
   networking.hostName = "neko";
+  networking.hostId = "cf5a5ee6";
 
-  # use NetworkManager
-  networking.useDHCP = false;
-  networking.networkmanager.enable = true;
+  # classic dhcpcd
+  networking.networkmanager.enable = false;
 }
diff --git a/neko/hardware-configuration.nix b/neko/hardware-configuration.nix
index 62c1669..50fa14c 100644
--- a/neko/hardware-configuration.nix
+++ b/neko/hardware-configuration.nix
@@ -10,11 +10,6 @@
   boot.initrd.kernelModules = [ "i915" ];
   boot.kernelModules = [ "kvm-intel" ];
 
-  # use the right soundcard
-  boot.extraModprobeConfig = ''
-    options snd_hda_intel enable=0,1
-  '';
-
   # don't check for split locks, for KVM and Co.
   boot.kernelParams = [ "split_lock_detect=off" ];
 
diff --git a/neko/install.txt b/neko/install.txt
index 646f1ef..66da359 100644
--- a/neko/install.txt
+++ b/neko/install.txt
@@ -21,6 +21,13 @@ nix --extra-experimental-features flakes --extra-experimental-features nix-comma
 
 sudo dd if=result/iso/nixos-24.05.20240108.317484b-x86_64-linux.iso of=/dev/sda bs=4M conv=fsync
 
+# good ZFS links
+
+https://openzfs.github.io/openzfs-docs/Getting%20Started/NixOS/Root%20on%20ZFS.html
+https://carjorvaz.com/posts/installing-nixos-with-root-on-tmpfs-and-encrypted-zfs-on-a-netcup-vps/
+https://astrid.tech/2021/12/17/0/two-disk-encrypted-zfs/
+https://mzhang.io/posts/2022-05-09-installing-nixos-on-encrypted-zfs/
+
 #
 # enable ssh for root
 #