Rename some hostnames

hosts/tower/boot/default.nix

@@ -0,0 +1,64 @@
+{ config, pkgs, ... }:
+let
+  commonKernelParams = [
+    # Nvidia settings
+    "nvidia_drm.fbdev=1"
+    "nouveau.config=NvGspRm=1"
+
+    # VM/GPU passthrough
+    "amd_iommu=on"
+    "iommu=pt"
+    "nested=1"
+
+    # Virtualization nonsense
+    "transparent_hugepage=never"
+
+    # Isolate devices into IOMMU groups
+    "pcie_acs_override=downstream,multifunction"
+    "pci=routeirq"
+  ];
+in {
+  boot = {
+    # Must be unstable for newest NVIDIA drivers, must be Zen for IOMMU isolation
+    kernelPackages = pkgs.unstable.linuxPackages_zen;
+    kernel.sysctl."vm.max_map_count" = 2147483642;
+    kernelParams = commonKernelParams ++ [ "vfio-pci.ids=10de:1f82,10de:10fa" ];
+    blacklistedKernelModules = [ "pcspkr" ];
+
+    initrd.systemd = {
+      enable = true;
+      services.root-reset = {
+        description = "Reset root and snapshot last boot";
+        wantedBy = [ "initrd.target" ];
+        before = [ "sysroot.mount" ];
+        after = [ "dev-${config.networking.hostName}-root.device" ];
+        unitConfig.DefaultDependencies = "no";
+        serviceConfig.Type = "oneshot";
+        script = ''
+          mkdir -p /mnt
+          mount /dev/${config.networking.hostName}/root /mnt
+
+          if [[ -e /mnt/prev ]]; then
+            btrfs subvolume delete /mnt/prev
+          fi
+
+          btrfs subvolume snapshot /mnt/root /mnt/prev
+
+          btrfs subvolume list -o /mnt/root | cut -f9 -d' ' | while read subvolume; do
+            btrfs subvolume delete "/mnt/$subvolume"
+          done
+
+          btrfs subvolume delete /mnt/root
+          btrfs subvolume create /mnt/root
+
+          umount /mnt
+        '';
+      };
+    };
+  };
+
+  # Use second GPU on boot
+  specialisation.gputwo.configuration = {
+    boot.kernelParams = commonKernelParams ++ [ "vfio-pci.ids=10de:2504,10de:228e" ];
+  };
+}