feat: activate impermanence on gallifrey

machines/gallifrey/hardware.nix

@@ -1,7 +1,12 @@
 # Do not modify this file!  It was generated by ‘nixos-generate-config’
 # and may be overwritten by future invocations.  Please make changes
 # to /etc/nixos/configuration.nix instead.
-{ lib, modulesPath, ... }:
+{
+  lib,
+  modulesPath,
+  pkgs,
+  ...
+}:
 
 {
   imports = [
@@ -18,6 +23,12 @@
   boot.kernelModules = [ ];
   boot.extraModulePackages = [ ];
 
+  boot.initrd.postDeviceCommands = ''
+    lvm lvremove --force /dev/mainpool/root || :
+    yes | lvm lvcreate --size 100G --name root mainpool
+    ${pkgs.e2fsprogs}/bin/mkfs.ext4 /dev/mainpool/root
+  '';
+
   # Enables DHCP on each ethernet and wireless interface. In case of scripted networking
   # (the default) this is the recommended approach. When using systemd-networkd it's
   # still possible to use this option, but it's recommended to use it in conjunction