nixos-virtualbox-2025-01-06-22-20-04

machine/nixos-virtualbox/configuration.nix

@@ -17,7 +17,6 @@
     validateSopsFiles = true;
     age = {
       sshKeyPaths = ["/persist/etc/ssh/ssh_host_ed25519_key"];
-      keyFile = "/var/lib/sops-nix/key.txt";
       generateKey = true;
     };
   };
@@ -27,7 +26,43 @@
   boot = {
     initrd = {
       enable = true;
-      supportedFilesystems = ["btrfs"];
+      postResumeCommands = lib.mkAfter ''
+        mkdir -p /mnt
+        # We first mount the btrfs root to /mnt
+        # so we can manipulate btrfs subvolumes.
+        mount -o subvol=/ /dev/sda2 /mnt
+
+        # While we're tempted to just delete /root and create
+        # a new snapshot from /root-blank, /root is already
+        # populated at this point with a number of subvolumes,
+        # which makes `btrfs subvolume delete` fail.
+        # So, we remove them first.
+        #
+        # /root contains subvolumes:
+        # - /root/var/lib/portables
+        # - /root/var/lib/machines
+        #
+        # I suspect these are related to systemd-nspawn, but
+        # since I don't use it I'm not 100% sure.
+        # Anyhow, deleting these subvolumes hasn't resulted
+        # in any issues so far, except for fairly
+        # benign-looking errors from systemd-tmpfiles.
+        btrfs subvolume list -o /mnt/root |
+        cut -f9 -d' ' |
+        while read subvolume; do
+          echo "deleting /$subvolume subvolume..."
+          btrfs subvolume delete "/mnt/$subvolume"
+        done &&
+        echo "deleting /root subvolume..." &&
+        btrfs subvolume delete /mnt/root
+
+        echo "restoring blank /root subvolume..."
+        btrfs subvolume snapshot /mnt/root-blank /mnt/root
+
+        # Once we're done rolling back to a blank snapshot,
+        # we can unmount /mnt and continue on the boot process.
+        umount /mnt
+      '';
     };
   };
 
@@ -36,14 +71,31 @@
     hostName = "nixos-virtualbox"; # Define your hostname.
   };
 
+  nix.settings = {
+    system-features = [
+      "nixos-test"
+      "benchmark"
+      "big-parallel"
+      "gccarch-znver3"
+    ];
+    trusted-substituters = ["https://ai.cachix.org"];
+    trusted-public-keys = ["ai.cachix.org-1:N9dzRK+alWwoKXQlnn0H6aUx0lU/mspIoz8hMvGvbbc="];
+  };
+
+  # nixpkgs.localSystem = {
+  #   gcc.arch = "znver3";
+  #   gcc.tune = "znver3";
+  #   system = "x86_64-linux";
+  # };
+
   programs.nix-ld.enable = true;
 
-  # services = {
-  #   k3s = {
-  #     enable = true;
-  #     role = "server";
-  #   };
-  # };
+  services = {
+    # k3s = {
+    #   enable = true;
+    #   role = "server";
+    # };
+  };
 
   system.stateVersion = "24.11";
 }