Add support for persistent disks in the hydra iso.

nix/configuration/flake.nix

@@ -3,7 +3,7 @@
 #   output: result/iso/nixos.iso
 
 # Run the ISO image
-#   "$(nix-build '<nixpkgs>' --no-out-link -A 'qemu')/bin/qemu-system-x86_64" \
+#   doas "$(nix-build '<nixpkgs>' --no-out-link -A 'qemu')/bin/qemu-system-x86_64" \
 #        -accel kvm \
 #        -cpu host \
 #        -smp cores=8 \
@@ -12,7 +12,7 @@
 #        -drive if=pflash,format=raw,file="/tmp/OVMF_VARS.fd" \
 #        -nic user,hostfwd=tcp::60022-:22 \
 #        -boot order=d \
-#        -cdrom "$(readlink -f ./result/iso/nixos.iso)" \
+#        -cdrom "$(readlink -f ./result/iso/nixos*.iso)" \
 #        -display vnc=127.0.0.1:0
 #
 # doas cp "$(nix-build '<nixpkgs>' --no-out-link -A 'OVMF.fd')/FV/OVMF_VARS.fd" /tmp/OVMF_VARS.fd

nix/configuration/hosts/hydra/default.nix

@@ -1,9 +1,31 @@
-{ config, pkgs, ... }:
+#
+# Testing:
+# doas "$(nix-build '<nixpkgs>' --no-out-link -A 'qemu')/bin/qemu-system-x86_64" \
+#      -accel kvm \
+#      -cpu host \
+#      -smp cores=8 \
+#      -m 32768 \
+#      -drive "file=$(nix-build '<nixpkgs>' --no-out-link -A 'OVMF.fd')/FV/OVMF.fd,if=pflash,format=raw,readonly=on" \
+#      -drive file=/tmp/localdisk.img,if=none,id=nvm,format=raw \
+#      -device nvme,serial=deadbeef,drive=nvm \
+#      -nic user,hostfwd=tcp::60022-:22 \
+#      -boot order=d \
+#      -cdrom "$(readlink -f /persist/machine_setup/nix/configuration/result/iso/nixos*.iso)" \
+#      -display vnc=127.0.0.1:0
+#
+
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
 {
   imports = [
-    ./hardware-configuration.nix
     ./disk-config.nix
+    ./hardware-configuration.nix
     ./optimized_build.nix
+    ./vm_disk.nix
   ];
 
   # Generate with `head -c4 /dev/urandom | od -A none -t x4`
@@ -21,9 +43,10 @@
 
   me.emacs_flavor = "plainmacs";
   me.graphical = false;
-  me.zsh.enable = true;
+  me.vm_disk.enable = true;
   me.wireguard.activated = [ ];
   me.wireguard.deactivated = [ ];
+  me.zsh.enable = true;
 
   # Trust this key so nix running as root can ssh into hydra.
   users.users.talexander.openssh.authorizedKeys.keys = [

nix/configuration/hosts/hydra/vm_disk.nix

@@ -0,0 +1,77 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+{
+  imports = [ ];
+
+  options.me = {
+    vm_disk.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether we want to mount the local disk for persistent storage.";
+    };
+  };
+
+  config = lib.mkIf config.me.vm_disk.enable (
+    lib.mkMerge [
+      {
+        # Mount the local disk
+        fileSystems = {
+          "/.disk" = lib.mkForce {
+            device = "/dev/nvme0n1p1";
+            fsType = "ext4";
+            options = [
+              "noatime"
+              "discard"
+            ];
+            neededForBoot = true;
+          };
+
+          "/persist" = {
+            fsType = "none";
+            device = "/.disk/persist";
+            options = [
+              "bind"
+              "rw"
+            ];
+            depends = [
+              "/.disk/persist"
+            ];
+          };
+
+          "/state" = {
+            fsType = "none";
+            device = "/.disk/state";
+            options = [
+              "bind"
+              "rw"
+            ];
+            depends = [
+              "/.disk/state"
+            ];
+          };
+
+          "/nix/store" = lib.mkForce {
+            fsType = "overlay";
+            device = "overlay";
+            options = [
+              "lowerdir=/nix/.ro-store"
+              "upperdir=/.disk/persist/store"
+              "workdir=/.disk/state/work"
+            ];
+            depends = [
+              "/nix/.ro-store"
+              "/.disk/persist/store"
+              "/.disk/state/work"
+            ];
+          };
+        };
+      }
+    ]
+  );
+}