Commit be4e7ef9 authored by Raito Bezarius's avatar Raito Bezarius
Browse files

nixos/qemu-vm: fix diskless VMs 

Previously, it was possible to run with a tmpfs / with
`virtualisation.diskImage = null;`, this was likely broken by my changes
in 4b4e4c3e.

It is reintroduced by disabling properly the bootloader for now, as it
is complicated to make it work with.
parent 6d691716

nixos/modules/virtualisation/qemu-vm.nix

+19 −8
Original line number Diff line number Diff line
@@ -264,7 +264,7 @@ let 
  suggestedRootDevice = {

    "efi_bootloading_with_default_fs" = "${cfg.bootLoaderDevice}2";

    "legacy_bootloading_with_default_fs" = "${cfg.bootLoaderDevice}1";

    "direct_boot_with_default_fs" = cfg.bootLoaderDevice;

    "direct_boot_with_default_fs" = lookupDriveDeviceName "root" cfg.qemu.drives;

    # This will enforce a NixOS module type checking error

    # to ask explicitly the user to set a rootDevice.

    # As it will look like `rootDevice = lib.mkDefault null;` after
@@ -336,14 +336,14 @@ in 


    virtualisation.bootLoaderDevice =

      mkOption {

        type = types.path;

        default = lookupDriveDeviceName "root" cfg.qemu.drives;

        defaultText = literalExpression ''lookupDriveDeviceName "root" cfg.qemu.drives'';

        type = types.nullOr types.path;

        default = if cfg.useBootLoader then lookupDriveDeviceName "root" cfg.qemu.drives else null;

        defaultText = literalExpression ''if cfg.useBootLoader then lookupDriveDeviceName "root" cfg.qemu.drives else null;'';

        example = "/dev/vda";

        description =

          lib.mdDoc ''

            The disk to be used for the boot filesystem.

            By default, it is the same disk as the root filesystem.

            By default, it is the same disk as the root filesystem if you use a bootloader, otherwise it's null.

          '';

        };
@@ -837,6 +837,16 @@ in 
                  The address must be in the default VLAN (10.0.2.0/24).

              '';

            }

          { assertion = cfg.useBootLoader -> cfg.diskImage != null;

            message =

              ''

                Currently, bootloaders cannot be used with a tmpfs disk image.

                It would require some rework in the boot configuration mechanism

                to detect the proper boot partition in UEFI scenarios for example.



                If you are interested into this feature, please open an issue or open a pull request.

              '';

          }

        ]));



    warnings =
@@ -863,7 +873,8 @@ in 
    # legacy and UEFI. In order to avoid this, we have to put "nodev" to force UEFI-only installs.

    # Otherwise, we set the proper bootloader device for this.

    # FIXME: make a sense of this mess wrt to multiple ESP present in the system, probably use boot.efiSysMountpoint?

    boot.loader.grub.device = mkVMOverride (if cfg.useEFIBoot then "nodev" else cfg.bootLoaderDevice);

    boot.loader.grub.enable = cfg.useBootLoader;

    boot.loader.grub.device = mkIf cfg.useBootLoader (mkVMOverride (if cfg.useEFIBoot then "nodev" else cfg.bootLoaderDevice));

    boot.loader.grub.gfxmodeBios = with cfg.resolution; "${toString x}x${toString y}";

    virtualisation.rootDevice = mkDefault suggestedRootDevice;
@@ -871,13 +882,13 @@ in 


    boot.loader.supportsInitrdSecrets = mkIf (!cfg.useBootLoader) (mkVMOverride false);



    boot.initrd.extraUtilsCommands = lib.mkIf (cfg.useDefaultFilesystems && !config.boot.initrd.systemd.enable)

    boot.initrd.extraUtilsCommands = lib.mkIf (cfg.useDefaultFilesystems && !config.boot.initrd.systemd.enable && cfg.diskImage != null)

      ''

        # We need mke2fs in the initrd.

        copy_bin_and_libs ${pkgs.e2fsprogs}/bin/mke2fs

      '';



    boot.initrd.postDeviceCommands = lib.mkIf (cfg.useDefaultFilesystems && !config.boot.initrd.systemd.enable)

    boot.initrd.postDeviceCommands = lib.mkIf (cfg.useDefaultFilesystems && !config.boot.initrd.systemd.enable && cfg.diskImage != null)

      ''

        # If the disk image appears to be empty, run mke2fs to

        # initialise.