nixos/virtualbox-image: set the root fsType to reenable root FS resizing

This otherwise does not eval `:tested` any more, which means no nixos
channel updates.

Regression comes from 0eb6d0735f599fa84e99b727c93681bcae96c845 (#57751)
which added an assertion stopping the use of `autoResize` when the
filesystem cannot be resized automatically.

1 files changed, 1 insertions, 0 deletions

diff --git a/nixos/modules/virtualisation/virtualbox-image.nix b/nixos/modules/virtualisation/virtualbox-image.nix
index 037c0d2f0d8..903411799d3 100644
--- a/nixos/modules/virtualisation/virtualbox-image.nix
+++ b/nixos/modules/virtualisation/virtualbox-image.nix
@@ -94,6 +94,7 @@ in {
     fileSystems."/" = {
       device = "/dev/disk/by-label/nixos";
       autoResize = true;
+      fsType = "ext4";
     };
 
     boot.growPartition = true;