nixos/filesystems: init erofs

Enable using an erofs filesystem as one of the filesystems needed to
boot the system. This is useful for example in image based deployments
where the Nix store is mounted read only.
[erofs](https://docs.kernel.org/filesystems/erofs.html) offers multiple
benefits over older filesystems like squashfs. Skip fsck.erofs because
it is still experimental.

1 files changed, 21 insertions, 0 deletions

diff --git a/nixos/modules/tasks/filesystems/erofs.nix b/nixos/modules/tasks/filesystems/erofs.nix
new file mode 100644
index 000000000000..a3d657669350
--- /dev/null
+++ b/nixos/modules/tasks/filesystems/erofs.nix
@@ -0,0 +1,21 @@
+{ config, lib, pkgs, ... }:
+
+let
+
+  inInitrd = lib.any (fs: fs == "erofs") config.boot.initrd.supportedFilesystems;
+  inSystem = lib.any (fs: fs == "erofs") config.boot.supportedFilesystems;
+
+in
+
+{
+  config = lib.mkIf (inInitrd || inSystem) {
+
+    system.fsPackages = [ pkgs.erofs-utils ];
+
+    boot.initrd.availableKernelModules = lib.mkIf inInitrd [ "erofs" ];
+
+    # fsck.erofs is currently experimental and should not be run as a
+    # privileged user. Thus, it is not included in the initrd.
+
+  };
+}