singularity, apptainer: adjust dependencies

pkgs/applications/virtualization/singularity/generic.nix

@@ -36,7 +36,9 @@ in
 , conmon
 , coreutils
 , cryptsetup
+, e2fsprogs
 , fakeroot
+, fuse2fs ? e2fsprogs.fuse2fs
 , go
 , gpgme
 , libseccomp
@@ -117,15 +119,19 @@ in
     which
   ];
 
+  # See the `control` file of the Debian package from upstream repos
+  # for build-time dependencies and run-time utilities
+  # apptainer/apptainer: https://github.com/apptainer/apptainer/blob/main/dist/debian/control
+  # sylabs/singularity: https://github.com/sylabs/singularity/blob/main/debian/control
+
   buildInputs = [
     bash # To patch /bin/sh shebangs.
     conmon
     cryptsetup
     gpgme
     libuuid
     openssl
-    squashfsTools
-    squashfuse
+    squashfsTools # Required at build time by SingularityCE
   ]
   ++ lib.optional enableNvidiaContainerCli nvidia-docker
   ++ lib.optional enableSeccomp libseccomp
@@ -148,6 +154,7 @@ in
     bash
     coreutils
     cryptsetup # cryptsetup
+    fuse2fs # Mount ext3 filesystems
     go
     privileged-un-utils
     squashfsTools # mksquashfs unsquashfs # Make / unpack squashfs image
@@ -197,7 +204,11 @@ in
     wrapProgram "$out/bin/${projectName}" \
       --prefix PATH : "${lib.makeBinPath [
         fakeroot
-        squashfsTools # Singularity (but not Apptainer) expects unsquashfs from the host PATH
+        fuse2fs # Apptainer uses fuse2fs to mount ext3 filesystems
+        squashfsTools
+        # Apptainer expect squashfuse from the host PATH to mount squashfs
+        # or it will fall back to extracting.
+        squashfuse
       ]}"
     # Make changes in the config file
     ${lib.optionalString enableNvidiaContainerCli ''

pkgs/applications/virtualization/singularity/packages.nix

@@ -63,6 +63,11 @@ let
       extraMeta.homepage = "https://sylabs.io/";
     })
     {
+      # Unneeded for SingularityCE
+      e2fsprogs = null; # for e2fsprogs.f2fs only
+      fuse2fs = null;
+      squashfuse = null;
+
       defaultToSuid = true;
     };