diff --git a/assemblers/io.weldr.qcow2 b/assemblers/io.weldr.qcow2
new file mode 100755
index 00000000..2938a950
--- /dev/null
+++ b/assemblers/io.weldr.qcow2
@@ -0,0 +1,82 @@
+#!/usr/bin/python3
+
+import contextlib
+import json
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+def tree_size(tree):
+    size = 0
+    for root, dirs, files in os.walk(tree):
+        for entry in files + dirs:
+            path = os.path.join(root, entry)
+            size += os.stat(path, follow_symlinks=False).st_size
+    return size
+
+@contextlib.contextmanager
+def mount(source, dest, *options):
+    os.makedirs(dest, 0o755, True)
+    subprocess.run(["mount", *options, source, dest], check=True)
+    try:
+        yield
+    finally:
+        subprocess.run(["umount", "-R", dest], check=True)
+
+@contextlib.contextmanager
+def mount_api(dest):
+    with mount("/dev", f"{dest}/dev", "-o", "rbind"), \
+         mount("/proc", f"{dest}/proc", "-o", "rbind"), \
+         mount("/sys", f"{dest}/sys", "-o", "rbind"), \
+         mount("none", f"{dest}/run", "-t", "tmpfs"):
+             yield
+
+@contextlib.contextmanager
+def loop_device(image):
+    r = subprocess.run(["losetup", "-f"], stdout=subprocess.PIPE, encoding="utf-8", check=True)
+    loop = r.stdout.strip()
+    r = subprocess.run(["losetup", loop, "-P", image], check=True)
+    try:
+        yield loop
+    finally:
+        subprocess.run(["losetup", "-d", loop], check=True)
+
+def main(tree, input_dir, options):
+    filename = options["filename"]
+    partition_table_id = options["partition_table_id"]
+    root_fs_uuid = options["root_fs_uuid"]
+
+    # Create a working directory on a tmpfs, maybe we should implicitly
+    # always do this.
+    with tempfile.TemporaryDirectory() as workdir:
+        image = f"{workdir}/image.raw"
+        mountpoint = f"{workdir}/mnt"
+
+        # Create an empty image file of the right size
+        size = int(tree_size(tree) * 1.2)
+        subprocess.run(["truncate", "--size", str(size), image], check=True)
+
+        # Set up the partition table of the image
+        partition_table = "label: mbr\nlabel-id: {partition_table_id}\nbootable, type=83"
+        subprocess.run(["sfdisk", "-q", image], input=partition_table, encoding='utf-8', check=True)
+
+        # Mount the created image as a loopback device
+        with loop_device(image) as loop:
+            # Populate the first partition of the image with an ext4 fs and fill it with the contents of the
+            # tree we are operating on.
+            subprocess.run(["mkfs.ext4", "-d", tree, "-U", root_fs_uuid, f"{loop}p1"], check=True)
+
+            # Install grub2 into the boot sector of the image
+            # It is unclear why chrooting into the image is required.
+            with mount(f"{loop}p1", mountpoint):
+                with mount_api(mountpoint):
+                    subprocess.run(["chroot", mountpoint, "grub2-install", "--no-floppy", "--target", "i386-pc", loop], check=True)
+
+        subprocess.run(["qemu-img", "convert", "-O" "qcow2", "-c", image, filename], check=True)
+
+if __name__ == '__main__':
+    args = json.load(sys.stdin)
+    r = main(args["tree"], args["input_dir"], args["options"])
+    sys.exit(r)
diff --git a/stages/io.weldr.qcow2 b/stages/io.weldr.qcow2
deleted file mode 100755
index cde80f77..00000000
--- a/stages/io.weldr.qcow2
+++ /dev/null
@@ -1,78 +0,0 @@
-#!/usr/bin/python3
-
-import contextlib
-import json
-import os
-import subprocess
-import sys
-import tempfile
-
-def tree_size(tree):
-    size = 0
-    for root, dirs, files in os.walk(tree):
-        for entry in files + dirs:
-            path = os.path.join(root, entry)
-            size += os.stat(path, follow_symlinks=False).st_size
-    return size
-
-@contextlib.contextmanager
-def mount(source, dest, *options):
-    os.makedirs(dest, 0o755, True)
-    subprocess.run(["mount", *options, source, dest], check=True)
-    try:
-        yield
-    finally:
-        subprocess.run(["umount", dest], check=True)
-
-@contextlib.contextmanager
-def mount_image(device, dest):
-    with mount(device, dest), \
-         mount("/dev", f"{dest}/dev", "--bind"), \
-         mount("/proc", f"{dest}/proc", "--bind"), \
-         mount("/sys", f"{dest}/sys", "--bind"):
-             yield
-
-@contextlib.contextmanager
-def loop_device(image):
-    r = subprocess.run(["losetup", "--show", "-f", "-P", image], stdout=subprocess.PIPE, encoding="utf-8", check=True)
-    loop = r.stdout.strip()
-    try:
-        yield loop
-    finally:
-        subprocess.run(["losetup", "-d", loop], check=True)
-
-def main(tree, options):
-    target = options["target"])
-
-    size = tree_size(tree)
-
-    with tempfile.TemporaryDirectory(dir=os.getcwd()) as workdir:
-        image = f"{workdir}/image.raw"
-        mountpoint = f"{workdir}/mnt"
-
-        subprocess.run(["truncate", "--size", str(int(size * 1.1)), image], check=True)
-
-        partition_table = "label: mbr\nbootable, type=83"
-        subprocess.run(["sfdisk", "-q", image], input=partition_table, encoding='utf-8', check=True)
-
-        with loop_device(image) as loop:
-            subprocess.run(["mkfs.ext4", "-d", tree, f"{loop}p1"], check=True)
-
-            # grub2-mkconfig and grub2-install only seem to work reliably when
-            # called from a chroot
-            with mount_image(f"{loop}p1", mountpoint):
-                subprocess.run(["chroot", mountpoint, "grub2-mkconfig", "-o", "/boot/grub2/grub.cfg"], check=True)
-                subprocess.run(["chroot", mountpoint, "grub2-install", "--no-floppy", "--target", "i386-pc", loop], check=True)
-
-        subprocess.run(["qemu-img", "convert", "-O" "qcow2", "-c", image, target], check=True)
-
-if __name__ == '__main__':
-    args = json.load(sys.stdin)
-
-    try:
-        r = main(args["tree"], args["options"])
-    except CalledProcessError as e:
-        print(e, file=sys.stderr)
-        r = 1
-
-    sys.exit(r)