diff --git a/terraform/scripts/stage_talos_image.py b/terraform/scripts/stage_talos_image.py
index 4f33377..dada3b3 100644
--- a/terraform/scripts/stage_talos_image.py
+++ b/terraform/scripts/stage_talos_image.py
@@ -4,10 +4,10 @@ import gzip
 import json
 import os
 import shutil
+import ssl
 import subprocess
 import sys
 import tempfile
-import ssl
 import time
 import urllib.error
 import urllib.parse
@@ -79,41 +79,66 @@ def wait_for_task(base_url, token, node, upid):
     raise RuntimeError("timed out waiting for ISO download task to finish")
 
 
+def detect_proxmox_iso_dir(storage):
+    candidates = [
+        Path("/var/lib/vz/template/iso"),
+        Path("C:/var/lib/vz/template/iso"),
+    ]
+    for candidate in candidates:
+        if candidate.exists():
+            return candidate
+    raise RuntimeError(f"unable to find ISO directory for storage '{storage}'")
+
+
+
 def build_custom_iso(base_url, token, node, storage, source_filename, output_filename, network_config_path):
-    storage_path = f"/var/lib/vz/template/iso/{source_filename}"
-    output_path = f"/var/lib/vz/template/iso/{output_filename}"
+    iso_dir = detect_proxmox_iso_dir(storage)
+    storage_path = iso_dir / source_filename
+    output_path = iso_dir / output_filename
     network_config = Path(network_config_path).read_text(encoding="utf-8").strip()
     installer_meta = base64.b64encode(gzip.compress(f"0xa={network_config}".encode("utf-8"), compresslevel=9)).decode("ascii")
 
-    if shutil.which("docker") is None:
-        raise RuntimeError("docker is required to build Talos ISO with embedded META")
+    xorriso = shutil.which("xorriso")
+    if xorriso is None:
+        raise RuntimeError("xorriso is required to build Talos ISO with embedded META")
 
     with tempfile.TemporaryDirectory() as temp_dir:
         temp_path = Path(temp_dir)
-        script_path = temp_path / "build.sh"
-        script_path.write_text(
-            "#!/bin/sh\n"
-            "set -eu\n"
-            "apk add --no-cache xorriso >/dev/null\n"
-            "cp /input/source.iso /work/source.iso\n"
-            "xorriso -indev /work/source.iso -outdev /output/result.iso -boot_image any replay \\\n"
-            f"  -append_partition 2 0x0 /dev/null \\\n"
-            f"  -boot_image any keep \\\n"
-            f"  -map /input/cmdline /cmdline\n",
-            encoding="utf-8",
-        )
-        cmdline_path = temp_path / "cmdline"
-        cmdline_path.write_text(f"talos.environment=INSTALLER_META_BASE64={installer_meta}\n", encoding="utf-8")
+        extract_dir = temp_path / "extract"
+        extract_dir.mkdir()
+        output_tmp = temp_path / output_filename
+
+        subprocess.run([xorriso, "-osirrox", "on", "-indev", str(storage_path), "-extract", "/", str(extract_dir)], check=True)
+
+        isolinux_cfg = extract_dir / "isolinux" / "isolinux.cfg"
+        grub_cfg = extract_dir / "boot" / "grub" / "grub.cfg"
+        append = f" talos.environment=INSTALLER_META_BASE64={installer_meta}"
+        for cfg in (isolinux_cfg, grub_cfg):
+            if cfg.exists():
+                text = cfg.read_text(encoding="utf-8")
+                text = text.replace("---", f"{append} ---", 1)
+                cfg.write_text(text, encoding="utf-8")
+
         subprocess.run([
-            "docker", "run", "--rm",
-            "-v", f"{script_path}:/input/build.sh:ro",
-            "-v", f"{cmdline_path}:/input/cmdline:ro",
-            "-v", f"{Path(storage_path).resolve()}:/input/source.iso:ro",
-            "-v", f"{temp_path}:/work",
-            "-v", f"{Path(output_path).resolve().parent}:/output",
-            "alpine:3.20", "sh", "/input/build.sh",
+            xorriso,
+            "-as", "mkisofs",
+            "-o", str(output_tmp),
+            "-isohybrid-mbr", str(extract_dir / "isolinux" / "isohdpfx.bin"),
+            "-c", "isolinux/boot.cat",
+            "-b", "isolinux/isolinux.bin",
+            "-no-emul-boot",
+            "-boot-load-size", "4",
+            "-boot-info-table",
+            "-eltorito-alt-boot",
+            "-e", "EFI/BOOT/BOOTX64.EFI",
+            "-no-emul-boot",
+            "-isohybrid-gpt-basdat",
+            "-V", "TALOS",
+            str(extract_dir),
         ], check=True)
 
+        shutil.copyfile(output_tmp, output_path)
+
 
 def main():
     parser = argparse.ArgumentParser()