diff --git a/versions.toml b/versions.toml
new file mode 100644
index 0000000..8aeb930
--- /dev/null
+++ b/versions.toml
@@ -0,0 +1,2 @@
+rust = "1.91.1"
+rustup = "1.28.2"
diff --git a/x.py b/x.py
index a450b7a..31dd00e 100755
--- a/x.py
+++ b/x.py
@@ -1,15 +1,27 @@
 #!/usr/bin/env python3
 
+import argparse
 from collections import namedtuple
 from urllib import request
 import os
 import subprocess
-import sys
+import tomllib
 
-rustup_version = "1.28.2"
+def load_versions():
+    with open("versions.toml", "rb") as f:
+        versions = tomllib.load(f)
+        rust_version = versions['rust']
+        rustup_version = versions['rustup']
+    return rust_version, rustup_version
 
+def write_versions(rust_version, rustup_version):
+    with open("versions.toml", "w") as f:
+        f.write(f'rust = "{rust_version}"\n')
+        f.write(f'rustup = "{rustup_version}"\n')
+
+rust_version, rustup_version = load_versions()
 Channel = namedtuple("Channel", ["name", "rust_version"])
-stable = Channel("stable", "1.91.1")
+stable = Channel("stable", rust_version)
 nightly = Channel("nightly", "nightly")
 supported_channels = [
     stable,
@@ -366,22 +378,31 @@ def generate_stackbrew_library():
 
     print(library)
 
-def usage():
-    print(f"Usage: {sys.argv[0]} update|generate-stackbrew-library")
-    sys.exit(1)
-
 if __name__ == "__main__":
-    if len(sys.argv) != 2:
-        usage()
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(dest='subcommand', required=True)
+
+    update_parser = subparsers.add_parser('update')
+    update_parser.add_argument('--rust', metavar='VERSION', dest='rust', action='store')
+    update_parser.add_argument('--rustup', metavar='VERSION', dest='rustup', action='store')
+
+    generate_stackbrew_library_parser = subparsers.add_parser('generate-stackbrew-library')
+
+    args = parser.parse_args()
+    if args.subcommand == "update":
+        if args.rust:
+            rust_version = args.rust
+            stable = Channel("stable", rust_version)
+            write_versions(rust_version, rustup_version)
+
+        if args.rustup:
+            rustup_version = args.rustup
+            write_versions(rust_version, rustup_version)
 
-    task = sys.argv[1]
-    if task == "update":
         update_debian()
         update_alpine()
         update_ci()
         update_mirror_stable_ci()
-        update_nightly_ci() 
-    elif task == "generate-stackbrew-library":
+        update_nightly_ci()
+    elif args.subcommand == "generate-stackbrew-library":
         generate_stackbrew_library()
-    else:
-        usage()