diff --git a/iridium_installer/backend/os_install.py b/iridium_installer/backend/os_install.py
index 3902674..e824b9e 100644
--- a/iridium_installer/backend/os_install.py
+++ b/iridium_installer/backend/os_install.py
@@ -1,28 +1,30 @@
-import subprocess
 import logging
 import os
+import subprocess
 import sys
 from contextlib import contextmanager
 
 logger = logging.getLogger(__name__)
 
+
 class CommandResult:
     def __init__(self, stdout, stderr, returncode):
         self.stdout = stdout
         self.stderr = stderr
         self.returncode = returncode
 
+
 def run_command(cmd, check=True):
     logger.info(f"Running command: {' '.join(cmd)}")
-    
+
     process = subprocess.Popen(
         cmd,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
         text=True,
-        bufsize=1  # Line buffered
+        bufsize=1,  # Line buffered
     )
-    
+
     stdout_lines = []
     stderr_lines = []
 
@@ -35,25 +37,33 @@ def run_command(cmd, check=True):
                 line_list.append(line)
 
     import threading
-    t1 = threading.Thread(target=read_stream, args=(process.stdout, stdout_lines, logger.info))
-    t2 = threading.Thread(target=read_stream, args=(process.stderr, stderr_lines, logger.error))
-    
+
+    t1 = threading.Thread(
+        target=read_stream, args=(process.stdout, stdout_lines, logger.info)
+    )
+    t2 = threading.Thread(
+        target=read_stream, args=(process.stderr, stderr_lines, logger.error)
+    )
+
     t1.start()
     t2.start()
-    
+
     t1.join()
     t2.join()
-    
+
     returncode = process.wait()
-    
+
     stdout_str = "".join(stdout_lines)
     stderr_str = "".join(stderr_lines)
-    
+
     if check and returncode != 0:
-        raise subprocess.CalledProcessError(returncode, cmd, output=stdout_str, stderr=stderr_str)
-        
+        raise subprocess.CalledProcessError(
+            returncode, cmd, output=stdout_str, stderr=stderr_str
+        )
+
     return CommandResult(stdout_str, stderr_str, returncode)
 
+
 @contextmanager
 def mount_pseudo_fs(mount_root):
     """
@@ -62,7 +72,7 @@ def mount_pseudo_fs(mount_root):
     logger.info(f"Mounting pseudo-filesystems to {mount_root}...")
     mounts = ["dev", "proc", "sys"]
     mounted_paths = []
-    
+
     try:
         for fs in mounts:
             target = os.path.join(mount_root, fs)
@@ -78,12 +88,13 @@ def mount_pseudo_fs(mount_root):
             except Exception as e:
                 logger.warning(f"Failed to unmount {path}: {e}")
 
-def install_minimal_os(mount_root, releasever="41"):
+
+def install_minimal_os(mount_root, releasever="43"):
     """
     Installs minimal Fedora packages to mount_root.
     """
     logger.info(f"Installing minimal Fedora {releasever} to {mount_root}...")
-    
+
     packages = [
         "basesystem",
         "bash",
@@ -96,29 +107,32 @@ def install_minimal_os(mount_root, releasever="41"):
         "efibootmgr",
         "passwd",
         "rootfiles",
-        "vim-minimal"
+        "vim-minimal",
     ]
-    
+
     cmd = [
-        "dnf", "install", "-y",
+        "dnf",
+        "install",
+        "-y",
         f"--installroot={mount_root}",
         f"--releasever={releasever}",
         "--use-host-config",
         "--setopt=install_weak_deps=False",
-        "--nodocs"
+        "--nodocs",
     ] + packages
-    
+
     with mount_pseudo_fs(mount_root):
         run_command(cmd)
-    
+
     logger.info("Base system installation complete.")
 
+
 def configure_system(mount_root, partition_info):
     """
     Basic configuration: fstab and grub.
     """
     logger.info("Configuring system...")
-    
+
     # 1. Generate fstab
     def get_uuid(dev):
         res = run_command(["blkid", "-s", "UUID", "-o", "value", dev])
@@ -126,7 +140,7 @@ def configure_system(mount_root, partition_info):
 
     root_uuid = get_uuid(partition_info["root"])
     efi_uuid = get_uuid(partition_info["efi"])
-    
+
     swap_entry = ""
     if partition_info.get("swap"):
         swap_uuid = get_uuid(partition_info["swap"])
@@ -140,11 +154,17 @@ UUID={efi_uuid} /boot/efi vfat defaults 0 2
     os.makedirs(os.path.join(mount_root, "etc"), exist_ok=True)
     with open(os.path.join(mount_root, "etc/fstab"), "w") as f:
         f.write(fstab_content)
-    
+
     # 2. Configure GRUB
     with mount_pseudo_fs(mount_root):
         # grub2-mkconfig -o /boot/grub2/grub.cfg
-        chroot_cmd = ["chroot", mount_root, "grub2-mkconfig", "-o", "/boot/grub2/grub.cfg"]
+        chroot_cmd = [
+            "chroot",
+            mount_root,
+            "grub2-mkconfig",
+            "-o",
+            "/boot/grub2/grub.cfg",
+        ]
         run_command(chroot_cmd)
 
     logger.info("System configuration complete.")