bootloader: use grub2-mkconfig for EFI boot entry generation

This patch simplifies the EFI GRUB configuration generation by replacing the manual config
file writing with a `grub2-mkconfig` command. By doing so, we avoid direct file handling
and path resolution issues, leveraging `grub2-mkconfig` to set up the correct paths and UUIDs.

Additionally, this change enables OS Prober in `grub.cfg` generation by default, ensuring that
other operating systems are detected and added to the boot menu automatically. This is particularly
useful for multi-boot environments, as it allows the system to recognize existing OS installations
without additional configuration.

pyanaconda/modules/storage/bootloader/efi.py

@@ -178,27 +178,10 @@ def efi_config_file(self):
         return "%s/%s" % (self.efi_config_dir, self._config_file)
 
     def write_config(self):
-        config_path = "%s%s" % (conf.target.system_root, self.efi_config_file)
-
-        with open(config_path, "w") as fd:
-            grub_dir = self.config_dir
-            if self.stage2_device.format.type != "btrfs":
-                fs_uuid = self.stage2_device.format.uuid
-            else:
-                fs_uuid = self.stage2_device.format.vol_uuid
-
-            if fs_uuid is None:
-                raise BootLoaderError("Could not get stage2 filesystem UUID")
-
-            grub_dir = util.execWithCapture("grub2-mkrelpath", [grub_dir],
-                                            root=conf.target.system_root)
-            if not grub_dir:
-                raise BootLoaderError("Could not get GRUB directory path")
-
-            fd.write("search --no-floppy --fs-uuid --set=dev %s\n" % fs_uuid)
-            fd.write("set prefix=($dev)%s\n" % grub_dir)
-            fd.write("export $prefix\n")
-            fd.write("configfile $prefix/grub.cfg\n")
+        """ Run grub2-mkconfig to generate the EFI grub.cfg file for the new system. """
+        ret = util.execWithRedirect("grub2-mkconfig", ["-o", self.efi_config_file], root=conf.target.system_root)
+        if ret != 0:
+            raise BootLoaderError("failed to generate EFI grub.cfg file.")
 
         super().write_config()
 

pyanaconda/modules/storage/bootloader/grub2.py

@@ -253,6 +253,7 @@ def write_device_map(self):
     def write_defaults(self):
         defaults_file = "%s%s" % (conf.target.system_root, self.defaults_file)
         defaults = open(defaults_file, "w+")
+        defaults.write("GRUB_DISABLE_OS_PROBER=false\n")
         defaults.write("GRUB_TIMEOUT=%d\n" % self.timeout)
         defaults.write("GRUB_DISTRIBUTOR=\"$(sed 's, release .*$,,g' /etc/system-release)\"\n")
         defaults.write("GRUB_DEFAULT=saved\n")