Support writing loader.conf when using unified kernel

kernelstub/application.py

@@ -335,12 +335,14 @@ def main(self, args): # Do the thing
             installer.setup_unified_kernel(
                 kopts,
                 old=False,
+                overwrite=force,
                 simulate=no_run
             )
             try:
                 installer.setup_unified_kernel(
                     kopts,
                     old=True,
+                    overwrite=force,
                     simulate=no_run)
             except Exception as e:
                 log.debug('Couldn\'t back up old kernel. \nThis might just mean ' +

kernelstub/installer.py

@@ -58,7 +58,7 @@ def __init__(self, nvram, opsys, drive):
         if not os.path.exists(self.entry_dir):
             os.makedirs(self.entry_dir)
 
-    def setup_unified_kernel(self, kernel_opts, old=False, simulate=False):
+    def setup_unified_kernel(self, kernel_opts, old=False, overwrite=False, simulate=False):
         if old:
             suffix = 'previous'
             kernel_path = self.opsys.old_kernel_path
@@ -124,6 +124,18 @@ def setup_unified_kernel(self, kernel_opts, old=False, simulate=False):
             simulate=simulate
         )
 
+        if not overwrite and not simulate:
+            if not os.path.exists('%s/loader.conf' % self.loader_dir):
+                overwrite = True
+
+        if overwrite and not old and not simulate:
+            self.ensure_dir(self.loader_dir)
+            with open(
+                '%s/loader.conf' % self.loader_dir, mode='w') as loader:
+
+                default_line = 'default %s\n' % kernel_efi_name
+                loader.write(default_line)
+
     def backup_old(self, kernel_opts, setup_loader=False, simulate=False):
         self.log.info('Backing up old kernel')