and we need to enforce the root FS UUID. i think.

this should work. probably.

_base.py

@@ -1,4 +1,5 @@
 import hashlib
+import json
 import os
 import pathlib
 import shutil
@@ -43,6 +44,7 @@ class BaseUpdater(object):
         self.do_update = False
         self.force_update = False
         self.iso_url = None
+        self.boot_uuid = None
         self.hash_type = hash_type
         self.dest_iso = os.path.join(self.dest_dir, self.dest_file)
         self.dest_ver = os.path.join(self.dest_dir, self.ver_file)
@@ -108,7 +110,30 @@ class BaseUpdater(object):
             return(False)
         return(True)
 
+    def getUUID(self):
+        disk_cmd = subprocess.run(['findmnt',
+                                   '-T', '/boot',
+                                   '--json'],
+                                  stdout = subprocess.PIPE,
+                                  stderr = subprocess.PIPE)
+        if (disk_cmd.returncode != 0) or disk_cmd.stderr.decode('utf-8').strip() != '':
+            raise RuntimeError('Could not get disk UUID: {0}'.format(disk_cmd.stderr.decode('utf-8')))
+        disk_dict = json.loads(disk_cmd.stdout.decode('utf-8'))
+        disk_dev = disk_dict['filesystems']['source']
+        info_cmd = subprocess.run(['blkid',
+                                   '-o', 'export',
+                                   disk_dev],
+                                  stdout = subprocess.PIPE,
+                                  stderr = subprocess.PIPE)
+        if (info_cmd.returncode != 0) or info_cmd.stderr.decode('utf-8').strip() != '':
+            raise RuntimeError('Could not get disk UUID: {0}'.format(info_cmd.stderr.decode('utf-8')))
+        info_dict = {i.split('=', 1)[0].lower():i.split('=', 1)[1]
+                     for i in info_cmd.stdout.decode('utf-8').splitlines()}
+        self.boot_uuid = info_dict.get('uuid')
+        return(None)
+
     def grub(self):
+        self.getUUID()
         import jinja2
         loader = jinja2.FileSystemLoader(searchpath = self._tpl_dir)
         tplenv = jinja2.Environment(loader = loader)
@@ -117,7 +142,8 @@ class BaseUpdater(object):
             fh.write(tpl.render(iso_path = os.path.abspath(
                                     os.path.expanduser(
                                         os.path.join(self.grub_iso_dir,
-                                                     self.dest_file)))))
+                                                     self.dest_file))),
+                                disk_uuid = self.boot_uuid))
         os.chmod(self.grub_cfg, 0o0755)
         cmd = subprocess.run(['grub-mkconfig',
                               '-o', '{0}/grub/grub.cfg'.format(self.boot_dir)],