Continue guest-update rollback after individual restore failures

dev/guest-update.py

@@ -179,17 +179,30 @@ def apply_bundle(bundle, root=Path('/'), *, execute=False):
         for name, (data, mode) in payload.items():
             atomic_write(checked_path(root, name), data, mode)
             changed.append(name)
-    except BaseException:
+    except BaseException as apply_error:
+        rollback_errors = {}
         for name in reversed(changed):
-            dest = checked_path(root, name)
-            original = records[name]
-            if 'symlink' in original:
-                dest.unlink()
-                dest.symlink_to(original['symlink'])
-            elif original['existed']:
-                atomic_write(dest, (backup / name).read_bytes(), original['mode'])
-            else:
-                dest.unlink()
+            try:
+                dest = checked_path(root, name)
+                original = records[name]
+                if 'symlink' in original:
+                    dest.unlink()
+                    dest.symlink_to(original['symlink'])
+                elif original['existed']:
+                    atomic_write(dest, (backup / name).read_bytes(), original['mode'])
+                else:
+                    dest.unlink(missing_ok=True)
+            except BaseException as restore_error:
+                # A full/unavailable filesystem may prevent one restoration
+                # while unlinking independently created files still succeeds.
+                rollback_errors[name] = f'{type(restore_error).__name__}: {restore_error}'
+        if rollback_errors:
+            report = ('Hydra OS update: rollback incomplete; the runtime may contain mixed versions.\n'
+                      f'Retained backup: {backup}\n'
+                      'Manual recovery records: ' + str(backup / 'backup.json') + '\n' +
+                      '\n'.join(f'  {name}: {error}' for name, error in rollback_errors.items()))
+            apply_error.add_note(report)
+            print(report, file=sys.stderr)
         raise
     result.update(applied=True, backup=str(backup))
     return result