fix build (#865)

Author: creatorcary

scale_build/update_image.py

@@ -40,7 +40,10 @@ def build_update_image_impl():
 
             # These files will be overwritten, so we should make sure that new build does not have any entities that
             # are not in our reference files.
-            for reference_file, diff in compare_reference_files(cut_nonexistent_user_group_membership=True):
+            for reference_file, diff in compare_reference_files(
+                cut_nonexistent_user_group_membership=True,
+                default_homedir='/var/empty'
+            ):
                 if any(line.startswith('+') for line in diff):
                     raise CallError(
                         f'Reference file {reference_file!r} has new lines in newly installed system.\n'

scale_build/utils/reference_files.py

@@ -6,7 +6,12 @@
 from .paths import REFERENCE_FILES_DIR, REFERENCE_FILES, CHROOT_BASEDIR
 
 
-def compare_reference_files(cut_nonexistent_user_group_membership=False):
+def compare_reference_files(cut_nonexistent_user_group_membership: bool = False, default_homedir: str | None = None):
+    """Diff /conf/reference-files/etc/group|passwd with the respective files in chroot.
+
+    :param cut_nonexistent_user_group_membership:
+    :param default_homedir: A home directory to replace Debian's default `/nonexistent` before running the diff.
+    """
     for reference_file in REFERENCE_FILES:
         with open(os.path.join(REFERENCE_FILES_DIR, reference_file)) as f:
             reference = f.readlines()
@@ -29,6 +34,9 @@ def compare_reference_files(cut_nonexistent_user_group_membership=False):
         with open(os.path.join(CHROOT_BASEDIR, reference_file)) as f:
             real = f.readlines()
 
+        if default_homedir and reference_file == 'etc/passwd':
+            real = [line.replace('/nonexistent', default_homedir) for line in real]
+
         diff = list(difflib.unified_diff(reference, real))
 
         yield reference_file, diff[3:]