slightly comical way of getting the created user added to the right groups

snapcraft.yaml

@@ -50,6 +50,14 @@ parts:
       'bin/started': usr/bin/started
     prime:
       - usr/bin
+  users-and-groups:
+    plugin: dump
+    build-packages:
+      - user-setup
+    prepare: |
+      echo "get passwd/user-default-groups" | \
+        debconf-communicate user-setup |
+        cut -d ' ' -f 2- > users-and-groups
   probert:
     plugin: python
     build-packages: [python-setuptools, libnl-3-dev, libnl-genl-3-dev, libnl-route-3-dev]

subiquity/curtin.py

@@ -76,12 +76,17 @@ POST_INSTALL_CONFIG = {
 
 
 def curtin_userinfo_to_config(userinfo):
+    users_and_groups_path = os.path.join(os.environ.get("SNAP", "/does-not-exist"), "users-and-groups")
+    if os.path.exists(users_and_groups_path):
+        groups = open(users_and_groups_path).read().split()
+    else:
+        groups = ['admin']
     user = {
         'name': userinfo['username'],
         'gecos': userinfo['realname'],
         'passwd': userinfo['password'],
         'shell': '/bin/bash',
-        'groups': 'admin',
+        'groups': groups,
         'lock-passwd': False,
         }
     if 'ssh_import_id' in userinfo: