diff --git a/master.py b/master.py
index 768f050..114e354 100755
--- a/master.py
+++ b/master.py
@@ -10,6 +10,7 @@ import os
 import sys
 import yaml
 import slugify
+import readline
 from PIL import Image
 
 
@@ -27,23 +28,11 @@ Type a category name to see a list of elements. Available categories are:
 For each category, an argument can be specified:
 * 'clear' will remove all entries in the category (destroys a lot of data!)
 * 'update' will update from the model in app/data/, when applicable
-  (currently available on: forums)
-
-Type 'create-groups-and-privs' to recreate all groups and privileges to the
-default. This function generates a minimal set of groups and members to prepare
-the database.
-1. Deletes all groups
-2. Creates groups 'Administrateur', 'Modérateur', 'Développeur', 'Rédacteur',
-   'Responsable Communauté', 'Partenaire', 'Compte communautaire', 'Robot', and
-   'Membre de CreativeCalc'
-3. Grants privileges related to these groups
-4. Recreates common accounts: 'Planète Casio' (community account) and 'GLaDOS'
-   (robot)
+  (currently available on: forums, groups)
 
+Type 'create-common-accounts' to recreate 'Planète Casio' and 'GLaDOS'
 Type 'add-group <member> #<group-id>' to add a new member to a group.
-
 Type 'create-trophies' to reset trophies and titles and their icons.
-
 Type 'enable-user' to enable a email-disabled account.
 """
 
@@ -70,6 +59,10 @@ def groups(*args):
         print("Removed all groups.")
         return
 
+    if args == ("update",):
+        update_groups()
+        return
+
     for g in Group.query.all():
          print(f"#{g.id}  {g.name}")
 
@@ -114,37 +107,56 @@ def forums(*args):
 #  Creation and edition
 #
 
-def create_groups_and_privs():
-    # Clean up groups
-    groups("clear")
+def update_groups():
+    existing = Group.query.all()
 
-    # Create base groups
     gr = []
     with open(os.path.join(app.root_path, "data", "groups.yaml")) as fp:
         gr = yaml.safe_load(fp.read())
 
-    for g in gr:
-        g["obj"] = Group(g["name"], g["css"], g["descr"])
-        db.session.add(g["obj"])
-    db.session.commit()
+    for group_info in gr:
+        name   = group_info["name"]
+        css    = group_info.get("css", "")
+        descr  = group_info.get("descr", "")
+        privs  = group_info.get("privs", "").split()
 
-    for g in gr:
-        for priv in g.get("privs", "").split():
-            db.session.add(GroupPrivilege(g["obj"], priv))
-    db.session.commit()
+        g = Group.query.filter_by(name=name).first()
 
-    print(f"Created {len(gr)} groups.")
+        # Update an existing group
+        if g is not None:
+            changes = (g.css != css) or (g.description != descr) or \
+                (set(g.privs()) != set(privs))
+            g.css = css
+            g.description = descr
 
-    # Clean up test members
+            for gpriv in GroupPrivilege.query.filter_by(gid=g.id):
+                db.session.delete(gpriv)
+            for priv in privs:
+                db.session.add(GroupPrivilege(g, priv))
+
+            if changes:
+                db.session.add(g)
+                print(f"[group] Updated {g.name}")
+        # Create a new one
+        else:
+            g = Group(name, css, descr)
+            db.session.add(g)
+            db.session.commit()
+
+            for priv in privs:
+                db.session.add(GroupPrivilege(g, priv))
+
+            print(f"[group] Created {g.name}")
+
+
+def create_common_accounts():
+    # Clean up common accounts
     for name in "PlanèteCasio GLaDOS".split():
         m = Member.query.filter_by(name=name).first()
         if m is not None:
             m.delete()
 
-    print("Removed test members.")
-
-    # Create template members
-
+    # Recreate theme
     def addgroup(member, group):
         g = Group.query.filter_by(name=group).first()
         if g is not None:
@@ -167,8 +179,6 @@ def create_groups_and_privs():
 
     db.session.commit()
 
-    print(f"Created 2 test members with some privileges.")
-
 
 def create_trophies():
     # Clean up trophies
@@ -315,7 +325,7 @@ commands = {
     "trophies":                 trophies,
     "trophy-members":           trophy_members,
     "forums":                   forums,
-    "create-groups-and-privs":  create_groups_and_privs,
+    "create-common-accounts":   create_common_accounts,
     "create-trophies":          create_trophies,
     "create-trophies-icons":    create_trophies_icons,
     "add-group":                add_group,
@@ -338,8 +348,7 @@ else:
 
     while True:
         try:
-            print("@> ", end="")
-            cmd = input().split()
+            cmd = input("@> ").split()
         except EOFError:
             sys.exit(0)