diff --git a/gvaldap/ldapentities/models.py b/gvaldap/ldapentities/models.py
index f4ee071..ef1d390 100644
--- a/gvaldap/ldapentities/models.py
+++ b/gvaldap/ldapentities/models.py
@@ -23,6 +23,7 @@ class LdapGroup(ldapmodels.Model):
     # posixGroup attributes
     gid = IntegerField(db_column='gidNumber', unique=True)
     name = CharField(db_column='cn', max_length=200, primary_key=True)
+    description = CharField(db_column='description')
     members = ListField(db_column='memberUid', blank=True)
 
     def __str__(self):
diff --git a/gvaldap/osusers/models.py b/gvaldap/osusers/models.py
index e1c641f..e69de29 100644
--- a/gvaldap/osusers/models.py
+++ b/gvaldap/osusers/models.py
@@ -1,42 +0,0 @@
-from django.db import models
-from django.utils.encoding import python_2_unicode_compatible
-from django.utils.translation import ugettext as _
-
-from model_utils.models import TimeStampedModel
-
-
-@python_2_unicode_compatible
-class Group(TimeStampedModel, models.Model):
-    groupname = models.CharField(
-        _('Group name'), max_length=16, unique=True)
-    gid = models.PositiveSmallIntegerField(
-        _('Group ID'), unique=True, primary_key=True)
-    descr = models.TextField(_('Description'), blank=True)
-    passwd = models.CharField(
-        _('Group password'), max_length=128, blank=True)
-
-    class Meta:
-        verbose_name = _('Group')
-        verbose_name_plural = _('Groups')
-
-    def __str__(self):
-        return '{0} ({1})'.format(self.groupname, self.gid)
-
-
-@python_2_unicode_compatible
-class User(TimeStampedModel, models.Model):
-    username = models.CharField(
-        _('User name'), max_length=64, unique=True)
-    uid = models.PositiveSmallIntegerField(
-        _('User ID'), unique=True, primary_key=True)
-    group = models.ForeignKey(Group, verbose_name=_('Group'))
-    gecos = models.CharField(_('Gecos field'), max_length=128, blank=True)
-    homedir = models.CharField(_('Home directory'), max_length=256)
-    shell = models.CharField(_('Login shell'), max_length=64)
-
-    class Meta:
-        verbose_name = _('User')
-        verbose_name_plural = _('Users')
-
-    def __str__(self):
-        return '{0} ({1})'.format(self.username, self.uid)
diff --git a/gvaldap/osusers/tasks.py b/gvaldap/osusers/tasks.py
index f0b6fbc..b1be4c1 100644
--- a/gvaldap/osusers/tasks.py
+++ b/gvaldap/osusers/tasks.py
@@ -1,28 +1,130 @@
 from __future__ import absolute_import
 
+from django.core.exceptions import ObjectDoesNotExist
 from celery import shared_task
+from celery.utils.log import get_task_logger
+from celery.exceptions import Reject
 from ldapentities.models import (
     LdapGroup,
     LdapUser,
 )
 
 
+_logger = get_task_logger(__name__)
+
+
 @shared_task
-def create_ldap_group(group):
-    ldapgroup = LdapGroup(gid=group.gid, name=group.groupname)
+def create_ldap_group(groupname, gid, descr):
+    try:
+        ldapgroup = LdapGroup.objects.get(name=groupname)
+        _logger.info(
+            'ldap group with dn {0} already exists'.format(ldapgroup.dn)
+        )
+        ldapgroup.gid = gid
+    except LdapGroup.DoesNotExist:
+        ldapgroup = LdapGroup(gid=gid, name=groupname)
+    ldapgroup.description = descr
     ldapgroup.save()
     return ldapgroup.dn
 
 
 @shared_task
-def create_ldap_user(user, password):
-    ldapuser = LdapUser(
-        uid=user.uid, group=user.group.gid, gecos=user.gecos,
-        home_directory=user.homedir, login_shell=user.shell,
-        username=user.username, common_name=user.username)
-    ldapuser.set_password(password)
-    ldapgroup = LdapGroup.objects.get(gid=ldapuser.group)
-    ldapgroup.members.append(ldapuser.username)
-    ldapgroup.save()
+def create_ldap_user(username, uid, gid, gecos, homedir, shell, password):
+    try:
+        ldapuser = LdapUser.objects.get(username=username)
+        _logger.info(
+            'ldap user with dn {0} already exists'.format(ldapuser.dn)
+        )
+    except LdapUser.DoesNotExist:
+        ldapuser = LdapUser(username=username)
+    try:
+        ldapgroup = LdapGroup.objects.get(gid=gid)
+    except ObjectDoesNotExist as exc:
+        _logger.info('ldap group with gid {0} does not exist')
+        raise Reject(exc, requeue=False)
+    ldapuser.uid = uid
+    ldapuser.group = gid
+    ldapuser.gecos = gecos
+    ldapuser.home_directory = homedir
+    ldapuser.login_shell = shell
+    ldapuser.username = username
+    ldapuser.common_name = username
+    if password is not None:
+        ldapuser.set_password(password)
+    if ldapuser.username in ldapgroup.members:
+        _logger.info('user {0} is already member of {1}'.format(
+            ldapuser.username, ldapgroup.dn)
+        )
+    else:
+        ldapgroup.members.append(ldapuser.username)
+        ldapgroup.save()
     ldapuser.save()
     return ldapuser.dn
+
+
+@shared_task(bind=True)
+def add_ldap_user_to_group(self, username, groupname):
+    try:
+        ldapgroup = LdapGroup.objects.get(name=groupname)
+        ldapuser = LdapUser.objects.get(username=username)
+    except LdapGroup.DoesNotExist:
+        _logger.error('ldap group {0} does not exist'.format(groupname))
+    except LdapUser.DoesNotExist as exc:
+        _logger.error('ldap user {0} does not exist'.format(username))
+        self.retry(exc=exc, time_limit=5)
+    else:
+        if not ldapuser.username in ldapgroup.members:
+            ldapgroup.members.append(ldapuser.username)
+            ldapgroup.save()
+        else:
+            _logger.info('ldap user {0} is already in group {1}'.format(
+                ldapuser.username, ldapgroup.dn)
+            )
+
+
+@shared_task
+def remove_ldap_user_from_group(username, groupname):
+    ldapgroup = LdapGroup.objects.get(name=groupname)
+    ldapuser = LdapUser.objects.get(username=username)
+    if ldapuser.username in ldapgroup.members:
+        ldapgroup.members.remove(ldapuser.username)
+    ldapgroup.save()
+
+
+@shared_task
+def delete_ldap_user(username):
+    try:
+        ldapuser = LdapUser.objects.get(username=username)
+    except LdapUser.DoesNotExist:
+        _logger.info('there is no ldap user with uid {0}'.format(
+            username)
+        )
+    else:
+        try:
+            ldapgroup = LdapGroup.objects.get(gid=ldapuser.group)
+        except LdapGroup.DoesNotExist:
+            _logger.info('group {0} for user {1} does not exist'.format(
+                ldapuser.group, ldapuser.username)
+            )
+        else:
+            if ldapuser.username in ldapgroup.members:
+                ldapgroup.members.remove(ldapuser.username)
+                ldapgroup.save()
+        ldapuser.delete()
+
+
+@shared_task
+def delete_ldap_group_if_empty(groupname):
+    try:
+        ldapgroup = LdapGroup.objects.get(name=groupname)
+    except LdapGroup.DoesNotExist:
+        _logger.info('ldap group with name {0} does not exist'.format(
+            groupname)
+        )
+    else:
+        if len(ldapgroup.members) == 0:
+            ldapgroup.delete()
+        else:
+            _logger.info('ldap group {0} still has {1} members'.format(
+                ldapgroup.dn, len(ldapgroup.members))
+            )