diff --git a/lumi2/ldap.py b/lumi2/ldap.py
index 8e097e9..c8373f1 100644
--- a/lumi2/ldap.py
+++ b/lumi2/ldap.py
@@ -13,7 +13,7 @@ from base64 import b64decode, b64encode
 from io import BytesIO
 
 from flask import current_app
-from ldap3 import Connection, Server, ALL, Reader, Writer, ObjectDef
+from ldap3 import Connection, Server, ALL, Reader, Writer, ObjectDef, MODIFY_REPLACE
 from PIL import Image
 
 from lumi2.usermodel import User, Group
@@ -712,6 +712,53 @@ def create_user(connection: Connection, user: User) -> None:
     connection.add(user.get_dn(), "inetOrgPerson", attributes)
 
 
+def update_user(connection: Connection, user: User) -> None:
+    """Updates the LDAP entry for the specified User.
+
+    All attributes of the user's entry on the LDAP server are overwritten using
+    the User object's instance attributes.
+
+    Parameters
+    ----------
+    connection : ldap3.Connection
+        Bound Connection object to an LDAP server.
+    user : lumi2.usermodel.User
+        User object whose LDAP entry will be updated.
+
+    Raises
+    ------
+    TypeError
+        If user is not of type User.
+    EntryNotFoundException
+        If no entry for the specified user's uid (username) exists in the LDAP
+        server's DIT.
+    """
+
+    _assert_is_valid_connection(connection)
+    if not isinstance(user, User):
+        raise TypeError(f"Expected a User but got: '{type(user)}'.")
+    user_dn = user.get_dn()
+    if not user_exists(connection, user_dn):
+        raise EntryNotFoundException(
+            f"Failed to update user '{user.username}': no entry exists for " \
+            f"'{user_dn}'."
+        )
+
+    new_picture_bytes = BytesIO()
+    user.picture.save(new_picture_bytes, format="jpeg")
+
+    new_attributes = {
+        "userPassword": [(MODIFY_REPLACE, ["{SHA512}" + user.password_hash])],
+        "mail":         [(MODIFY_REPLACE, [user.email])],
+        "cn":           [(MODIFY_REPLACE, [user.first_name])],
+        "sn":           [(MODIFY_REPLACE, [user.last_name])],
+        "displayName":  [(MODIFY_REPLACE, [user.display_name])],
+        "jpegPhoto":    [(MODIFY_REPLACE, [new_picture_bytes.getvalue()])],
+    }
+
+    connection.modify(user.get_dn(), new_attributes)
+
+
 def delete_user(connection: Connection, uid: str) -> None:
     """Deletes the user with the specified uid (username) from the LDAP server.
     
@@ -739,8 +786,14 @@ def delete_user(connection: Connection, uid: str) -> None:
     if not user_exists(connection, user_dn):
         raise EntryNotFoundException(f"No such user entry: '{user_dn}'.")
 
-    # TODO Check if user is the sole member of any groups
+    # Check if user is the sole member of any groups
     # If so, delete that group here, because groups need to have at least one member
+    groups_to_delete = set()
+    for group in get_groups_of_user(connection, get_user(connection, uid)):
+        if len(group.members) == 1:
+            groups_to_delete.add(group)
+    for group in groups_to_delete:
+        delete_group(connection, group.groupname)
 
     connection.delete(user_dn)
 
@@ -960,3 +1013,42 @@ def get_groups(connection: Connection) -> set[Group]:
         all_groups.add(get_group(connection, str(entry.cn)))
 
     return all_groups
+
+def get_groups_of_user(connection: Connection, user: User) -> set[Group]:
+    """Retrieves the set of Groups of which the specified user is a member.
+
+    Parameters
+    ----------
+    connection : ldap3.Connection
+        Bound Connection object to an LDAP server.
+    user : lumi2.usermodel.User
+        The User whose Groups to retrieve.
+
+    Returns
+    -------
+    set[Groups]
+        A set containing all Groups of which the user is a member.
+        If the specified User is not present in any groups, returns an empty set.
+
+    Raises
+    ------
+    EntryNotFoundException
+        If no entry for the specified User exists.
+    TypeError
+        If user is not of type User.
+    """
+
+    _assert_is_valid_connection(connection)
+    if not user_exists(connection, user.get_dn()):
+        raise EntryNotFoundException(
+            f"Failed to get Groups of User '{user.username}': the entry " \
+            f"'{user.get_dn()}' does not exist."
+        )
+
+    all_groups = get_groups(connection)
+    result = set()
+    for group in all_groups:
+        if user in group.members:
+            result.add(group)
+
+    return result