after reset root password I still get "Access denied for user 'root'@'localhost'"

I reset the root password of the mariadb server but when I then try to login, I still get Access denied for user 'root'@'localhost'

To change the root password I did the following: (my setting: 10.0.31-MariaDB-0ubuntu0.16.04.2)

sudo service mysql stop
sudo mysqld_safe --skip-grant-tables &
mysql -u root
MariaDB [(none)]> use mysql;
MariaDB [mysql]> update user set password=PASSWORD("hello") where User='root';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
MariaDB [mysql]> flush privileges;
MariaDB [mysql]> exit
sudo service mysql stop
sudo service mysql start

mysql -u root -p
Enter password: <<== here I entered the 'hello' password but still receive:
ERROR 1698 (28000): Access denied for user 'root'@'localhost'

So, what am I doing wrong ??