mysql -u root -p
Enter password:
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Your MariaDB connection id is 47
Server version: 10.0.28-MariaDB-0ubuntu0.16.04.1 Ubuntu 16.04

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MariaDB [(none)]> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [mysql]> UPDATE mysql.user SET Grant_priv='Y', Super_priv='Y' WHERE User='root';
ERROR 1142 (42000): UPDATE command denied to user 'root'@'localhost' for table 'user'