MariaDB ERROR 1524 Plugin unix_socket is not loaded

After upgrading MariaDB on Ubuntu server, i got following error

root@server:~# mysql
ERROR 1524 (HY000): Plugin 'unix_socket' is not loaded
root@server:~#

Users created worked fine. Only root user had this error.

To fix, you need to enable auth_socket.so plugin.

Edit file

vi /etc/mysql/mariadb.conf.d/50-server.cnf

Find

[mysqld]

Add below

plugin-load-add = auth_socket.so

Resatrt MariaDB

systemctl restart mysqld