ERROR 1045: Access denied for user root@localhost


I am new to ERPNext. I am getting this error when I am doing anything at all. I am not able to create a new site on bench or do anything else at all. Can you please let me know what the problem could be?

umag@epochuma:/$ mysql -u root
ERROR 1045 (28000): Access denied for user ‘root’@‘localhost’ (using password: NO)