On CentOS, there are three root accounts for MySQL:

root@localhost - pass set by the first command

root@server1.example.com - pass set by the second command

root@127.0.0.1 - the password for this should be set like

# mysqladmin -h 127.0.0.1 -u root password xxxxxx

Check your accounts:

# mysql -p -u root
mysql> select host,user,password from mysql.user;