[root@test mysql]# innobackupex --host=192.168.1.156   --user=root --password=123.com --defaults-file=/etc/my.cnf --database=‘test‘ /opt/backup/

InnoDB Backup Utility v1.5.1-xtrabackup; Copyright 2003, 2009 Innobase Oy
and Percona LLC and/or its affiliates 2009-2013.  All Rights Reserved.

This software is published under
the GNU GENERAL PUBLIC LICENSE Version 2, June 1991.

Get the latest version of Percona XtraBackup, documentation, and help resources:
http://www.percona.com/xb/p

170429 21:06:46  innobackupex: Connecting to MySQL server with DSN ‘dbi:mysql:;mysql_read_default_file=/etc/my.cnf;mysql_read_default_group=xtrabackup;host=192.168.1.156‘ as ‘root‘  (using password: YES).
innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 3003
    main::mysql_connect(‘abort_on_error‘, 1) called at /usr/bin/innobackupex line 1539
innobackupex: Error: Failed to connect to MySQL server: DBI connect(‘;mysql_read_default_file=/etc/my.cnf;mysql_read_default_group=xtrabackup;host=192.168.1.156‘,‘root‘,...) failed: Access denied for user ‘root‘@‘192.168.1.156‘ (using password: YES) at /usr/bin/innobackupex line 2987

　　1.授权法。例如，你想root使用123.com从任何主机连接到mysql服务器的话。 
　　 mysql>GRANT ALL PRIVILEGES ON *.* TO ‘root‘@‘%‘IDENTIFIED BY ‘123.com‘ WITH GRANT OPTION; 
　　 如果你想允许用户root从ip为192.168.1.156的主机连接到mysql服务器，并使用123.com作为密码 
　　 mysql>GRANT ALL PRIVILEGES ON *.* TO ‘root‘@‘192.168.1.156‘IDENTIFIED BY ‘123.com‘ WITH GRANT OPTION; 
　　 mysql>FLUSH RIVILEGES 
　　 使修改生效，就可以了 
　 
　　2、mysql>GRANT ALL PRIVILEGES ON *.* TO ‘root‘@‘%‘WITH GRANT OPTION 
　　//赋予任何主机访问数据的权限 
　　　mysql>FLUSH PRIVILEGES 
　　//修改生效