先看问题：
[root@localhost ~]# innobackupex --user=root --password=131417 /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
150712 22:29:59 innobackupex: Executing a version check against the server...
150712 22:29:59 innobackupex: Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_group=xtrabackup' as 'root' (using password: YES).
innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 3011.
main::mysql_connect('abort_on_error', 1) called at /usr/bin/innobackupex line 1551
innobackupex: Error: Failed to connect to MySQL server: DBI connect(';mysql_read_default_group=xtrabackup','root',...) failed: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) at /usr/bin/innobackupex line 2995.
150712 22:29:59 innobackupex: Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_group=xtrabackup' as 'root' (using password: YES).
innobackupex: got a fatal error with the following stacktrace: at /usr/bin/innobackupex line 3011.
main::mysql_connect('abort_on_error', 1) called at /usr/bin/innobackupex line 1570
innobackupex: Error: Failed to connect to MySQL server: DBI connect(';mysql_read_default_group=xtrabackup','root',...) failed: Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2) at /usr/bin/innobackupex line 2995.
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由上面可知道，innobackupex是通过socket的方式链接上去的。想办法使它不走socket就可以了。
innobackupex --user=root --password=131417 --host=127.0.0.1 /backup