在CentOS Release 6.6安装percona-xtrabackup-2.3.4时，遇到下面错误信息
rpm -ivh percona-xtrabackup-2.3.4-1.el6.x86_64.rpm
在 https://bugs.launchpad.net/percona-xtrabackup/+bug/1526636上看到，这个是一个bug来着，在 percona-xtrabackup (2.3.2-1)已经出现了。具体可以参考Bug #1526636 - by mentioning hard requirement on libev package in rpm distros
其实是因为percona-xtrabackup依赖libev.so.4()(64bit)的包，而这个包只能从EPEL源(Extra Packages for Enterprise Linux，企业版Linux的额外软件包 是Fedora小组维护的一个软件仓库项目，为RHEL/CentOS提供他们默认不提供的软件包)安装 ,所以只要安装了这个包即可解决问题.
When installing the latest release of percona-xtrabackup (2.3.2-1) from the percona repo, it encounters a missing dependency for libev.so.
Error: Package: percona-xtrabackup-2.3.2-1.el6.x86_64 (percona)
Requires: libev.so.4()(64bit)
This can be resolved by installing an external repo such as EPEL, but probably should be included in the percona repo. Alternatively switching to AnyEvent (if EV is not a hard requirement) would allow for EV or the internal loop if EV is not installed on a system.
Have not tested this issue with other releases of CentOS.
从http://rpmfind.net/linux/rpm2html/search.php上下载libev-4.15-1.el6.rf.x86_64.rpm安装包，然后安装即可，如下所示
[root@MySQL-DB tmp]# rpm -ivh libev-4.15-1.el6.rf.x86_64.rpm
warning: libev-4.15-1.el6.rf.x86_64.rpm: Header V3 DSA/SHA1 Signature, key ID 6b8d79e6: NOKEY
Preparing... ########################################### [100%]
1:libev ########################################### [100%]
[root@MySQL-DB tmp]# rpm -ivh percona-xtrabackup-2.3.4-1.el6.x86_64.rpm
warning: percona-xtrabackup-2.3.4-1.el6.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID cd2efd2a: NOKEY
Preparing... ########################################### [100%]
1:percona-xtrabackup ########################################### [100%]
[root@GETAZLNX002 tmp]#
[root@MySQL-DB tmp]# rpm -ivh percona-xtrabackup-debuginfo-2.3.4-1.el6.x86_64.rpm
warning: percona-xtrabackup-debuginfo-2.3.4-1.el6.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID cd2efd2a: NOKEY
Preparing... ########################################### [100%]
1:percona-xtrabackup-debu########################################### [100%]
[root@MySQL-DB tmp]# rpm -ivh percona-xtrabackup-test-2.3.4-1.el6.x86_64.rpm
warning: percona-xtrabackup-test-2.3.4-1.el6.x86_64.rpm: Header V4 DSA/SHA1 Signature, key ID cd2efd2a: NOKEY
Preparing... ########################################### [100%]
1:percona-xtrabackup-test########################################### [100%]
[root@MySQL-DB tmp]#
参考资料：
https://bugs.launchpad.net/percona-xtrabackup/+bug/1526636
https://github.com/percona/percona-xtrabackup/pull/181
