yum install libxml2.so.2 zlib 出错

yum 安装 libxml2.so.2 的时候报如下错误：

错误： Multilib version problems found. This often means that the root
      cause is something else and multilib version checking is just
      pointing out that there is a problem. Eg.:
      
        1. You have an upgrade for libxml2 which is missing some
           dependency that another package requires. Yum is trying to
           solve this by installing an older version of libxml2 of the
           different architecture. If you exclude the bad architecture
           yum will tell you what the root cause is (which package
           requires what). You can try redoing the upgrade with
           --exclude libxml2.otherarch ... this should give you an error
           message showing the root cause of the problem.
      
        2. You have multiple architectures of libxml2 installed, but
           yum can only see an upgrade for one of those arcitectures.
           If you don't want/need both architectures anymore then you
           can remove the one with the missing update and everything
           will work.
      
        3. You have duplicate versions of libxml2 installed already.
           You can use "yum check" to get yum show these errors.
      
      ...you can also use --setopt=protected_multilib=false to remove
      this checking, however this is almost never the correct thing to
      do as something else is very likely to go wrong (often causing
      much more problems).
      
      Protected multilib versions: libxml2-2.7.6-17.el6_6.1.i686 != libxml2-2.7.6-14.el6_5.2.x86_64

-------------所以，

重新执行

yum install libxml2.so.2 --setopt=protected_multilib=false

成功执行结果：

执行事务
  正在安装   : zlib-1.2.3-29.el6.i686                                                                                    1/2 
  正在安装   : libxml2-2.7.6-17.el6_6.1.i686                                                                             2/2 
  Verifying  : libxml2-2.7.6-17.el6_6.1.i686                                                                             1/2 
  Verifying  : zlib-1.2.3-29.el6.i686                                                                                    2/2 


已安装:
  libxml2.i686 0:2.7.6-17.el6_6.1                                                                                            


作为依赖被安装:
  zlib.i686 0:1.2.3-29.el6                                                                                                   


完毕！