在CenOS6、RHEL6或者ORACLE LINUX 6上安装oracle 11g R2的时候提示:pdksh包没有安装，
按照提示从网上下了个pdksh-5.2.14-36.el5.i386.rpm包，然后尝试安装：
# rpm -ivh pdksh-5.2.14-36.el5.i386.rpm
warning: pdksh-5.2.14-36.el5.i386.rpm: Header V3 DSA/SHA1 Signature, key ID e8562897: NOKEY
error: Failed dependencies:
pdksh conflicts with ksh-20100621-2.el6.i686
这个问题解决非常简单：
# rpm -e ksh-20100621-2.el6.i686
# rpm -ivh pdksh-5.2.14-36.el5.i386.rpm