http://rpm.pbone.net/
rpm -q ksh-*
rpm -e ksh-*
rpm -ivh ./pdksh*
或者参考 Requirements for Installing Oracle 11gR2 RDBMS on RHEL6 or OL6 64-bit (x86-64) (文档 ID 1441282.1)
ksh-*.el6 (x86_64) <== any version of ksh is acceptable
只要手动确认 ksh*.rpm 安装了，就可以忽略这个报错
参考:
http://vault.centos.org/
http://mirror.centos.org/centos/
http://mirror.centos.org/centos/6/os/x86_64/
ftp://ftp.muug.mb.ca/mirror/centos