After failed more then 10 times, I found the solution as follows:
Now you need to edit /etc/yum.repos.d/CentOS-Base.repo and add these priorities to the bottoms of each of the following repo sections:
Save your changes on this file and edit the rpmforge.repo file. You’ll only need to edit the one repository section.
Save your changes and you’re finished.
Setting this repo to a higher priority ensures that this repo is only used if the other repos don’t have what you’re looking for. Like Pure-FTPd. The above assumes you’re using 64bit Centos 6. if you’re using 32bit today stop and ask yourself why. Then, use the link and substitute the 32 bit links instead.
In this case we don’t see Pure-FTPd in the stock CentOS repos. let’s update yum and then install PureFTPd.
yum install pure-ftpd
Then follow the document: http://wiki.apache.org/couchdb/Installing_on_RHEL5