This release was maintained with up2date
and Yum was yet to come. To enable
installation with yumbootstrap, you need to prepare Yum metadata. After this,
installation should go just fine.
CentOS just works on this matter, though. CentOS 4 (http://vault.centos.org/) already provides Yum metadata, along with yum package.
yumbootstrap can't use RHN as a repository. A workaround is to clone
repository from RHN with reposync
(yum-utils).
Yum changed some repository internals, so installing RHEL6 doesn't work under RHEL5 (older Yum can't find some files).
Installing Fedora under Debian 6 (Squeeze) fails due to a bug (probably in python-rpm). Installation under Debian 7 (Wheezy) works correctly.
Fedora's repository URL often redirects to poorly maintained mirrors (missing files, incorrect permissions etc.), causing installation to fail. A workaround is to figure a good mirror and replace URL with that.