RE: Installing rpm-build using yum

 We have only one section owning core in fedore-core.repo.

cat fedora-core.repo
[core]
name=Fedora Core $releasever - $basearch
#baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/$releasever/$basearch/os/
#baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/5/x86_64/os
baseurl=http://download.fedora.redhat.com/pub/fedora/linux/core/5/i386/os
mirrorlist=http://fedora.redhat.com/download/mirrors/fedora-core-$releasever
mirrorlist=http://download.fedora.redhat.com/pub/fedora/linux/core/5/i386/os
#mirrorlist=http://fedora.redhat.com/download/mirrors/updates-released-fc5
#mirrorlist=http://download.fedora.redhat.com/pub/fedora/linux/core/5/x86_64/os
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora file:///etc/pki/rpm-gpg/RPM-GPG-KEY