Extract/build from SRPMS
for example, if we want to work on the quota utilities:
wget http://vault.centos.org/6.5/os/Source/SPackages/quota-3.17-20.el6.src.rpm rpm -ivv quota-3.17.20.el6.src.rpm cd /root/rpmbuild/SPECS rpmbuild -bp quota.spec
quota has two dependencies: nss-devel and tcp_wrappers-devel
yum install nss-devel yum --enablerepo=base,extras install tcp_wrappers-devel rpmbuild -bp quota.spec # try it again -- works
Then move to source build directory:
Do what you need to the source...