Farkas' solution is exactly right. I have been banging my head against this problem for a while now and it wasn't until I finally paced myself and read carefully through the entire thread that I found this solution. Here is the procedure spelled out a bit more precisely. Get the CentOS 5.2 rpms of popt, rpm, rpm-libs, rpm-python and rpm-build. Obviously you can use most any mirror and if you are using i386 you should replace x86_64 with i386. I prefer to use RIT since its my Alma Mater and they seem to have good bandwidth and keep older versions. # wget http://mirrors.rit.edu/centos/5.2/os/x86_64/CentOS/popt-1.10.2-48.el5.x8 6_64.rpm # wget http://mirrors.rit.edu/centos/5.2/os/x86_64/CentOS/rpm-4.4.2-48.el5.x86_ 64.rpm # wget http://mirrors.rit.edu/centos/5.2/os/x86_64/CentOS/rpm-build-4.4.2-48.el 5.x86_64.rpm # wget http://mirrors.rit.edu/centos/5.2/os/x86_64/CentOS/rpm-libs-4.4.2-48.el5 .i386.rpm # wget http://mirrors.rit.edu/centos/5.2/os/x86_64/CentOS/rpm-python-4.4.2-48.e l5.x86_64.rpm It took some testing but because we are rolling back several packages RPM handled the dependencies a little weird but here's the rpm command that does all the magic. # rpm -Uvh --oldpackage --nodeps popt-1.10.2-48.el5.x86_64.rpm rpm-4.4.2-48.el5.x86_64.rpm rpm-libs-4.4.2-48.el5.i386.rpm rpm-python-4.4.2-48.el5.x86_64.rpm --nodeps is required because rpm complains about needing to fill some dependencies for 4.4.2-48 but we are in fact trying to install those very dependencies so we have to tell rpm not to bother. If you are concerned throw in a --test switch to make sure everything goes well. I never like using rpm to roll back rpm, just seems dangerous, like crossing the streams. After rolling back to the CentOS 5.2 versions of popt, rpm, rpm-libs and rpm-python I am able to successfully init the epel-5-i386 mock root. I tested several times and made sure to clear the build root and yum caches in my tests. Farkas' suggested this might be a bug in rpm or popt which seems to hold true. Clearly between point releases something changed that caused rpm to behave slightly differently when it comes to ordering transactions. I am comfortable now using the slightly outdated RPMs but I wonder what will happen in CentOS 5.4/5.5 and so on. Regards, -Alan KEYWORDS: mock 0.9.14, CentOS 5.3, coreutils 5.97, pam 0.99.6.2