Some of you may already be aware that doing a mock build on a FC5 machine doesn't pull in all of the packages you need to properly setup your build env. yum removed support for groupreq tags in the group definitions for version 2.6+ which prevents "yum groupinstall build" from pulling in its required groups. To fix mock builds on a machine with yum 2.6+ find the line "config_opts['buildgroup'] = 'build'" in each of your /etc/mock/*.cfg files and change it to "config_opts['buildgroup'] = 'build build-minimal build-base'". Those are all of the groups (that I know about) currently required by the group build. Everything should be happy again! There is a conversation going on in the yum-devel list about how to handle groupreq going forward. As is common in open source projects people are using features in ways that the developers didn't expect. I trust that Seth and crew will find us a good solution. Russell