Running repoclosure:

1. Create a yum.conf file which contains repository definition sections
for every repository you want to include in the check. Choose
non-ambiguous repository identifiers (to put into the section headers in
brackets, e.g. fedora-updates, because you need pass those repo ids to
repoclosure later on).

2. If the yum.conf file uses variables, such as $releasever or $basearch,
substitute these values with the "substrepo" helper script and redirect
the output to another file to continue with. Only that way you can point
repoclosure to the repositories for a specific distribution release and
target architecture. This avoids that the Yum backend fills in defaults
for your host OS.

3. Pass all repository ids to repoclosure as -r arguments.
E.g: -r fedora -r fedora-updates

4. Append the right target architecture as -a argument. Note that
for Fedora's i386 repositories, the right arch is i686 because
some packages are for i586 or higher only.

5. Don't forget option -n as you only want to consider newest package
releases.

6. The final command-line will look similar to:

  rc-modified -n -q -d ~/mdcache -c ~/yum.temp.conf \
    -a i686 \
    -r fedora-9-i386 \
    -r fedora-updates-9-i386 \
    -r fedora-updates-testing-9-i386 \
  > brokendeps-fedora-9-i386.txt