I had a problem with running a `yum update` on some package. The process would sleep indefinitely. A clue that something was wrong with the RPM database (at `/var/lib/rpm`) was that running `rpm -qa` would hang as well.

The solution is to rebuild the RPM database. In short:

    # Backups!
    tar -czvf /tmp/rpm.tgz /var/lib/rpm

    # Remove the database locks
    rm -f /var/lib/rpm/__db*

    # Rebuild!
    rpm -vv --rebuilddb

That should do it.