This command really helps when you don't know if a program is a part of some RPM package or when you know only what program or file you are needing but not the package. Here's RPM the command:
rpm -qf /usr/bin/smbmount
In this case it will returns the package name that contains the smbmount file:
# rpm -qf /usr/bin/smbmount samba-client-3.0.2-7.FC1
If the file is not owned by any package RPM will returns an error message.