It's often difficult to get the BuildRequires in a spec file exactly right, because it's easy to overlook packages that are coincidentally installed on the machine. <code>mock</code> is a tool that uses the chroot system call to create a "cleanroom" environment for the build, so that any missing BuildRequires cause the build to fail. {{Admon/caution|The ''Mock'mock''' Group|To use mock, you must first add yourself is used to test that the '''mock''' groupBuildRequires for a package are complete and accurate, by creating a bare-bones [http: <code>usermod -G mock ''yourUserName''</code>}} To build with mock:  mock -r ''fedora-13-x86_64'' --rebuild ''foo*/en.srcwikipedia.rpm'' The value ''fedora-13-x86_64'' may be changed to any of the config files found in <code>org/etcwiki/mock</code> in order to test building based on Chroot chroot] environment containing only the libraries and available packages for a specific architecture and Fedora release. If errors are reported[[:fedora: Packaging/Guidelines# Review the log files (see the mock output to determine the directory containing the log files) to see what dependencies are missing.# Add these dependencies to the <code>Exceptions_2|basic build packages]] plus any packages indicated by BuildRequires</code> lines in your the spec file.# Rebuild your SRPM and repeat the mock test.