 Rocks was initially based on the Red Hat Linux distribution, however modern versions of Rocks were based on CentOS, with a modified Anaconda installer that simplifies mass installation onto many computers.Rocks includes many tools (such as MPI) which are not part of CentOS but are integral components that make a group of computers into a cluster.Installations can be customized with additional software packages at install-time by using special user-supplied CDs (called "Roll CDs").