Backup adds instant version control to any file on a Unix system. It is a lightweight interface to the Subversion svn_fs library. It uses the powerful version control software as a backend to a simple and minimalistic user interface.
anything kept in reserve to serve as a substitute in case of failure or unavailability of the normal or primary object; -- used for devices, plans, people, etc. Also used attributively; as, there was no backup for the electrical supply; a backup motor; a backup generator.
A copy of a program or data from a computer onto a data-storage medium, usually one that may be removed to safe storage at a distance from the computer; it is used to preserve data for use in the contingency that the original data on the computer may be lost or become unusable. A backup that is removed from the building housing the computer system (to provide protection against loss of data in a disastrous event such as a fire) is called off-site backup. Also used attributively; as, backup copy.