Scratch monkey
Scratch monkey is a term used in hacker jargon, as in "Before testing or reconfiguring, always mount a scratch monkey", a proverb used to advise caution when dealing with irreplaceable data or devices. It is used to refer to any temporary configuration changes to a computer during any risky operation, which include a replacement for some precious resource or data that might otherwise be destroyed.
The meaning is based upon the use in the 1970s of a scratch tape or other storage device, which was available for temporary use, to temporarily store a copy of valuable data or provide extra storage space in case a program required that space. If a problem occurred, the valuable data could be recovered from its sole remaining copy.
The phrase "always mount a scratch monkey" originated from two tales by technicians about maintenance that was performed on computer equipment. The technicians were unaware that the computer was connected to five laboratory monkeys, and the routine maintenance procedures caused the death of three of the monkeys.