A
Unix copy command with special options suitable for
block-oriented devices; it was often used in heavy-handed
system maintenance, as in "Let's "
dd" the
root partition
onto a tape, then use the
boot PROM to load it back on to a
new disk".
dd had a distinctly non-Unixy keyword option syntax
reminiscent of
IBM System/360 JCL (which had an elaborate
DD "Dataset Definition" specification for I/O devices).
Though the command filled a need, the interface design was
clearly a prank.
[
Jargon File]
(2005-08-08)