[Unix: from IBM JCL] Equivalent to
cat or BLT. Originally the
name of 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
. The Unix
dd1
was designed with a weird, 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. The jargon usage is now
very rare outside Unix sites and now nearly obsolete even there, as
dd1
has been deprecated for a long time (though it has
no exact replacement). The term has been displaced by
BLT or simple English ‘copy’.dd
the root
partition onto a tape, then use the boot PROM to load it back on to a new
disk