Some thoughts on enhancing cpio(1)

[Kenneth Almquist]

> Does anyone *know* why USG decided to drop dump/restor and, for
> file-transfer functions, tar in favor of cpio?  This decision
> was made fairly early.  PWB 1.0 had dump/restor, I don't know
> about 2.0.  They were gone in 3.0, which was released external
> to the (then) Bell System as "System III".

I don't know, but I can guess.  They probably dropped dump/restore
because no one wanted them.  Volcopy was faster.  I expect that
dump and restore would have been retained if anybody had had a use
for them.

They didn't drop tar in favor of cpio; they dropped tp.  There were
a number of deficiencies with tp, including:
1)  It could read archives from a disk file rather than tape, but
    it could not write them.
2)  It could handle only a limited number of files specified by name
    because the names had to be passed as arguments (exec used to
    limit argument lists to 512 bytes).
3)  It didn't understand about multiple links to a file.
So USG released cpio and announced that they would drop tp eventually.
I doubt that tar existed at this point.  (If it did, USG might have
reasonably rejected it on the grounds that it solved the first problem
with tp, but not the latter two.)  Some time later USG picked up tar,
and a while after that they dropped tp, as promised.  Tar was not
dropped; it is still in System V today.  It was not widely used because
there was no good reason for users not to continue to use cpio.
				Kenneth Almquist
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