From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=MAILING_LIST_MULTI, NICE_REPLY_A,RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 29712 invoked from network); 29 Jul 2020 14:30:47 -0000 Received: from minnie.tuhs.org (45.79.103.53) by inbox.vuxu.org with ESMTPUTF8; 29 Jul 2020 14:30:47 -0000 Received: by minnie.tuhs.org (Postfix, from userid 112) id C8F2E9CACA; Thu, 30 Jul 2020 00:30:38 +1000 (AEST) Received: from minnie.tuhs.org (localhost [127.0.0.1]) by minnie.tuhs.org (Postfix) with ESMTP id 150E19CAA8; Thu, 30 Jul 2020 00:29:52 +1000 (AEST) Received: by minnie.tuhs.org (Postfix, from userid 112) id DD85F9CABA; Thu, 30 Jul 2020 00:29:37 +1000 (AEST) Received: from GW.SoftJAR.SE (gw.softjar.se [213.115.73.154]) by minnie.tuhs.org (Postfix) with ESMTP id 4CE6B9CAA9 for ; Thu, 30 Jul 2020 00:29:34 +1000 (AEST) Received: from Trollet.BQTnet.SE (80-219-208-146.dclient.hispeed.ch [80.219.208.146]) by GW.SoftJAR.SE (Postfix) with ESMTPSA id CA0FF38FCEF; Wed, 29 Jul 2020 16:29:31 +0200 (CEST) (envelope-from bqt@softjar.se) To: John Cowan References: <6a0063f8-128d-751d-114f-a0f811d02098@gmail.com> <2cb3ad2a-f8c5-a003-661c-e257f7cbe38c@softjar.se> From: Johnny Billquist Organization: SoftJAR AB Message-ID: Date: Wed, 29 Jul 2020 16:30:11 +0200 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [TUHS] [simh] 2bsd tarball X-BeenThere: tuhs@minnie.tuhs.org X-Mailman-Version: 2.1.26 Precedence: list List-Id: The Unix Heritage Society mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: TUHS main list , simh@groups.io Errors-To: tuhs-bounces@minnie.tuhs.org Sender: "TUHS" Yes. That is a much better way to look at it. Johnny On 2020-07-29 15:52, John Cowan wrote: > When I talk about DECtape in my capacity as the local old fart, i > describe it as "a disk with one track and about 1500 small sectors that > spins ve-ry ve-ry slow-ly.. > > On Wed, Jul 29, 2020 at 5:58 AM Johnny Billquist > wrote: > > Just a small comment. Whoever it was that thought DECtape was a tape > was > making a serious mistake. DECtapes are very different from magtapes. > >    Johnny > > On 2020-07-29 02:21, Clement T Cole wrote: > > > > Cross posting to simh - since much of this has been discussed in the > > last few days there also.... > > > > in for penny, in for pound ... here is the history ...  man ... I > lived > > this and I'll need a strong drink later tonight after I write it > all up. > > > > > > On Tue, Jul 28, 2020 at 7:04 PM Will Senn > > >> wrote: > > > >     I recall having to do something with cont.a files, which are not > >     present on these images. So, my questions is, does anyone > know of or > >     have an actual 2bsd tape/tape image? > > > > cont.a is a tp-v6 and earlier ism. > > > > DECtape had a directory at the front of the tape (think > > superblock/ilist), but could do cool things and be treated more > like a disk. > > When tp was created for a very early version of Unix (I'm not sure > > which, could be V2), Ken/Dennis et al had DECtape units and so the > > original scheme followed the media.   This also meant that the > program > > could write files and go back and update the directory, which is > a no-no > > with many tape systems.  Then research got a 9-track unit.   So > tp was > > changed to calculate how much space was going to be needed, write > the > > directory, then the datablocks.  All good ... except... > > > > 9-track could write more files than the directory could take. >  So for > > many years, people would use the ar(1) program to take a number > of files > > in a directory, create a file called cont.a and then delete the > files. > > Then the tree would be written with tp, when you read it, you > reversed > > the ar(1) process.  If you look at the USENIX/Harvard tape on the > TUHS > > you'll see this scheme in use. > > > > BTW: tp was written in assembler and all the data structures were > using > > PDP-11 binary formats.  Eventually, Harvard wrote stp (super-tp) > in C > > (which is on the USENIX tape Warren has in the archives) that worked > > like the original assembler tp but also put a redundant directory > at the > > end of the tape.  Another issue with tp was if the you had a bad > block > > in the first few blocks you could not decode the rest of the tape. > > [There were some other issues with the UNIX tree structure as > disks got > > bigger but I'm going to ignore all that - other than to say, tp had > > lived it life]. > > > > Enter Mashey and the PWB 1.0 folks (which is based on V6). > Someone in > > USG created cpio (and volcpy) as part of the PWB 1.0.   Like tp > it was a > > PDP-11 binary format, but unlike tp, the tape directory is threaded. > > /i.e./ block one describes the first file only and includes the > size of > > the following file, then file itself, then a new directory block > for the > > next file and again that file (rinse and repeat).  So it improved > on tp > > in the directory threading, but was still binary and for a > reasons I'll > > leave out had a different user interface. > > > > As part of V7, Ken wrote a new program, tar [you can ask him > why].  But > > like cpio he used a threaded tape directory, but unlike cpio it was > > always ASCII and not PDP-11 specific.  Furthermore, the user > interface > > was made to parrot tp.  So, certainly, it had the advantage that > > changing tp scripts to use tar was pretty easy i.e. s/tp/tar/ >  not so > > for coil.  And it was muscle memory compliant. > > > > For PWB 2.0, cpio was updated to allow a -c option to write the > header > > in ascii and -s to byte swap the binary.   But the damage had > been done ... > > > > Thus began 'tar wars' which was a battle that raged officially > over tape > > archive formats, but really was an argument about user interfaces. > > Since tar was part of Research and the Universities and commercial > > people used it, only USG and the folks inside the Bell System > were using > > cpio, as officially none of us had it since PWB was not released > to us > > (although thanks to many AT&T employees doing an OYOC year, many > schools > > like UCB, MIT and CMU all had the sources to cpio anyway -- for > instance > > you'll see it hidden away on Kirk's CD). > > > > I personally had used both, preferred tar for easy of use and ASCII > > directories.  But, note I had written car at Masscomp, but never > tpio. > > This was our trick to use the file scripting list that cpio could > do, > > but create tar format tapes - which was handy.  I never wrote > tpio which > > would have been cpio format using tp/tar user interface as I did not > > need it. > > > > Roll forward to the /usr/group UNIX standard that Heinz chaired.  We > > ended up not being able to agree on a distribution format, but > the ISVs > > were PO because now they could create UNIX programs that might > actually > > work across systems, but they had not standard way to distribution. > > Roll forward again to IEEE.  Heinz's committee was officially > disbanded > > (story discussed elsewhere) and we were created as IEEE P1003 > with Jim > > Issack as Chair. This time the ISV's said we had to have a > distribution > > format.  Since *.1 was only an API we were allowed to avoid the user > > interface issue but only examine the on tape format. > > > > It turns out while it seems to have been unintended, Ken's > original V7 > > implementation has an interesting coding feature/bug which turns > out to > > be what clinched the deal.   When Ken creates the directory block > for > > each file, he did bcopy of 0's to the buffer before he wrote that > data > > that fills it in.  Then when he calculated the checksum for the > > directory header block, he summed the entire block (which because > of the > > bcopy was zeros).  This means if you write beyond the end of Ken's > > original header and include that extra data in the chksum, the > original > > program will ignore the new information but accept the directory > block > > as valid.  i.e. he had built an extension mechanism into the tar > on-tape > > format. > > > > cpio's ASCII on tape format was not able to do that as the > checksum used > > a sizeof(header struct) in the checksum routine. > > > > USTAR was born ... Ken had written things like the UID/GID as ASCII > > representations of the integer value in the original header.  USTAR > > added the ASCII representation of the username and the group name > since > > that was more often portable between systems than the numbers. >  There > > were other additions like more room for the pathname new file types > > /etc/.  But the key is that a USTAR tape can be read by the > original V7 > > (and follow on) tape formats, although may not recognize all the > > filetype or use all of the new information. > > > > A few years later during *.2 discussions, we finally got into the > user > > interface stuff and pax(1) was born.  Knowing my hack with car, > Keith > > Bostic, Jim McGuiness and I wrote up a description of a program that > > could with both users interfaces scheme.  USENIX provided funding > for a > > student to implement it and put the sources out on > comp.unix.sources at > > some point.  That proposal was originally accepted at the first tape > > user interface program in *.2 [a few years later after I stopped > being > > part of the committee, the USG folks did get an alternate CPIO > format > > accepted and cpio as an allowed program.   USENIX paid to have the > > program updated to operate like cpio if it was called that, pure > V7 tar > > if called that and if pax, user USTAR]. > > > > 'nuf said ... I hope. > > > > Clem > > > > _._,_._,_ > > > ------------------------------------------------------------------------ > > Groups.io Links: > > > > You receive all messages sent to this group. > > > > View/Reply Online (#62) | > Reply To > > Group > > ?subject=Re:%20Re%3A%20%5Bsimh%5D%20%5BTUHS%5D%202bsd%20tarball> > > > | Reply To Sender > > ?subject=Private:%20Re:%20Re%3A%20%5Bsimh%5D%20%5BTUHS%5D%202bsd%20tarball> > > > | Mute This Topic | New > Topic > > > > > > Your Subscription | > Contact > > Group Owner > | Unsubscribe > > > [bqt@softjar.se ] > > > > _._,_._,_ > > -- > Johnny Billquist                  || "I'm on a bus >                                    ||  on a psychedelic trip > email: bqt@softjar.se              || > Reading murder books > pdp is alive!                     ||  tryin' to stay hip" - B. Idol > -- Johnny Billquist || "I'm on a bus || on a psychedelic trip email: bqt@softjar.se || Reading murder books pdp is alive! || tryin' to stay hip" - B. Idol