TUHS

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6420 discussions

Re: [TUHS] Work I've done with a PDP-11 simulator

by jnc＠mercury.lcs.mit.edu

> From: John Cowan <cowan(a)mercury.ccil.org> > If you haven't already, see > <http://pdos.csail.mit.edu/6.828/2004/homework/hw5.html> et seqq. I had seen a later variant of that course; I wasn't aware that an earlier one used Unix; thanks for the pointer. It's a bit unfortunate (from my PoV) that in the Unix coverage they seemed to mostly focus on the low-level mechanics (e.g. how stacks are switched, etc, etc), and not on the (to me) more interesting lessons to be learned from V6 - most notably, how to get so much bang for so little buck! (I am convinced that one of the primary challenges facing computer science these days is control of complexity, but I don't want to get way off-topic, so I'll stop there.) Although I suppose things like that have to be covered at some point, and they might as well do it in V6 as in anything else! Noel

10 years, 9 months

Work I've done with a PDP-11 simulator

by jnc＠mercury.lcs.mit.edu

Hello, all: I'm working (long-term) on a project to bring back to life the V6+ Unix system (it wasn't vanilla V6 - it looks like it had some PWB stuff added) that was used on a number of machines at the Laboratory for Computer Science at MIT in the late 70s - early 80s. As part of that, I've been playing with bringing up V6 on a PDP11 simulator, and have written some stuff that would probably be useful to anyone who's interested in bringing up Unix on a PDP-11 simulator. I used the Ersatz-11 simulator from D-Bit (for no particularly good reason, except it runs under Windoze, and the "FAQ on the Unix Archive and Unix on the PDP-11" page said it was the fastest). I have been very pleased with this simulator; it is indeed fast (my simulated 11/70 runs at about 100 MIPS on a relatively elderly Athlon, which is about 30 times as fast as a real one used to :-), and it has lots of nice features (e.g. you can TELNET in to a terminal port on the simulated PDP-11). It also has this nice virtual device that allows a program running on the simulated PDP-11 i) access to files in the Windows file system, and ii) to issue commands to the emulator. I have written a V6 driver for it (should be fairly easy to adapt to V7 or later), and a suite of Unix commands to grab a file off the Windows file system (both binary and text mode), and issue various commands to the simulator. Finally, I have a number of Windows commands to do various useful things, such as read a file off a simulated Unix V6 file system (hosted in a Windows file), including ports of a number of Unix commands (e.g. ncheck, nm, etc); I don't detail them all here as I don't want this email to get too long (and boring). I'm not sure if anyone's interested in any of this; if so, I can send in more info (or whip up a Web page, whichever would be better). I also ran into a number of pitfalls on the way to getting V6 running, using RK05 disk images from the TUHS archive, and I can do a short writeup on 'How to bring up V6 under Ersatz-11' if anyone's interested. Noel

10 years, 9 months

Re: [TUHS] Work I've done with a PDP-11 simulator

by jnc＠mercury.lcs.mit.edu

> On Sat, May 03, 2014 at 06:20:55PM -0400, Gregg Levine wrote: > What he said. I believe we all are interested. OK, I have whipped up some material on how to bring V6 up under Ersatz-11. See here: http://ana-3.lcs.mit.edu/~jnc/tech/unix/V6Unix.html That page covers i) how to get the emulator, V6 Unix disks, and what you need to do start it running, and then ii) some of the initial steps to take past that to improve to working environment. Included in that are a couple of things I tripped over, and how to avoid them. The latter part assumes you want to do something more than just start it, so you can see it start up; it includes coverage of the commands that work with the emulator's "DOS device" to do things like read files off the host machine into the Unix; a serious problem on V6 Unix having to do with 21st Century dates; a 'more' command for V6 Unix (Vanilla V6 was back before the days of video terminals... :-); the ability to TELNET into the emulator; and some useful Windows commands (e.g. to read files out of the Unix into the host machine, and create blank disk pack files); and finally configuration file for the E11 emulator. There is more content/pages coming: the start of an 'advanced things you can do to improve your V6 Unix' page, which includes the new C compiler [the 'vanilla' V6 C compiler does not handle longs, unsigned, casts, and a bunch of other things]; tar; the Standard I/O library; etc is already there, but unfinished. And I have some material on things you can trip over in porting stuff back and forth (I found some doozies trying to make V6 commands run under Windoze), etc. But that will be later. For now, I'm interested in hearing: of any errors or issues with the first page; whether people find it completely incomprensible, or totally fantastic (or whereever on the axis between them it lies); what additional topics I should cover; etc, etc. Let me know! And enjoy your V6 experience! Noel

10 years, 9 months

Re: [TUHS] TUHS Digest, Vol 112, Issue 1

by jnc＠mercury.lcs.mit.edu

> From: Doug McIlroy <doug(a)cs.dartmouth.edu> > I didn't realize that MIT had PDP-11 Unixes. Yes; I don't know exactly when the first one arrived, but I'm pretty sure it was around the end of my freshman year (i.e. the summmer of '75), because I remember a friend showing me Unix sometime in my sophmore year, and they already had it as a going concern then. The first one (I think) at MIT was the 11/70 belonging to the Domain-Specific Systems Research group at LCS (DSSR). I got a copy of theirs for the Computer Systems Research group (CSR) at LCS, that would have been in the fall of '77. I don't think the AI Lab ever had one; with us all together in 545 Tech Sq I think I would have heard (although maybe the Turtle guys on the third floor had one). There were probably others on campus, but Unixes could be pretty small, and MIT is big enough that the left hand wouldn't know of the right (and 545 Tech Sq was kind of insulated from the rest of campus anyway). One I recollect on main campus later on was somewhere in the EE department - maybe Speech? They had the CHAOS protocols installed on it - that was later, say '79-'80 or so. > Other places didn't worry about it, with John Lyons' V6 book being the > biggest leak. Not to mention things like the ACM paper, which was public domain... > From: Win Treese <treese(a)acm.org> > As I understood it, MIT's main objection was that they didn't want to > get entangled in anything that would require students to sign non-disclosure agreements. That sounds likely. > At some point, MIT did have a license with Western Electric that did > not have such a requirement. I'm pretty sure it was at least V7, and > possibly 32V; not sure about V6. Well, I don't know about the license (MIT had a student who was an intern at Bell, and I think a lot of stuff slipped out the back door with him :-), but MIT definitely had V6 in 1976 or so, and V7 wasn't released until 1979. So we had it long before V7. Plus to which I have listings of the kernel; it's definitely pre-V7, but it's not vanilla V6, it has some other stuff in it (I think it's probably PWB). Noel

10 years, 9 months

Re: [TUHS] TUHS Digest, Vol 112, Issue 1

by Doug McIlroy

> V6 ... on a number of machines at the Laboratory for Computer > Science at MIT in the late 70s - early 80s Interesting. I didn't realize that MIT had PDP-11 Unixes. When university CS departments were snapping up licenses right and left, MIT demurred because AT&T licensed it as a trade secret and MIT's lawyers (probably rightly) feared there was no way they could keep Unix knowledge from contaminating research projects. Other places didn't worry about it, with John Lyons' V6 book being the biggest leak. AT&T lawyers did clamp down on general distribution of the book, but Bell Labs eagerly hired Lyons for a sabbatical visit. Did MIT's lawyers relent by V6 time, or did LCS somehow circumvent them? Doug

10 years, 9 months

OT: Andy Warhol images recovered from 1985 amiga system

by Aharon Robbins

For those of you into retrocomputing: http://studioforcreativeinquiry.org/events/warhol-discovery Arnold

10 years, 9 months

Re: [TUHS] History of chown semantics

by Brian S Walden

the short: yes you could chown your own files in 1st to 5th editions, the first pwb was a derivition of 4th ed, so its not the originator of the idea. the long: that "superuser could not even chown setuid files" awoke a long dead memory. I needed to go back to read the 1st ed man entries for chown(1) and (2) again ( see http://cm.bell-labs.com/cm/cs/who/dmr/1stEdman.html inc. below) and it is documented that yes, one indeed could give away their own files. also note 1st ed was pre-gid, files had only owner and non-owner, so no setgid to worry about. looking more 2nd and 3rd ed were the same (see ttp://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v2/v2man.pdf and http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v3/v3man.t…) however in the 3rd ed there were now gids yet no restistions on chown of setgid files. 4th and 5th ed still allowed file give away even if the setuid bit was set by stripping that bit out (unless superuser) (but did not strip the setgid bit) (see http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v4/v4man.t… and http://www.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v5/v5man.p…) The 6th ed and on is when only the superuser could change file owners. Since the first PWBs were derived from 4th and 5th editions, they just did not buy into the new chown() restrictions from v6 (and added the missed strippig of the setgid bit) 1st Ed manual enries -- 11/3/71 CHOWN (I) NAME chown -- change owner SYNOPSIS chown owner file DESCRIPTION owner becomes the new owner of the files. The owner may be either a decimal UID or a name found in /etc/uids. Only the owner of a file is allowed to change the owner. It is illegal to change the owner of a file with the set-user- ID mode. FILES /etc/uids SEE ALSO stat DIAGNOSTICS BUGS OWNER ken, dmr 11/3/71 SYS CHOWN (II) NAME chown -- change owner of file SYNOPSIS sys chown; name; owner / chown = 16. DESCRIPTION The file whose name is given by the null-terminated string pointed to by name has its owner changed to owner. Only the present owner of a file (or the super-user) may donate the file to another user. Also, one may not change the owner of a file with the set-user-ID bit on, otherwise one could create Trojan Horses able to misuse other's files. FILES SEE ALSO /etc/uids has the mapping between user names and user numbers. DIAGNOSTICS The error bit (c-bit) is set on illegal owner changes. BUGS OWNER ken, dmr > From Doug McIlroy <doug(a)cs.dartmouth.edu> > > Indeed, research Unix never allowed ordinary users to > change a uid. And even in the first edition, the superuser > was not allowed to do so on set-uid files, presumably to > prevent inadvertent laying of cuckoo eggs. The v6 note > about interaction with accounting reflected field > experience with the overly liberal stance of other Unixes. >

11 years

Re: [TUHS] History of chown semantics

by Pepe

On Tuesday, January 14, 2014 2:00 AM [GMT+1=CET], John Cowan wrote: > SZIGETI Szabolcs scripsit: > > > Well, with the same reasoning, we don't need passwords or protection > > bits on files, since I can always take a piece of steel pipe and > > beat the owner, until he gives out the data, so why bother? > > More like beating my argument with a pipe than the owner. > > > Blocking chown for general users is one level of several controls. > > Its specific purpose was to make per-user quotas practical, but since > per-user quotas are as dead as the dodo, it no longer serves any known > purpose. I don't think quotas are dead. It seems nowadays the "preferred" storage backend for email on Unix/Linux mail servers is Maildir, and Maildir uses the filesystem as its own backend, together with the filesystem's quota facility to give or take storage space to/from mailboxes -- yes, provided the users are real system users and not "virtual users", but still. What is "dead as the dodo" is multi-user shell access. But that does not mean multi-user shell access should be removed from modern systems, no matter how dead it may be. -Pepe.

11 years

History of chown semantics

by Tim Bradshaw

Sorry if this is off-topic but I bet someone here will know. I recently had a significant surprise when I discovered that on HP-UX ordinary users can still give away files. Various of us who remember fairly old Unixes then sat around trying to remember which systems had this and where it came from: getting it almost entirely wrong, it turns out. What we remembered was that it came from BSD, but this seems to be entirely wrong. It looks like it originated with System III / V, and perhaps was imported from there into some SunOS (possibly it was in all versions before Solaris?) which is why we remember it as being in BSD. It must have been in some 80s system or we would not remember it. POSIX still allows it but clearly reluctantly. So the questions are: (a) did it originate in System III or does it go back further than that, and (b) was it in the BSD-derived SunOSes or are we just making that up? And I guess: who thought this was a good idea? Thanks --tim

11 years

Re: [TUHS] History of chown semantics

by Brian S Walden

Yea, but that was all much later. It wasn't a problem with PWB as it's file system structure, in practice, was /u[0-9]/{projectname}/{username} so when a mount point ran low on space it wasn't the individual user that got hassled, but the projects under the mount. Makes disc usage accounting easy too, if it's under the project, the project pays for it. You can see that structure and how PWB was actually used by a project at http://9grid.org.uk/pwb/users-view.pdf > From: Ed Carp <erc(a)pobox.com> > > But it was fun to give away large files to someone else to avoid getting > hassled by a sysadmin when you were close to filling up your disk quota. :)

11 years

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