TUHS January 2023

tuhs@tuhs.org

84 participants
46 discussions

by Ron Natalie

A lot of this dates back from the old “tty” days (or at least crt terminals that were still alphanumeric). Even the concept of putting a job in the background with & is really a feature of trying to multiplex multiple tasks on the same dumb terminal. This is indeed less important with windowing things like the DMDs or modern windowing workstatiosn when you can just get another window. The Berkeley job control was an interesting hack. For us at BRL the problem was I absolutely detested the C shell syntax. The Korn shell hadn’t escaped from AT&T yet, so, I spent time figuring out how that really worked in the C shell (not really well documented), mostly by inspection, and then reimplemented it in the Bourne Shell (we were using the System V source code version for that). I still couldn’t get traction at BRL for using the Bourne shell because by that time, tcsh had come out with command line editing. So back to the shell sources I went. By this time, 5R2 had come out so I grabbed the shell source form that. I was very delighted to find that the macros that made C look sorta like Algol had been unwound and the thing was back to straight C. I reworked emacs-ish command line editing into the shell. Subsequently, I had a nice conversation with David Korn at USENIX, being probably at that point the two most familiar with Bourne shell job control internals. I also sat down with the guys writing either bash or the pdksh (can’t remember which) and explained all how this work. As a result my name ended up in the Linux manpages which was pretty much all I found for a while when I googled myself. Years later, I had left the BRL, spent three years as a Rutgers administrator and was working for a small startup in Virginia. There was a MIPS workstation there. I was slogging along using ed (my employees always were amazed that if there was no emacs on the system, I just used ed, having never learned vi). Not thinking about it, I attempted to retrieve a backgrounded job by typing “fg.” To my surprise the shell printed “Job control not enabled.” Hmm, I say. That sounds like my error message. “set -J” I type. “Job control enabled.” Hey! This is my shell. Turns out Doug Gwyn put my mods into his “System V on BSD” distribution tape and it had made its way into the Mach code base and so every Mach-derived system ended up with it. Certainly, I found it convenient. There have been other schemes other than job control to multiplex terminals. IBM in the AIX that ran on the 370/PS2/i860 had a device called the High Function Terminal that allowed you to swap screens on the console. When we implemented the i860 (which was an add in card for the micro channel), we called our console the Low Function Terminal. Then after spending some time on MIT’s ITS and TOPS20, I got intrigued by the fact on those systems you could have a “shell” that persisted across logins and could be detached and reattached on another device at another time. I set about making such an implementation. Not particularly efficient, it essentially grabbed one of the BSD ptys and spawned the shell there and then a small alternative login shell forwarded the real tty to that. You could then detach it leaving the shell running on the PTY and reattach it elsewhere. Much like ITS, on. login it reminded you that you had a detached shell running and offered to reattach it rather than spawning a new one (complete with the ITS-ish: space for yes, rubout for no). It never really caught on. Oh well, pardon my ramblings. -Ron

2 years, 2 months

Thread Drift

by Warren Toomey

All, w.r.t. FD 2, if your e-mail doesn't mention file descriptors, can you please change the subject line? And this, in general, for all TUHS discussions :-) Thanks! Warren

2 years, 3 months

Sun+Java article by Bradford Morgan White

by Rich Salz

Some folks here might be interested in this. I haven't read this (not gonna subscribe), I know nothing about the author (Bradford Morgan White), but I saw Steve Sinofsky tweet good things about it. The Network is the Computer The story of Sun Microsystems and the Java programming language https://www.abortretry.fail/p/the-network-is-the-computer

2 years, 3 months

Re: Collecting notes for future “historians” was: Earliest UNIX Workstations?

by Douglas McIlroy

> * What do I really mean by workstation? Ex.gr. If an installation had a > PDP-11 with a single terminal and operator, is it not a workstation? Is it > the integration of display into the system that differentiates? Certainly integration is critical. The display should be integral to the terminal, not simply an available device. Without that stipulation Ken's original single-user PDP-7 system would count (unless, perhaps, the system had not yet been christened "Unix"). Doug

2 years, 3 months

File descriptor fun and games (setuid)

by Ron Natalie

Another of Ron’s historical diversions that came to mind. Most of you probably know of various exploits that can happen now with setuid programs, but this was pretty loose back in the early days. I was a budding system programmer back in 1979 at Johns Hopkins. Back then hacking the UNIX system was generally considered as sport by the students. The few of us who were on the admin side spent a lot of time figuring out how it had happened and running around fixing it. The first one found was the fact that the “su” program decided that if it couldn’t open /etc/passwd for some reason, things must be really bad and the invoker should be given a root shell anyhow. The common exploit would be to open all the available file descriptors (16 I think back then) and thus there wasn’t one available. That was fixed before my time at JHU (but I used it on other systems). One day one of the guys who was shuffling stuff back and forth between MiniUnix on a PDP-11/40 and our main 11/45 UNIX came to me with his RK05 file system corrupted. I found that the superblock was corrupted. With some painstaking comparison to another RK05 superblock, I reconstituded it enough to run icheck -s etc.. and get the thing back. What I had found was that the output of the “mount” command had been written on the superblock. WTF? I said, how did this happen. Interrogating the user yielded the fact that he decided he didn’t want to see the mount output so he closed file descriptor one prior to invoking mount. Still it seemed odd. At JHU we had lots of people with removable packs, so someone had modified mount to run setuid (with the provision of only allowing certain devices to be mounted certain places). At his point we had started with the idea of putting volume labels in the superblock to identify the pack being mounted. Rather than put the stuff in the kernel right away, Mike Muuss just hacked reading it from the super block in the usermode mount program so that he could put the volume label in /etc/mtab. Now you can probably see where this is headed. It opens up the disk, seeks to the pack label in the superblock and reads it (for somereason things were opened RW). Then the output goes to file descriptor 1 which just happens to be further in the superblock. I figured this out. Fixed it and told Mike about it. I told him there were probably other setuid programs around that had the problem and asked if it was OK if I hacked on things (at the time I yet was not trusted with the root password). He told me to go ahead, knock yourself out. Well I spent the evening closing various combinations of file descriptors and invoking setuid programs. I found a few more and noted them. After a while I got tired and went home. The next day I came in and looked through our paper logbook that we filled out anytime the machine was shutdown (or crashed). There was a note from two of the other system admins saying they had shut the system down to rebuild the accounting file (this was essentially the shadow password file and some additional per-user information not stored in /etc/passwd). The first 8 bytes were corrupted. Oh, I say, I think I might know how that happened. Yeah, we thought you might. Your user name was what was written over the root entry in the file. The passwd changing program was one of the ones I tested, but I hadn’t noticed any ill-effects for it at the time.

2 years, 3 months

I've just come across some old Unix Sources

by David Barto

Notably: 32v_usr.tar.gz and sys3.tar.gz. I’ve not unpacked the tar files. If someone would like more detail about the contents I’ll produce a TOC offline for them. David

2 years, 3 months

Earliest UNIX Workstations?

by Paul Ruizendaal

As a result of the recent discussion on this list I’m trying to understand the timeline of graphical computing on Unix, first of all in my preferred time slot ’75 -’85. When it comes to Bell Labs I’m aware of the following: - around 1975 the Labs worked on the Glance-G vector graphics terminal. This was TSS-516 based with no Unix overlap I think. - around the same time the Labs seem to have used the 1973 Dec VT11 vector graphics terminal; at least the surviving LSX Unix source has a driver for it - in 1976 there was the Terak 8510; this ran primarily USCD pascal, but it also ran LSX and/or MX (but maybe only much later) - then it seems to jump 1981 and to the Blit. - in 1984 there was MGR that was done at Bellcore Outside of the labs (but on Unix), I have: - I am not sure what graphics software ran on the SUN-1, but it must have been something - Clem just mentioned the 1981 Tektronix Magnolia system - Wikipedia says that X1 was 1984 and X11 was 1987; I’m not sure when it became Unix centered - Sun’s NeWS arrived only in 1989, I think? Outside of Unix, in the microcomputer world there was a lot of cheap(er) graphics hardware. Lot’s of stuff at 256 x 192 resolution, but up to 512 x 512 at the higher end. John Walker writes that the breakout product for Autodesk was Interact (the precursor to AutoCAD). Initially developed for S-100 bus systems it quickly moved to the PC. There was a lot of demand for CAD at a 5K price point that did not exist at a 50K price point.

2 years, 3 months

Re: Setting up an X Development Environment for Mac OS

by jnc＠mercury.lcs.mit.edu

> From: Lars Brinkhoff > It's my understanding it was started by Bob Scheifler of the CLU group. Yes, that's correct. (Bob's office was right around the corner from me - although I had very little knowledge of what his group was up to; I was too busy with other things.) I have this vague memory that his version was actually written in CLU? Can that be correct? It would make sense, since that group was so focused on CLU - but maybe not, see below. X must have been done after LCS got the 750 farm (on which we ran 4.1c, to start with) - although I don't know what kind of terminals they were using to run X on - we didn't have any bit-mapped displays on them, I'm pretty sure. Although maybe it was later, once Micro-Vaxes appeared? I have this vague memory that it was based (perhaps only in design, not code re-use) on a window system done at Stanford {looks}; yes, W (hence 'X'): https://en.wikipedia.org/wiki/W_Window_System The X paper listed there: https://dl.acm.org/doi/pdf/10.1145/22949.24053 doesn't say anything about the implementation, so maybe that vague memory/assumption that I had that it was originally written in CLU is wrong. Liskov's 'History of CLU' paper, which lists things done in CLU, doesn't mention it, so I must have been confused? Do any of the really early versions of X (and W) still exist? Noel

2 years, 3 months

[off-topic] Anyone still using USENET?

by arnold＠skeeve.com

Hi. I've been using trn for decades to read a very few USENET groups. Until recently I've been using aioe.org as my NNTP server but it seems to have gone dark. Before that I used eternal-september.org, but when I try that I now get: | $ NNTPSERVER=news.eternal-september.org trn | Connecting to news.eternal-september.org...Done. | | Invalid (bogus) newsgroup found: comp.sys.3b1 | | Invalid (bogus) newsgroup found: comp.sources.bugs | | Invalid (bogus) newsgroup found: comp.misc | | Invalid (bogus) newsgroup found: comp.compilers | .... And those all are (or were!) valid groups. If anyone has suggestions for a good free NNTP server, please let me know. Privately is fine. I'm at a bit of a loss otherwise. Thanks, Arnold

2 years, 3 months

reading historic magnetic tapes

by Steve Simon

i worked for some years on video and film archive restoration. baking old, badly stored magnetic tapes prior to reading them is a common practice. my favourite was a story of a rock band (i think the stones) who wanted to play an old 24 track master tape but discovered it seemed to be stuck together. there is a nasty affliction of mag tapes called sticky vinegar syndrome, so they did the right thing and sent a section of tape for analysis. the results came back: the tape had suffered impregnation with “vodka and coke”. some things never change. -Steve

2 years, 3 months

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TUHS January 2023