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Xv6, a simple Unix-like teaching operating system

pdos.csail.mit.edu

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Re: Xv6, a simple Unix-like teaching operating system

#81

Post by ori_b »

pjmlp wrote: post #76
sham1 wrote: post #70

Earlier quoted context omitted.

The irony here is that both SerenityOS and Redox are UNIX-like. Of course in their design, they're not purely like most other UNIXen, but they also don't stray away too far.

They offer a POSIX like API on top, which isn't the same thing, as the key APIs, and overall system architecture, are something else. Also mostly because as it happens in most hobby projects, people keep wanting to replicate GNU due to the existing software, thus keeping the UNIX cycle alive.

The POSIX API comes with a large number of warts and constraints, and requires a great deal of specific machinery to support.

Re: Xv6, a simple Unix-like teaching operating system

#82

Post by vkazanov »

pjmlp wrote: post #73
vkazanov wrote: post #60

Earlier quoted context omitted.

Android, SteamOS, WebOS and all the numerous Linux-based projects, mostly show that the world needs a stable target platform everybody can do a meaningful contribution to (and then make sure nobody steals the work later). Linux literally ate the world with its POSIX-compatible open-source proposition. I don't have a single device without Linux at home, and this includes a NAS, 5 notebooks, 1 PC, a handheld gaming con…

Just wait until the Linux founding fathers are no longer around. Try to write Linux POSIX code for Android, WebOS, and ChromeOS apps, and see how many normies will buy your wonderfull app. Free beer ate the world, everyone likes free beer, even it is warm.

Yes, free as in beer and free as in freedom. No complicated licensing, code open for change, any scale, any use-case.

Hard to compete against with all these "license per working space" or "tcp stack not included" or "no code for you" of the usual competitors.

> Just wait until the Linux founding fathers are no longer around.

Yes, things change all the time. People come and go. Just as companies do.

Re: Xv6, a simple Unix-like teaching operating system

#83

Post by anthk »

asystole wrote: post #64
user20180120 wrote: post #52

Plan9 was/is used at a university is Spain for teaching

Bracing myself for the next generation of self-important monochrome tech ‘zines coming out of Spain

I wish, but most IT manuals everywhere are in English. But this is IT/CS, so using English at least to being able to read technical articles it's mandatory. Nothing too difficult, as my non-tech SO (native Spanish speaker) had read novels written in British English and to me that prosody and style it's hell compared to either an Stephen King or a Preston&Child one.

Re: Xv6, a simple Unix-like teaching operating system

#84

Post by anthk »

pjmlp wrote: post #73
vkazanov wrote: post #60

Earlier quoted context omitted.

Android, SteamOS, WebOS and all the numerous Linux-based projects, mostly show that the world needs a stable target platform everybody can do a meaningful contribution to (and then make sure nobody steals the work later). Linux literally ate the world with its POSIX-compatible open-source proposition. I don't have a single device without Linux at home, and this includes a NAS, 5 notebooks, 1 PC, a handheld gaming con…

Just wait until the Linux founding fathers are no longer around. Try to write Linux POSIX code for Android, WebOS, and ChromeOS apps, and see how many normies will buy your wonderfull app. Free beer ate the world, everyone likes free beer, even it is warm.

Alan Cox will do it fine, and the rest of the people have similar skills on GNU licensing and such.

Re: Xv6, a simple Unix-like teaching operating system

#85

Post by kragen »

js8 wrote: post #66
kragen wrote: post #63

Earlier quoted context omitted.

like what?

For example, on z/OS, the whole disk storage subsystem (SMS, but there is more) is separate from the MVS (kernel). Security is also externalized in RACF server (in fact there are alternate products from non-IBM vendors). You can run multiple TCP/IP stacks, which are also running in their own address spaces. Sysplex serialization has its own address space. All the address spaces involved in the operating system are co…

i don't know enough about it to have an opinion. thanks!

Re: Xv6, a simple Unix-like teaching operating system

#86

Post by z3phyr »

pjmlp wrote: post #38
nialv7 wrote: post #12

Why Unix v6? Why teach with a 50 years old design? I feel to teach the fundamentals of an operating system, i.e. scheduling, IPC, address space management, a microkernel design would be better.

That is how we end with students always cloning UNIX on their projects, instead of going alternative roots like Redox or SerenityOS.

Or maybe something like a lisp machine or a smalltalk os?

Re: Xv6, a simple Unix-like teaching operating system

#87

Post by kragen »

shawn_w wrote: post #46
kragen wrote: post #21

Earlier quoted context omitted.

a lot of people agree with you, which is why minix exists (though their source control system just fell offline this year), but none of windows nt, linux, os/360, and even really macos/ios are microkernel designs. sel4 and the other l4 variants are, and so is qnx, and linuxcnc runs linux under a microkernel, and xen is kind of a microkernel if you look at it funny, so we're definitely seeing significant mainstream us…

>minix exists (though their source control system just fell offline this year), https://git.minix3.org/index.cgi seems online?

this started failing, i think, last week:

    : ~; git clone git://git.minix3.org/minix.git 
    Cloning into 'minix'...
    fatal: Could not read from remote repository.

    Please make sure you have the correct access rights
    and the repository exists.

Re: Xv6, a simple Unix-like teaching operating system

#88

Post by kelsey98765431 »

hnthrowaway0328 wrote: post #68
kelsey98765431 wrote: post #50

Earlier quoted context omitted.

For a good look at the development of the NT kernel, read the book show stopper from 1996. It is correct that Dave Cutler did lead a number of projects inside DEC including projects related to VMS, the only inheritance the Microsoft New Technology kernel received from VMS was spiritual at the design and architecture levels. Dave was already in the process of a major overhaul or successor to VMS when his team was show…

I am reading the book, now that you mentioned. I only reach the part when David was hired by Microsoft though. Actually I'm super interested in his earlier works in Dupont and DEC as they paved the way. I took him as an inspiration. His “What I really wanted to do was work on computers, not apply them to problems.” rings so true with me, and he as a natural leader also makes me look up to him.

Difficult realm for me to investigate myself. I have found that better than any book is to pull old VMS images out and get them up on a SIMH/Vax emulator and poke around! It's a quite laborious process and documentation of the process is sparse, last time I ended up using the Computer History Museum remote access program to interact with ancient VMS.

To actually learn how to use the thing I ended up diving deep into textfiles.com archives for references to VMS and got the hang of the basics enough to start learning via the online (built in) documentation.

I would also point you towards usenet archives if you want to learn more about the development history of VMS, what what i have been able to piece together it was really rock solid and loved and quite a shame that "open"VMS is mostly just a legacy compatibility licensing agreement and the technology is in a bit of a glacial deep freeze.

The fact that every file on the entire OS had version control - by default - before 1990... that blows me away and I feel like there's so many beautiful secrets to learn from this codebase. I always imagined it would be written in some abstract arcane language, when I learned it was in C i got a bit scared knowing what microsoft calls C has very little resemblance to how C is typically used on unix likes, and with the knowledge that many VAX admins dumped VMS for BSD I was quite afraid I may be out of my element.

I was surprised to find the C library is essentially just posix, I felt pretty much completely at home on VMS compared to any version of windows I have had to write C for. Pleasant experience, shame what happened to it, wish there was more about its story told in an authoritative context like a book.

If you stumble across anything nifty please feel free to share I may come back and read this read again someday.

Cheers

Re: Xv6, a simple Unix-like teaching operating system

#89

Post by linguae »

z3phyr wrote: post #86
pjmlp wrote: post #38

Earlier quoted context omitted.

That is how we end with students always cloning UNIX on their projects, instead of going alternative roots like Redox or SerenityOS.

Or maybe something like a lisp machine or a smalltalk os?

I would LOVE to build a modern-day operating system using a high-level programming language, even if it were just a pedagogical toy. I love Unix, but it’s not (and shouldn’t be) the final word on OS design.

In the meanwhile, Project Oberon from the late Niklaus Wirth (http://www.projectoberon.net/) is a good example of a pedagogical operating system (and programming language) that isn’t Unix. Project Oberon was heavily influenced by the Cedar and Mesa projects at Xerox PARC.

Re: Xv6, a simple Unix-like teaching operating system

#90

Post by darby_nine »

pjmlp wrote: post #40
kragen wrote: post #22

Earlier quoted context omitted.

apple started with mach, which was a microkernel, and linked basically all of the freebsd kernel into it, morphing it from a microkernel operating system into a monolithic operating system i agree that monolithic kernels are unpleasant and brittle, but unfortunately they don't actually seem to be obsolete

NeXT you mean. Additionally, Apple has a long term roadmap to fix that design decision, hence why they are killing one kernel subsystem at a time, moving them into userspace, with one year given for the developers to adopt each of them, after being made available as the new way. Finally, it is kind of ironic that systems that have doubled down on monolithic kernels, are now used to run an endless pile of containers a…

> hence why they are killing one kernel subsystem at a time, moving them into userspace, with one year given for the developers to adopt each of them, after being made available as the new way.

Notably they aren't exposing most of the functionality, it wouldn't be possible to e.g. implement NFS or 9p with the userspace filesystem thing they've been pushing. They're basically just shutting users out from their own computer....

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