August 2015 - wlug - list.wlug.org.nz

Multics vs Unix
by Lawrence D'Oliveiro 12 Nov '15

12 Nov '15

I’ve been reading the introductory “Multics Concepts and Utilization” book <http://bitsavers.trailing-edge.com/pdf/honeywell/multics/F01_multicsIntroCo…> over at Bitsavers. Multics (the “MULTiplexed Information and Computing Service”) was, for its time, an extremely ambitious operating system project. It was first introduced in 1965, in the form of a series of papers at the AFIPS Fall Joint Computer Conference of that year <http://www.computer.org/csdl/proceedings/afips/1965/5066/00/index.html>. Of course, it took far too long (7 years) to reach production quality. In that time, a small group of researchers at AT&T Bell Labs grew tired of waiting, and decided to create their own, less ambitious system, which they called “UNIX” as a tongue-in-cheek homage to “Multics”. And the rest, as they say, is history. But, nevertheless, Multics remained an influential system. There are even some present-day fans of it gathered at <http://multicians.org/>. Apparently they have got the OS booting on an emulator of the original GE 645 hardware. Though it was mostly written in a high-level language (PL/I), Multics was never a portable OS; to support its advanced virtual-memory and security features, it required special processor hardware support which was not common in those days. Even today, Multics has some features which can be considered innovative and uncommon. It may be true that, for example, SELinux can match all of its security capabilities and more. But some aspects of its file-protection system seem, to me, to make sharing of data between users a bit easier than your typical Linux/POSIX-type system. For a start, there seems to be no concept of file “ownership” as such. Or even of POSIX-style file protection modes (read/write/execute for owner/group/world). Instead, all file and directory access is controlled via access-control lists (ACLs). Directories have a permission called “modify”, which effectively gives a matching entity (user, group, process) owner-type rights over that directory; except that more than one entity can have that permission at once. Thus, a group of users working on a common project can all be given this “modify” access to a shared directory for that project, allowing them all to put data there, read it back again, control access to it, delete it etc on a completely equal basis. Contrast this with POSIX/Linux, where every file has to have exactly one owner; even if they create that file in a shared directory, it still gives the creating user a special status over that file, that others with write access to the containing directory do not have. (Multics also offers a separate “append” permission, that allows the possessor to create an item in a directory, without having the ability to remove an item once it’s there.) One radical idea introduced in Unix was its profligate use of multiple processes. Every new command you executed (except for the ones built into the shell) required the creation of a new process, often several processes. Other OSes tended to look askance at this; it seemed somehow wasteful, perhaps even sinful to spawn so many processes so readily and discard them so casually. The more conventional approach was to create a single process at user login, and execute nearly all commands within the context of that. There were special commands for explicitly creating additional processes (e.g. for background command execution), but such process creation did not simply happen as a matter of course. Gradually, over time, the limitations of the single-process approach became too much to ignore, and the versatility of the Unix approach won over (nearly) everybody. Multics, however, is of the old school. More than that, the process even preserves global state, including static storage, in-between runs of programs, and this applies across different programs, not just reruns of the same one. For example, in FORTRAN, there is the concept of a “common block”. If you run two different programs that both refer to the same common block, then the second one will see values left in the block by the first one. To completely reinitialize everything, you need to invoke the “new_proc” command, which effectively deletes your process and gives you a fresh one. One common irritation I find on POSIX/Linux systems is the convention that every directory has to have an entry called “.”, pointing to itself, and one called “..”, pointing to its parent. This way these names can be used in relative pathnames to reach any point in the directory hierarchy. But surely it is unnecessary to have explicit entries for these names cluttering up every directory; why not just build their recognition as a special case into the pathname-parsing logic in the kernel, once and for all? That way, directory-traversal routines in user programs don’t have to be specially coded to look for, and skip these entries, every single time. Multics doesn’t seem to have this problem. An absolute pathname begins with “>” (which is the separator for pathname components, equivalent to POSIX “/”), while a relative pathname doesn’t. Furthermore, a relative pathname can begin with one or more “<” characters, indicating the corresponding number of steps up from the current working directory. Unlike POSIX “..”, you can’t have “<” characters in the middle of the pathname, which is probably not a big loss. It is interesting to see other features which are nearly, but not quite, the same as, corresponding features in Unix. For example, there is a search path for executables, to save you typing the entire pathname to run the program. However, this does not seem as flexible as the $PATH environment-variable convention observed by Unix/POSIX shells. In particular, it does not seem possible to remove the current directory from the search path, which we now know can be a security risk. Another one is the concept of “active functions” and “active strings”. These allow you to perform substitutions of dynamically-computed values into a command line. However, they are not as general as the Unix/POSIX concept of “command substitution”, where an entire shell command can supply its output to be interpolated into another command. Instead of having a completely separate vocabulary of “active functions” which can only be used for such substitutions, Unix/POSIX unifies this with the standard set of commands, any of which can be used in this way. There are other features of Multics that others more familiar with it might want to see mentioned (the single-level store concept, where “everything is a memory segment”, versus Unix “everything is a file”? I/O redirection based on “switches”—symbolic references to files, versus Unix integer “file descriptors”?). But then, this long-winded essay would become even longer-winded :). So if you are interested in this particular piece of computing history, feel free to follow up the links above. In summary, Multics is very much a museum piece, not something you would want to use today for regular work—not in its original form. But I think there are still one or two ideas there that we could usefully copy and adapt to a present-day OS, particularly a versatile one like Linux.

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LILO Development Coming To An End
by Lawrence D'Oliveiro 01 Sep '15

01 Sep '15

<http://phoronix.com/scan.php?page=news_item&px=LILO-Bootloader-EOY> Is anybody still using LILO (the “LInux LOader”)? That was the Linux-specific bootloader from the early days, before GRUB (the “GRand Unified Bootloader”) came on the scene. I remember one difference was that LILO compiled its configuration into the bootloader binary at installation time. That way, if you made any errors in the configuration, you usually discovered that immediately. Whereas with GRUB, you only found this out when your machine failed to boot. Though with GRUB 2 commonplace nowadays, I haven’t felt the need to configure anything as yet. It seems smart enough to figure it out all by itself. :)

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"Hack" Typeface Is Open Source, Easy On the IDEs
by Peter Reutemann 31 Aug '15

31 Aug '15

"Ars Technica writes that "At SourceFoundry.org this week, programmer Chris Simpkins debuted the 2.0 version of Hack, an open-source typeface designed specifically for use in source code." The revamped font is" characterized by a large x-height, wide aperture, and low contrast design in order to be "highly legible" at common coding text sizes," and the font specimen shows how legible it is right down to downright tiny sizes, though Simpkins says the sweet spot is between 8 and 12 pixels. " -- source: http://developers.slashdot.org/story/15/08/30/1733217 Very subtle differences in comparison to "monospace", from a quick comparison: - the dash "-" is longer - the "*" has five points rather than six - the "i" looks more like an "l" (not so sure about this change, though) - the stroke inside the zero is more pronounced Using Hack in a terminal seems a bit clearer than monospace. Here's a howto for Mint on installing a new font: http://community.linuxmint.com/tutorial/view/29 Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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Fake EFF site serving espionage malware was likely active for 3+ weeks
by Peter Reutemann 31 Aug '15

31 Aug '15

"A spear-phishing campaign some researchers say is linked to the Russian government masqueraded as the Electronic Frontier Foundation in an attempt to infect targets with malware that collects passwords and other sensitive data." -- source: http://arstechnica.com/security/2015/08/fake-eff-site-serving-espionage-mal… Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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THE MAGPI ISSUE 37 - SEPTEMBER 2015
by Peter Reutemann 30 Aug '15

30 Aug '15

Featured in The MagPi Issue 37: * Build a Raspberry Pi digital home Eight projects to build tomorrow’s home, today * Stream live from your PC Use the hottest PC software anywhere in your house * Build a fridge monitor Everyday engineering brought to life with your Pi * Build a computer vision sequencer Mike Cook continues his Pi Bakery project series * The Fallout Pip-Boy How one man made sci-fi fact, just in time for Fallout 4! -- source: https://www.raspberrypi.org/magpi/issues/37/ PDF can be downloaded for free. Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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The NZ Herald’s Data Blog
by Lawrence D'Oliveiro 30 Aug '15

30 Aug '15

Discovered this through a mention on the “Media Watch” program on RNZ National <http://www.radionz.co.nz/national/programmes/mediawatch/audio/201762824/min…>. Harkanwal Singh is a “data journalist”, who uses data analysis techniques to put together news stories. His group has already published some interesting analyses, such as broadband affordability, school deciles, traffic crashes and other things. <http://www.nzherald.co.nz/data-blog/news/headlines.cfm?c_id=1503710>

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Linux Kernel 4.2 Released
by Peter Reutemann 30 Aug '15

30 Aug '15

"The Linux 4.2 kernel is now available. This kernel is one of the biggest kernel releases in recent times and introduces rewrites of some of the kernel's Intel Assembly x86 code, new ARM board support, Jitter RNG improvements, queue spinlocks, the new AMDGPU kernel driver, NCQ TRIM handling, F2FS per-file encryption, and many other changes to benefit most Linux users." -- source: http://linux.slashdot.org/story/15/08/30/1949211 Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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KDE Is Broken In Debian Unstable
by Lawrence D'Oliveiro 29 Aug '15

29 Aug '15

Looks like KDE is in the middle of a major transition in Debian Unstable at the moment. Yesterday I did an update on my backup machine, and found that I had no window manager after logging into the GUI. This morning I did another update, and was presented with a new “flat” look after a GUI login. Checking my package versions, I believe I have some parts of KDE 5, but not all (yet). I might do another update this evening. Luckily my backup machine can still fulfil most of its functions without a GUI...

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Learn FPGAs With a $25 Board and Open Source Tools
by Peter Reutemann 27 Aug '15

27 Aug '15

"Hackaday has a 3 part tutorial with videos of using open source tools with a cheap ($25) FPGA board. The board isn't very powerful, but this could be the 'gateway drug' to FPGAs for people who don't want to spend hundreds of dollars and install 100s of megabytes of software and license keys just to get their feet wet. The videos are particularly good--like watching them over their shoulder. As far as I know, this is the only totally open source FPGA toolchain out there." -- source: http://hardware.slashdot.org/story/15/08/27/226232 Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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Ddrescue-GUI: Front-End for Ddrescue Command-line Tool
by Peter Reutemann 27 Aug '15

27 Aug '15

"DDRescue-GUI is a simple GUI application written in Python 2 and designed to provide users with an easy-to-use GUI (Graphical User Interface) front-end for the awesome GNU ddrescue command-line tool which dedicated to recovering data from hard drive, USB flash drive, cd, dvd corrupt." -- source: http://ubuntuportal.com/2015/08/ddrescue-gui-ubuntu.html Cheers, Peter -- Peter Reutemann Dept. of Computer Science University of Waikato, NZ +64 (7) 858-5174 http://www.cms.waikato.ac.nz/~fracpete/ http://www.data-mining.co.nz/

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