- Roundtable - muug.ca

Re: [RndTbl] Really old MTS Internet drop?
by Adam Thompson 05 Feb '14

05 Feb '14

Actually, vampire taps were fairly easy to handle. The big problem was putting the AUI transceiver near each station in a way the user couldn't damage it accidentally. And yeah, running the backbone cable was a *bit* of a pain! -Adam On Feb 5, 2014 10:59 AM, Hartmut W Sager <hwsager(a)marityme.net> wrote: > > I do consider it quite possible that this is simply a 10Base-2 NIC, and that MTS supplied such NIC's at one time (to match some ancient DSL modem), even though I don't distinctly remember this from my MTS past. A hub isn't needed - 10Base-2 has all the stations (computers, etc.) along a linear cable with T-connectors at each of them, even the two end units, and a terminating resistor on the otherwise open-ended T-connector at each of the two ends. > > Man, I hated wiring the connectors onto those 10Base-2 cables! Anyone out there old enough to have handled the even older 10Base-5 stuff? You gotta love RJ-45! > > Hartmut Sager > > > On 5 February 2014 09:50, Colin Stanners <cstanners(a)gmail.com> wrote: >> >> Likely: PC TV-capture card, or they're really confusing an ethernet cable. >> Very unlikely: ancient 10base-2 NIC to a hub somewhere with their DSL modem. >> >> >> On Wed, Feb 5, 2014 at 8:40 AM, Kevin McGregor <kevin.a.mcgregor(a)gmail.com> wrote: >>> >>> Friends of my parents have had MTS Internet service for a decade or more (probably more). >>> >>> They told me that they have a coax cable in the room with their computer (an IBM Pentium 4 3.0 GHz, to give you an idea of the age of this setup; they had MTS Internet service before that in an older computer) AND that this coax cable plugs directly into their PC.Has anyone seen this sort of setup? I didn't look at it myself; this is just what I got from them over the phone just now. >>> >>> Are they mistaken, or did MTS in the past provide a PC card with a coax connector for Internet access? It's possible that they didn't recognize an Ethernet cable, but I did explicitly ask if it was connected to the computer with a screw-on type connector which they confirmed it was. >>> >>> Kevin >>> >>> _______________________________________________ >>> Roundtable mailing list >>> Roundtable(a)muug.mb.ca >>> http://www.muug.mb.ca/mailman/listinfo/roundtable >>> >> >> >> _______________________________________________ >> Roundtable mailing list >> Roundtable(a)muug.mb.ca >> http://www.muug.mb.ca/mailman/listinfo/roundtable >> >

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MUUG Meeting, Feb 11, 7:30pm -- Raspberry Pi Real Time Clock
by gedetil＠cs.umanitoba.ca 04 Feb '14

04 Feb '14

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, February 11. The meeting topic for this month is as follows: Raspberry Pi Real Time Clock Wyatt Zacharias will be presenting the Raspberry Pi along with a Real Time Clock circuit. "A real-time clock is a computer clock that keeps track of the current time. Although the term often refers to the devices in personal computers, servers and embedded systems, RTCs are present in almost any electronic device which needs to keep accurate time." For this month's RTFM topic, Trevor Cordes will be presenting the history command, as found in (for example) bash(1) or tcsh(1). The group holds its general meetings at 7:30pm on the second Tuesday of every month from September to June. (There are no meetings in July and August.) Meetings are open to the general public; you don't have to be a MUUG member to attend. ***************************************************************** Please note our *NEW* meeting location for this month: Room 1L08, Lockhart Hall, University of Winnipeg, entrance on Ellice Ave. between Spence St. and Balmoral St. Parking is available on the surrounding streets and in the lots on nearby streets. Look for signage once you're at the building, or ask a security guard. ***************************************************************** For more information about MUUG, and its monthly meetings, check out their Web server: http://www.muug.mb.ca/ Help us promote this month's meeting, by putting this poster up on your workplace bulletin board or other suitable public message board: http://www.muug.mb.ca/meetings/MUUGmeeting.pdf -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.mb.ca> Manitoba UNIX User Group Web: http://www.muug.mb.ca/ PO Box 130 St-Boniface Phone: (204)474-8161 Winnipeg MB CANADA R2H 3B4 Fax: (204)474-7609

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Re: [RndTbl] strange race condition on file entries
by Trevor Cordes 03 Feb '14

03 Feb '14

But after programming heavily in Perl for 22 years (!!!) I can safely say I pretty much have the quirks and syntax oddities nailed. This is the first time in a long time something like this one has bit me, and it's understandable because I rarely use the glob op. If you don't like all the weirdness, the beauty of Perl is you can instead just program it as though it was C without malloc. I like choice. -------- Original message -------- From: Sean Walberg <sean(a)ertw.com> Date:2014/02/02 20:00 (GMT-06:00) To: Continuation of Round Table discussion <roundtable(a)muug.mb.ca> Subject: Re: [RndTbl] strange race condition on file entries While I will always manage my life by the three great virtues, I must thank you for reminding me why I gave up slinging Perl. DWIM and all the sigils drive a man to an early grave, or at least a lot of nights debugging. Sean On Sun, Feb 2, 2014 at 1:10 PM, Trevor Cordes <trevor(a)tecnopolis.ca> wrote: I forgot to post what *does* work. There are a few different ways. You can force the glob to return a list (hence no caching/iterating): if (!@{[<$prefix-*>]}) { That's sure ugly, but it makes sense. [] forces the <> to return list and turns it into an anon array-ref. @ then derefs. {} is required by the parser to make sense of it all. !@ then does its normal thing of meaning "if there are zero elements in this array". You could also force it to list by assigning to an array: if (!(@a=<$prefix-*>)) { But I hate using temp vars when we don't need to; when the results are throwaway. Strangely, using the normal "we want a list" syntax of just putting () around the expression doesn't work in this case. I'm not sure why: if (!(<$prefix-*>)) { # doesn't work Also strangely, while perl has a "scalar" function to force a scalar (non-list) result, it doesn't have a "list" or "array" function to force a list. The scalar docs say list isn't necessary as it's usually the default/implied or can be forced with (). Woops, looks like I found a corner case. Ya, I could have been certain everything worked in the first place by doing opendir and iterating through the results, like one would in C, but the whole purpose of using perl is to do as much as possible in as few characters and lines. Laziness is the #1 programmer virtue, according to L.Wall and R.Schwarz. _______________________________________________ Roundtable mailing list Roundtable(a)muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable -- Sean Walberg <sean(a)ertw.com> http://ertw.com/

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CF/SD/MMC readers under Linux
by Adam Thompson 03 Feb '14

03 Feb '14

I've noticed that many USB card readers are non-functional under Linux; according to the kernel developers, it's because relatively few of them implement the USB removable block storage class (protocol) correctly. While there are lots of expensive card readers that work with Linux, finding cheap ones is challenging. I think, however, that I've found the ultimate *cheap* USB card reader that works with Linux: the "Tech-1 USB 2.0 CARD READER" at Dollarama. IIRC, it cost $2. You'll almost certainly want to get a USB A-A extension cable for $1 or $2 at the same time, since the card reader comes with a 1" cable... -- -Adam Thompson athompso(a)athompso.net

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strange race condition on file entries
by Trevor Cordes 03 Feb '14

03 Feb '14

I'm running into a strange race condition, that appears to me to be a Linux bug of some sort. I'm doing, perl pseudocode: system "process-file outputfileprefix" # does work and puts it in files named outputfileprefix-0, outputfileprefix-1, etc sleep 1; if (!<outputfileprefix-[0-9]*>) { warn "try #2\n"; sleep 2; if (!<outputfileprefix-[0-9]*>) { warn "try #3\n"; die; } } # do something on outputfile* For those that don't know <> is perl's glob op, which simply returns an array of all the files matching the glob. !<> is thus true if no files match the glob. What is happening is that 10-30% of the time, I get a "try #2" output. I haven't yet seen a try #3. Of course, having those retries (and sleeps) in there at all should not be required: I had to add them as I was seeing this program blow up in unexpected ways. process-file does not do anything async'ly, AFAIK. The final thing it does, the output that I need, is use the GD library to write a png file. Only after that does process-file exit. There are no threads or forks, unless GD is doing one, but even then the mini-program above should not return from system until all threads and (non-daemonized) forks are done. It appears the problem is process-file writes and closes a file, returns, yet the directory entry doesn't become visible to the calling script for 0 to 3 seconds! I was under the impression that such UNIX OS actions were guaranteed to occur reliably in sequence! Note, the fs I'm using is local and normal harddisk-based. It is not on NFS or SMB, which of course could show such results. Comments? Ideas?

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GD package?
by Kevin McGregor 21 Jan '14

21 Jan '14

I'm setting up a Ubuntu 10.04.4 LTS server at work for a client who plans to install something called "Stori" (an Oracle-ish thing, stori.orapub.com) The requirements FAQ on that site is vague, saying "You can install our product on any Linux server." Okay, so what else? "You will need the gd package; do rpm -q gd to ensure it's installed." That's for a Red Hat-derived distro presumably, so what's the equivalent for Debian/Ubuntu? The only package I found was php5-gd, which seems like overkill as it brings in a ton of other stuff. Is gd installed by default in Ubuntu 10.04?

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Treasure Chest
by Brock Wolfe 19 Jan '14

19 Jan '14

Alas I have to make room by doing some spring cleaning on my magazine collections. I hate to send these to recycling. Offered on first come first serve basis: - Circuit Cellar Magazines - major collection. - Linux Magazines - Maximum Linux magazines - Sys Admin magazines - Home Power Magazines - Servo Magazines Brock

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MitM on IMAPS?
by Trevor Cordes 19 Jan '14

19 Jan '14

I'm just wondering if it is possible for someone to MitM me in the following scenario and intercept plaintext traffic: dovecot imaps server with real thawte "quick" cert | imaps (ssl) | public wifi | android phone using imaps using "ssl" not "ssl (any cert)" option For instance, can a malicious hotspot use some sort of interception technique / spoofing and some sort of wildcard cert to trick my phone into negotiating SSL with it, which then does its own SSL to my dovecot server, thus MitM'ing me without me even knowing? I know in a web browser I'd normally be protected against that by looking at the URL in the address bar, or the green EV-cert graphics (or am I wrong in even that assumption)? How paranoid do I have to be? And is there any way to beat any shortcoming on Android, perhaps with a client cert or a way to tie the account to a single manually-specified server SSL cert?

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Re: [RndTbl] xargs with no command
by Trevor Cordes 18 Jan '14

18 Jan '14

On 2014-01-18 Adam Thompson wrote: > Other way 'round: xargs was the newline inserter, splitting a > WS-separated list into multiple lines. >From memory, it looked to me like xargs was a NL-eater, and only an EOL NL- appender. #cat > z a b c # xargs <z a b c *** note how the input is NL-sep, but the output is space-sep, just I think as in Kevin's RTFM. And the while loop was one line (one xargs call) per iteration. Of course, this is just from memory!

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Re: [RndTbl] xargs with no command
by Adam Thompson 18 Jan '14

18 Jan '14

Other way 'round: xargs was the newline inserter, splitting a WS-separated list into multiple lines. That's still the first time I'd ever seen xargs used like that! -Adam On Jan 18, 2014 12:54 AM, Trevor Cordes <trevor(a)tecnopolis.ca> wrote: > > As per Tuesday's meeting RTFM: > > ibm.com gave me the first hint: > If no command template appears on the command line, xargs uses echo by > default. > > Which then let me find it in Linux's man page: > ... and executes the command (default is /bin/echo) ... > > So they were basically using xargs as a newline-eater to combine all the > lines of the iteration into one. > _______________________________________________ > Roundtable mailing list > Roundtable(a)muug.mb.ca > http://www.muug.mb.ca/mailman/listinfo/roundtable

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