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2555 discussions

very strange DNS errors
by Trevor Cordes 12 Jun '16

12 Jun '16

Some recurring email bounces have tipped me off to a really strange DNS issue on the boxes I admin. I really need help on this as it's impacting a real customer in a real way: delayed emails. Often, and somewhat randomly, DNS will fail to resolve a domain. Sometimes it will fail to resolve it for >4 hours and trigger a diagnostic bounce from my sendmail. When I run tests at the command line (dig) on the domains in question (the ones I've seen in email bounces) I will often very quickly get a resolve failure, but usually 5s later another dig to the same domain will resolve 100% ok! Every box I am testing on has a similar config with BIND named 9.10 (9.8 on one box) running as the local recursive resolver. /etc/resolv.conf on all is 127.0.0.1. So that means every lookup that isn't cached is going to the root NS's. When it fails to resolve, named.log logs an entry like: 20-Apr-2016 00:37:28.276 query-errors: debug 1: client 127.0.0.1#33971 (artscouncil.mb.ca): query failed (SERVFAIL) for artscouncil.mb.ca/IN/A at query.c:7769 20-Apr-2016 00:37:28.276 query-errors: debug 2: fetch completed at resolver.c:3658 for artscouncil.mb.ca/A in 0.215778: SERVFAIL/success [domain:artscouncil.mb.ca,referral:1,restart:3,qrysent:2,timeout:0,lame:0,neterr:2,badresp:0,adberr:0,findfail:0,valfail:0] For manual tests it only logs one, for the real-life sendmail problem ones, I'll see dozen/hundreds of the same thing trying hour after hour (usually around the sendmail queue retry times). One of my boxes is *extremely* well connected in the US, and while it seems to have errors slightly less often, it still has them. All the rest are on various levels of Shaw or MTS, res or business. This seems to have just started popping up maybe 6 months ago. It feels like it's getting worse. I've setup an easy test, on the actual domains with the most problems: rndc flush dig +short sportmanitoba.ca dig +short gymcan.org dig +short brandoneagles.ca dig +short interactivegym.org dig +short artscouncil.mb.ca rndc flush dig +trace sportmanitoba.ca dig +trace gymcan.org dig +trace brandoneagles.ca dig +trace interactivegym.org dig +trace artscouncil.mb.ca Maybe some others can run those tests on their boxes (but only if you're running BIND as caching resolver, which many/most people won't be). Here's where it gets interesting the +short tests I can get to fail at least 1 of the domains (at random) about 1/8 of the time! On at least 5 different boxes out there! But +trace has never failed once on any box or any domain. It's like +trace does something different, maybe slowing the process down or something, that allows it to always succeed. (Failure for the +short is a missing line in output, +trace you have to look at the domain/ip returned near the bottom.) So, is it just these particular domains?? Something wrong on their (DNS) side? Or is it more domains, not just these? Is there any way to diagnose what exactly is failing? I find it bizarre that *all* of these domains regularly go down for 4+ hours causing an email bounce!?! Or is there something horribly wrong on my BIND caching DNS servers? Perhaps they are slow, and I'm my BINDs are just not waiting long enough. Is there a way to tell BIND to be more patient waiting for DNS packets to come in? Maybe it's something regarding IPv6? (I'm doing this all in IPv4 and have no current interest in 6. And I'm only looking for A records.) I have packet traces of the above sample commands when the lookups fail, but I can't really figure out what it's doing, other than one boatload of traffic for a tiny dns query. I can provide a trace privately on demand if you think you can help. Even more odd, I never seem to have a problem with interactive things like web browsing. If this was a problem with all domains, I should see this in firefox all the time, but I don't. Maybe Firefox doesn't even obey resolv.conf and does its own thing, or retries heavily itself? I also checked to ensure my iptables aren't dropping packets related to this. Lastly, answers of "just use 8.8.8.8" aren't helpful because I also need to handle dynamic local, and in some cases, external DNS (often with multiple views), all in the same BIND/box (and I like uniformity across boxes for ease of admin). Sure, I could try another resolver, but I see no reason BIND can't be made to work, as it has for me for 20 years. And if this is a BIND bug, I want to submit it to help solve it. Thanks guys!

5 14

MUUG Meeting, June 14, 7:30pm -- Gentoo
by Gilbert Detillieux 08 Jun '16

08 Jun '16

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, June 14. The meeting topic for this month is as follows: Gentoo Eric Raine will be presenting on the Gentoo Linux Distribution. Differences in installation from Ubuntu will be covered. Also covered is how to configure installation of packages and update. Gentoo is a free operating system based on either Linux or FreeBSD that can be automatically optimized and customized for just about any application or need. RTFM: Terminal Control Commands Due to a recent influx of new and novice members, Trevor Cordes will be doing an RTFM instead of a daemon dash this month. The topic is something every *NIX user should master: terminal control commands (e.g. ^Z and ^L) and rudimentary job control. These little dual-key presses will streamline your terminal sessions and make you more efficient. You'll wonder how you ever got by without them! 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 1M28* (1st floor) Manitoba 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 -- Manitoba UNIX User Group E-mail: <gedetil(a)muug.mb.ca> c/o Gilbert E. Detillieux Web: http://www.muug.mb.ca/ University of Manitoba Phone: (204)474-8161 Winnipeg MB CANADA R3T 2N2 Fax: (204)474-7609

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Fedora upgrading
by Kevin McGregor 03 Jun '16

03 Jun '16

Does anyone know how upgrade-able Fedora is? Say, Fedora 21 -> 22 -> 23? What about skipping a version? Does that work, or must you go through intermediate versions? Or is it best just to re-install each time? Thanks, Kevin

5 6

LACP breaking ARP?
by Wyatt Zacharias 13 May '16

13 May '16

Following up on my question to the roundtable at Tuesday's meeting, I did some more troubleshooting yesterday, and traced the problem down to the LACP link between the switch and the backup appliance. Running packet captures on both the backup appliance and the windows client, I can see that ARP packets are being lost on the LACP link. When I ping from the windows client to the appliance, I see the arp request and reply at the appliance, but the reply never makes it to the windows client. Pinging the other direction, appliance to windows client I see the arp requests at the appliance, but they never make it to the windows client and go unanswered. The backup appliance only does LACP with XOR source+dest mac, so I configured the switch to match. If I change the load balance algorithm to anything else on the switch the link goes down entirely, so it appears to be the right choice. Could this be just a config problem with LACP? In any case, I gave up on LACP specifically and switched the appliance to use round-robin and left the ports un-bonded on the switch which is working fine. -- Wyatt Zacharias

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hardvare inventory systems ?
by Grigory Shamov 12 May '16

12 May '16

Hi All, Do you know if there is a free hardware inventory system for Linux that would automatically get HW changes from, say, lshw? To track things like disk and server replacements. -- Grigory Shamov Westgrid/ComputeCanada Site Lead University of Manitoba E2-588 EITC Building, (204) 474-9625

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embedded linux hw question
by Trevor Cordes 12 May '16

12 May '16

I'm still working on that embedded linux print server I've mentioned before. I've gotten it to power on, fans spin, nic blinks, hdd spins, hdd light blinks (but not as much as I'd like). But it doesn't talk on the network at all. I'm flying blind and it would be really handy if I could find a port on this thing to get serial console or vga out. Unfortunately, this thing is super proprietary and I can't get any google hits on relevant pcb part numbers. Maybe there's some standard pin naming someone out there knows? Here's the connectors I can find that look promising: 10-pin ISPJTAG (google says it's for flash programming) 10-pin SX (no idea, but I tried putting a serial on it, nada) 14-pin P1 (no pins, just holes) 34-pin unlabelled there are also a few 2-pin jumper connectors: ICEBOOT MFG0 MFG1 SMBUS (no pins) RST Are any of these remotely useful for getting console or vga? It really seems like I'm getting somewhere but linux isn't booting completely, that's my guess. Looks like it's embedded Intel CPUs. The company that made the PCB is "Electronics for Imaging", from 2001. (It goes with a very expensive printer.)

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Get The Edge
by North Forge 11 May '16

11 May '16

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Humble Bundle - only until noon today!
by Trevor Cordes 11 May '16

11 May '16

(Or maybe 1pm...) As discussed at the meeting last night, the No Starch Press 13-book ebook name-your-own-price Humble "Hacking" Bundle is available here: https://www.humblebundle.com/books/no-starch-hacking-books And I wanted to drop a note to let everyone know that if you're interested, you must act *now* because the deal ends at around noon today (May 11). All the details are at the web site above. (Aside: Maybe these bundles are a good idea for publishers/charities; this one has grossed almost $1M US so far!)

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IPv6 in Manitoba
by Vijay Sankar 03 May '16

03 May '16

I have had an IPv6 tunnel working through Hurricane Electric since 2011 or so but increasingly it is not usable due to changes in security stances at the destination sites. Ideally I would like to have a /48 subnet with addresses that allow use of DNS etc.. Checked with tech support at MTS and Shaw but both said IPv6 is not available through them. So I am wondering what others are doing. Really appreciate any advice or suggestions about IPv6 providers in Winnipeg. Thank you very much, Vijay -- Vijay Sankar, M.Eng., P.Eng. ForeTell Technologies Limited vsankar(a)foretell.ca

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MUUG Meeting, May 10, 7:30pm -- Double Daemon Dash
by Gilbert Detillieux 03 May '16

03 May '16

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, May 10. The meeting topic for this month is as follows: Now in 3-D! (Double Daemon Dash) In this case we mean that this meeting will feature a Double Daemon Dash (DDD) instead of one DD and one regular presentation: In Wyatt's Daemon-Dash segment he will be presenting the Squid caching proxy server daemon. Squid is a full featured proxy daemon with support for http, https, and ftp. Wyatt will show the quickest way to have Squid up and running on a new server, and how to keep it secure. Paul Sierks will present on DavMail. 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 3M60* (3rd floor) Manitoba 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 -- Manitoba UNIX User Group E-mail: <gedetil(a)muug.mb.ca> c/o Gilbert E. Detillieux Web: http://www.muug.mb.ca/ University of Manitoba Phone: (204)474-8161 Winnipeg MB CANADA R3T 2N2 Fax: (204)474-7609

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