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For Pi users
by nev young 03 Aug '12

03 Aug '12

Something that may be of interest to both ALUG and 2600 members is this magazine (it's free) for the Raspberry Pi. The url is http://www.themagpi.com Nev

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LAN traffic sniffing/monitoring - good tools and methods - help wanted
by Chris Green 31 Jul '12

31 Jul '12

I want somehow (if it's possible) to monitor the packets going into and out of one ethernet address/MAC address on my LAN. I think it's currently plugged into a port on my 8-port Gigabit switch but I'm not absolutely sure of that. The LAN comprises a Draytek Vigor ADSL router talking to the outside world and a Linksys 8-port Gigabit router with most of my LAN systems plugged into that. I think a couple of the four ports on the ADSL router may be in use in addition to the one that connects to the 8-Port Gigabit switch. Is there any 'easy' way to monitor all traffic to/from one specific IP address on the LAN from my desktop computer or will the switches on the LAN prevent it seeing most of the traffic? Actually even being able to see all traffic between my desktop and the device I'm interested in would probably be sufficient as 'lack of traffic' might well be enough to tell me what I want to know. So what are the best/easiest packet sniffers to run on a desktop machine that would allow me to 'see' all traffic to/from a specific IP address? -- Chris Green

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2600 meeting at 18:00 on Friday the 3rd August.
by Viperfang 31 Jul '12

31 Jul '12

Quick heads up about this months Norwich 2600 meeting, more info at http://www.norwich2600.co.uk

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Xen and OOM killer
by Richard Lewis 30 Jul '12

30 Jul '12

Hi ALUG, I've been managing a Xen hypervisor for about nine months now and occasionally I get problems with DomUs running out of memory. The clients are all students and most of them are running WordPress blogs. The instances of OOM errors I've seen seem to be related to Apache and students serving up large image files. I'm thinking that this shouldn't really be happening; serving up a few ~1MB files shouldn't really be causing Apache to make the OS exhaust *all* available memory, should it? Even if it were servicing several requests simultaneously. Some details: * The host is a Dell PowerEdge x86_64 system with 32 GB RAM * The host OS is Debian 6.0 * We're running Xen 4.0.1 from Debian * The guests all run Debian 6.0 * Each guest has 15 GB of storage, 512 MB RAM, and 1 GB of swap * We currently have ~40 guests running Below is some console output from a DomU that suffered this problem earlier today. You can see that the OOM killer killed Apache. And I'm guessing it killed sshd too as I couldn't connect to the guest. I couldn't find any errors in Xen's logs. Any thoughts on what might be going on here? And come September we'll have a short window in which we could alter out setup. Any suggestions for better ways of providing virtual machines? Perhaps alternatives hypervisors? Or some mechanism other than hypervisors? Cheers, Richard (Working from home: <http://pic.twitter.com/NetsgOS2>) -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Richard Lewis ISMS, Computing Goldsmiths, University of London t: +44 (0)20 7078 5134 j: ironchicken(a)jabber.earth.li @: lewisrichard s: richardjlewis http://www.richardlewis.me.uk/ -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- [ 1656.306197] rs:main Q:Reg invoked oom-killer: gfp_mask=0x201da, order=0, oom_adj=0 [ 1656.306215] rs:main Q:Reg cpuset=/ mems_allowed=0 [ 1656.306222] Pid: 1135, comm: rs:main Q:Reg Not tainted 2.6.32-5-xen-amd64 #1 [ 1656.306230] Call Trace: [ 1656.306242] [<ffffffff810b7318>] ? oom_kill_process+0x7f/0x23f [ 1656.306251] [<ffffffff810b783c>] ? __out_of_memory+0x12a/0x141 [ 1656.306259] [<ffffffff810b7993>] ? out_of_memory+0x140/0x172 [ 1656.306268] [<ffffffff810bb742>] ? __alloc_pages_nodemask+0x4ec/0x5fe [ 1656.306278] [<ffffffff810bcca9>] ? __do_page_cache_readahead+0x9b/0x1b4 [ 1656.306286] [<ffffffff810bcdde>] ? ra_submit+0x1c/0x20 [ 1656.306294] [<ffffffff810b5a66>] ? filemap_fault+0x17d/0x2f6 [ 1656.306302] [<ffffffff810cba22>] ? __do_fault+0x54/0x3c3 [ 1656.306313] [<ffffffff8130c7d1>] ? __wait_on_bit_lock+0x76/0x84 [ 1656.306323] [<ffffffff8100c3a5>] ? __raw_callee_save_xen_pud_val+0x11/0x1e [ 1656.306333] [<ffffffff810cdda8>] ? handle_mm_fault+0x3b8/0x80f [ 1656.306342] [<ffffffff8100ecf2>] ? check_events+0x12/0x20 [ 1656.306351] [<ffffffff8130fb26>] ? do_page_fault+0x2e0/0x2fc [ 1656.306360] [<ffffffff8130d9c5>] ? page_fault+0x25/0x30 [ 1656.306366] Mem-Info: [ 1656.306370] Node 0 DMA per-cpu: [ 1656.306376] CPU 0: hi: 0, btch: 1 usd: 0 [ 1656.306381] Node 0 DMA32 per-cpu: [ 1656.306388] CPU 0: hi: 186, btch: 31 usd: 75 [ 1656.306397] active_anon:55210 inactive_anon:55287 isolated_anon:1350 [ 1656.306398] active_file:10 inactive_file:11 isolated_file:26 [ 1656.306400] unevictable:0 dirty:0 writeback:171 unstable:0 [ 1656.306401] free:1180 slab_reclaimable:922 slab_unreclaimable:2187 [ 1656.306402] mapped:16 shmem:7 pagetables:7768 bounce:0 [ 1656.306422] Node 0 DMA free:2032kB min:80kB low:100kB high:120kB active_anon:6168kB inactive_anon:6312kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:14868kB mlocked:0kB dirty:0kB writeback:8kB mapped:20kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:76kB kernel_stack:16kB pagetables:292kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:3 all_unreclaimable? yes [ 1656.306456] lowmem_reserve[]: 0 489 489 489 [ 1656.306467] Node 0 DMA32 free:2688kB min:2788kB low:3484kB high:4180kB active_anon:214672kB inactive_anon:214836kB active_file:40kB inactive_file:44kB unevictable:0kB isolated(anon):5400kB isolated(file):104kB present:500960kB mlocked:0kB dirty:0kB writeback:676kB mapped:44kB shmem:28kB slab_reclaimable:3688kB slab_unreclaimable:8672kB kernel_stack:1232kB pagetables:30780kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:328 all_unreclaimable? yes [ 1656.306501] lowmem_reserve[]: 0 0 0 0 [ 1656.306512] Node 0 DMA: 4*4kB 1*8kB 0*16kB 1*32kB 1*64kB 1*128kB 1*256kB 1*512kB 1*1024kB 0*2048kB 0*4096kB = 2040kB [ 1656.306537] Node 0 DMA32: 232*4kB 2*8kB 1*16kB 0*32kB 1*64kB 3*128kB 1*256kB 0*512kB 1*1024kB 0*2048kB 0*4096kB = 2688kB [ 1656.306561] 8628 total pagecache pages [ 1656.306566] 8586 pages in swap cache [ 1656.306571] Swap cache stats: add 1078026, delete 1069440, find 120149/196407 [ 1656.306579] Free swap = 4kB [ 1656.306583] Total swap = 1048568kB [ 1656.308293] 131072 pages RAM [ 1656.308302] 4044 pages reserved [ 1656.308307] 22558 pages shared [ 1656.308311] 123779 pages non-shared [ 1656.308317] Out of memory: kill process 489 (apache2) score 125474 or a child [ 1656.308324] Killed process 964 (apache2)

3 5

OT Maths Jam
by Steve Engledow 26 Jul '12

26 Jul '12

Hi folks, Would anyone be interested in a Norwich maths jam? See http://www.mathsjam.com/ for (fairly vague) details or check the twitter account (@MathsJam). tl;dr: We get together in a pub on the second-to-last tuesday of the month and be geeky. I know, it sounds like the pubmeet; but this time we be geeky about mathsy things! I reckon there ought to be enough maths geeks among the linux geeks for this to be relevant :) Steve

3 3

Pubmeet report
by Steve Engledow 25 Jul '12

25 Jul '12

Hi all, It's been a while since a pubmeet had a write-up but I thought it was worth a go :) On a suggestion from rlp10, last night ended up being somewhat of a PGP key-signing party. All of us around the table (there were 6 of us) - plus one passer-by that I happened to know - had PGP (or rather GPG) keys so, over the course of the night, we managed to each sign eachothers keys. There was even provision of ID and encrypted emails sent to verify identity and key ownership. A fairly textbook key-signing I'd say. Additionally, we collectively managed to get a sensible mutt config together for getting GPG integrated and working. For reference, the magical invocation to make mutt understand encrypted/signed mail from Macs and Thunderbird is: message-hook '!(~g|~G)~b"^-----BEGIN\ PGP\ (SIGNED\ )?MESSAGE"' "exec check-traditional-pgp" Stick that in your .muttrc and it all works nicely. (You need a `source /path/to/muttrc.gpg`) line in there somewhere too. The path varies by distro.) Aside from the PGP-related fun, katsmeat had brought an interesting old PC that had a built-in LCD display and ran Microsoft BASIC (I don't remember what the machine actually was) and I offloaded a load of old hardware onto rlp10 \o/ The food didn't seem as good as usual. The beer did. Until next month! Steve (Stilvoid)

6 18

SyncNorwich
by Paul Grenyer 25 Jul '12

25 Jul '12

Hi All I just wanted to make sure you guys were all aware of www.syncnorwich.com, a new group for people in Norwich interested in Technology, Startups and Agile. Out next event is some lightning talks on the 16th August and there's a Norwich lunch on the 23rd August. -- Thanks Paul Paul Grenyer e: paul.grenyer(a)gmail.com b: paulgrenyer.blogspot.com t: pjgrenyer SyncNorwich: http://www.syncnorwich.com ACCU Member: License to code: http://www.accu.org

1 0

kernel:journal commit I/O error
by Mark Rogers 19 Jul '12

19 Jul '12

I have an ARM box which was working fine until it went to site. It's running Debian and I only have access to it via SSH (although at the moment I have someone on site who can force it to reboot). Twice today I've received the error "kernel:journal commit I/O error" to my SSH terminal, after which point the root filesystem gets unmounted and I can't do anything even though the unit is still "up". Eg: $ ls -bash: /bin/ls: No such file or directory Any ideas what would be causing this? It's an expensive SD card in these units (not a cheap no-brand) This is the unit in case anyone is interested, it's running Debian 6: http://www.newit.co.uk/shop/proddetail.php?prod=DreamPlug_N I'd also be interested to know if there's anything I can do down an SSH connection to force it to reboot, given the lack of access to the filesystem to even run "sudo" never mind "reboot". I'm guessing that sending Alt-Ctrl-Del or Alt-SysRq-B via SSH are out... -- Mark Rogers // More Solutions Ltd (Peterborough Office) // 0844 251 1450 Registered in England (0456 0902) 21 Drakes Mews, Milton Keynes, MK8 0ER

4 15

linux apparel
by Peter Alcibiades 18 Jul '12

18 Jul '12

Hi everyone, I have three huge, I mean xxxl, linux apparel t-shirts looking for a good home. One looks like its been worn a couple of times since the brilliance of the yellow has faded slightly, the other two I don't think have been. Does anyone want them? They are fairly brilliant yellow, with a large black and white plastic penguin on the front, and on the back there is a black and white legend to the effect that this garment requires appreciation of open source freedom. Several years old. Maybe 10? Should have brought them to last Thusday, but I have not come to those for some time now. I can mail them if you let me have an address. Otherwise, its going to be the charity shop. Peter

1 0

torcl
by richard.lee.parsons＠gmail.com 14 Jul '12

14 Jul '12

Hi all After some conversations with some Aluggers, I've thrown together a bash script for downloading torrents from the commandline. It searches isohunt, downloads your selected torrent file and kicks off the torrent client all from the warmth and safety of your favourite terminal. Perhaps it may be useful to some others on the list. https://github.com/rlp10/torcl It's pretty ugly scripting, so please forgive that. :) Richard

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