Search Results: "tar"

27 June 2007

loldebian - Can I has a RC bug?: Im droin u a 7 of harts

Im droin u a 7 of harts for u to has a nice day Im droin u a 7 of harts for u to has a nice day. Joey using his brand-new notebook. Photo by Christian Perrier.

Martin F. Krafft: Contact forms and idiot corporations

Every now and then I must get in touch with a company whose client I am. With that I mean that the company has my record in their customer database and that I can log in to their webpages with the associated account. Since companies generally don't consider their clients' comfort, they'll usually make you click about a dozen times through mazes of silly questions until you reach a HTML form you can use to send your message on the way. If you take a wrong turn anywhere in the maze, you'll be dropped into a list of frequently asked questions and have to start from scratch your quest for the contact form. I understand the motivation, which is to shield the understaffed customer support department from just those frequently asked questions. However, never has my issue been adequatly answered in those shielding documents. For instance, with Lufthansa, I've had to request ticket changes because they had screwed up (and not my travel agent), or request replacement member cards. And in the Case of Cablecom, I've been trying for months to hear their statement on why my 3500/350 kbps cable connection only ever delivers around 1500/250 (as established in a long-term trial over almost seven weeks), and to get them to stop sending several pages of advertisements about the same products with each and every invoice I get. In none of these cases could I find any useful information online, so I had to embark on the painful journey to the contact form, formulate my request into a tiny text box that would often not even be able to show start and end of a single sentence without scrolling (this is German after all), nor respect line breaks, and then hit the "send" key with a drop of sweat on my forehead because you never know what kind of crack the CGI on the other hand had smoked just a minute ago. What pisses me off most of all is, however, that in the two cases of Lufthansa and Cablecom (this list is not exhaustive, I'm sure, Sunrise is another offender), you have to login to your customer account in order to be able to fill out the contact form, where they ask you for all your contact details again. I don't understand why they want gender, birthdate, postal address, phone number, email address and whatever else for a simple support request one means of contact so they can get their answer to you should be enough. But what I surely don't understand is why they can't just use your login cookie to retrieve all those data from their data store. It sure seems like they're not really in control of their own infrastructure. And this list is not exhaustive. NP: Dredg: Live at the Fillmore

Martin F. Krafft: Dog control theory

For the next two weeks, I am proud owner of a dog. Or well, at least care taker:
Zeno and myself
Zeno, that's his name, is absolutely convinced that he is the centre of the universe, the "l'ombelico del mundo", as Jovanotti would sing. So it's very incomprehensible to him if I do anything but play with him and he follows me even to the toilet to make sure I don't miss a chance. Apart from having learnt to type single-handedly now (the other hand petting him), what's really amusing is his never-ending, asymptotic quest for perfect comfort. Enter the sequence at any point:
  1. if not being petted, walk up to martin
  2. strike paw against whatever body part is available.
  3. if martin does not react, bite into his thigh, lightly.
  4. repeat 1-3 until martin reacts and starts petting.
  5. slowly start to lie down, thereby leaving martin's circle of reach
  6. wait a second so as to not arouse suspicion
  7. stand up, continue at 1.
I find this extremely reminiscent of control theory or a crap PID controller. You'd think dogs are intelligent until you witness the 20th iteration. I am not exaggerating. And I still love that dog. NP: Gazpacho: When Earth Lets Go

Michal Čihař: Gammu and Symbian 3rd generation

As I recently got yet another round of requests to make Gammu work with 3rd generation of Symbian phones. I know there is still more and more of them, but none of developers have possibility to port gnapplet to work with these phones. Basically all required steps are described on Nokia website, so it should not be that hard. It only needs somebody who is able to write in C++. You can get CDK for Symbian phones for free (eg. from Nokia, but I guess that from any phone vendor) and start to port gnapplet. Any contributions in this area are welcome, because I can't do much without Symbian phone.

Russell Coker: Strange SATA Disk Performance

Below is a GNUPlot graph of ZCAV output from a 250G SATA disk. The disk has something wrong with it (other disks of the same brand in machines of the same configuration give more regular graphs). The expected graph will start high on the Y scale (MB/s) and steadily drop as the reads go to shorter tracks near the spindle. The ZCAV results page has some examples of the expected results. If you have any ideas as to what might cause this performance result then please make a comment on this blog post. strange-sata

Evan Prodromou: 7 Messidor CCXV

Someone in the #mediawiki channel the other day asked, "Would it be possible to have easy-to-parse error messages?" and I thought, "Wow, that sounds like a microformat in the making." Probably one of the most common HTML patterns in Web applications is error messages. We see them all the time on the Web: login errors, form validation errors, backend errors and user input errors. But what if this common pattern was standardized? If HTML error messages all followed a similar format, we could have browser plugins that recorded and analyzed the errors that come up. They could either feed back this structured error data when we needed it -- say, when filing a bug report -- or use the error data to help us find workarounds or documentation online. I brought the idea up in the #microformats channel on Freenode, and it got a good response, so I took the next step and created a list of error message examples and some error message brainstorming on the microformats wiki. Hopefully this can be the start of some interesting feedback loops in software errors. tags:

26 June 2007

Ross Burton: Tasks 0.9

After fixing a few bugs, cleaning up the source code, and even adding a few new features, Tasks 0.9 is ready. Most of the changes were internal, but there are a few user-visible changes.

Russell Coker: Advertising Free Software Projects

Today I just noticed the following advert on one of my web pages:
MINIX3 is a new reliable
free operating system. Smaller
than Linux. Try it It’s free!
www.minix3.org This made me think about some of the potential ways of advertising free software projects. It seems that in some ways Google Adwords is not the only way that can be used for advertising free software, and in some ways isn’t the most effective. I believe that the most effective method would be to ask people to advertise the project. I am generally positive towards the aims of the Minix project and am happy to give them some free advertising if asked (I’ve just given them a free advert above without being asked). While Google adlinks and equivalent things in blog posts are easy to set up, effective advertising may require something more. A series of pictures (in different sizes and color schemes) for the link would help, and the project would ideally have a specific landing site for people who see the advert. Someone who sees an advert targeted to newbies will have different requirements from the web site to someone who already knows about it and typed the URL in from memory! For a big campaign you would probably want to have multiple landing sites for different adverts targetted at different people. One example of how this can be used is my Bonnie++ page which gets about 6000 hits a month - many of which are from users of proprietary Unix. Linux users often have Bonnie++ as part of their distribution and don’t have much of a need to visit my web site so I expect that even though the vast majority of Bonnie++ users run Linux the proportion of site visitors might not be so strongly in favour of Linux. I would be happy to place an advert on that page to encourage proprietary Unix users to use the most free distribution of Linux if someone was to prepare the advert and give me some HTML code I can easily add to my site. To some extent the web site for every free software project could be used to advertise some related projects (or projects that are liked by the people who run the site). If you are a contributor to a free software project that you think I would like then feel free to prepare an advert and send it to me. If it fits with what I’m doing then I’ll give you some free advertising! Blogs are also a good mechanism for advertising free software projects, but it seems that this is already being used a lot - having said that… As a gratuitous plug: my favourite distribution of Linux is Debian (here are my Debian blog entries) and I run NSA Security Enhanced Linux (SE Linux) on all my machines (here are my SE Linux blog entries).

Jonathan McDowell: Nice guy EDI

I've spent the last week and a bit in Edinburgh, at DebConf7. I found it took me a couple of days to adjust for some reason, but after I'd managed to lose all sense of time everything went much better. I'll probably spend the next week recovering and catching up with real life. I have to say I don't feel I achieved a whole lot while I was there. When I went to my first DebConf (DebConf4, in Brazil) I spent a lot of time hacking and making progress on things. I didn't manage to do so well in Finland, nor this year. I'm not sure that's entirely what DebConf is about though. I saw a lot of people; the UK crowd who turn up to most things, people I hadn't seen since Finland, and those who I hadn't see since Brazil (and must try harder to see more often). And of course several names I was able to put to faces. This is a really useful part of such events - I find it's much easier to deal with people online once I've met them in real life and have an idea where they're coming from. Having said I didn't achieve much I did many to leave with a lot of things in my personal todo list. I had the calendar conversation a couple of times again, at greater length, resulting in being told that I should just do it. So I need to think about a proper design. I started looking at Just Writing Code, but the problem is such that I believe a more rigorous approach is required. Another item was ARM hacking; I sat in on the ARM BOF and caught the end of the Emdebian stuff, as well as talking to Wookey and Neil Williams quite a bit about it. Wookey's convinced me that working on mainline Balloon2 support is still useful, even if everyone is more interested in Balloon3. And I thought a bit about starting to do some AM work again, assuming I can find enough time to do a decent job of it. Mao was sadly lacking; I got a couple of games in, but not the number I'd come to expect from previous DebConfs. I think the trick is to find Marga sooner... In addition to the travel to Edinburgh we ended up with a daytrip to the Isle of Bute - thanks to Patty Langasek for organising this. We managed not to lose anyone, and had a visit to a public loo from 1898. Post DebConf a bunch of us ended up in Solva for a party to celebrate Daniel and Rob's civil partnership. It was well worth the travelling, and good to see people who hadn't been at DebConf. Finally, on the way back home, we detoured via Stonehenge. Anyway. Now I'm back home, Katherine's turned up for a bit and hopefully I'll manage to do some of my todo list. See y'all next year in Argentina, assuming I can find the funds.

Ian Haken: A vlosuts update

I'd say vlosuts is just about alpha at this point. It perfectly manages building an image and then upgrading (at least on the systems I've tested it on) and I haven't seen any major bugs. The main feature I'd like to get working is support for a Xen backend. This shouldn't be too difficult, it's just taking me a bit of effort to get Xen working. It would've been easy enough, but I just couldn't get the network configured. I followed guide after guide, and finally figured out the problem was that my wireless card didn't support bridging. Which explains why I'd never managed to get that to work in the past either. So now I'm reconfiguring my Xen setup with NAT, which should give me a system good enough for testing. After that I'll start fixing some of the less important bugs and adding some features here and there.

Evan Prodromou: 6 Messidor CCXV

We had a great weekend this last weekend here in Montreal. Yesterday, June 24, was Saint-Jean-Baptiste Day here in Quebec -- the national holiday of this cool and fun nation. St. Jean Baptiste is important to me in a lot of ways. Of course, it's cool that it's the national holiday of our adopted new home. But John the Baptist, the patron saint of Quebec, is also our family's name saint. ''Prodromos'' means "forerunner" in Greek, and it's one of the titles of St. John. Most of all, it's the day that Maj and I moved to Montreal. We came in on St. Jean Baptiste Day, 2003, and we've been here ever since. We drove my beautiful 1972 Citro n DS from San Francisco, where my niece Elena had just been born, all the way out here. We arrives on June 24th and wandered around the McGill Ghetto looking for our sight-unseen sublet. It's hard to believe it's only been 4 years -- it seems like so much longer. We had a good day yesterday. The three of us went to Piknic in the afternoon and hung out with our friends Jeremy and Lina and their two great kids Clea and Sylvie. We had a lot of hummus and pasta salad and bread and cheese and generally had a great time. Meg and Catherine came and hung out for a while, and also our friend Kristen, who's 7 months pregnant and has a 10-month-old. Good luck on that one. Most of all a pretty day enjoying the outdoors in our new home town, as well as fun dancing to house under a big Calder statue. How great is that? tags:

72 hours from Flickr I forgot to mention that we had a really nice time on Friday evening going to the 24 Hours of Flickr party at the SAT. Heather Champ, community leader at Flickr and welcomer to partiers, put it well: "We have three requirements for Flickr parties: the food must be good, the drinks must be copious, and the schwag must be ample." And that's exactly what happened. All the usual Montreal suspects were out in force: YULblog types, Web entrepreneurs, Web pranksters. It was great seeing m-c and c-c, who wore their awesome Flickr Socks -- although they each had a matching pair. I also talked to Allen Morris, which was really fun. He's a developer living now in Saranac Lake, one of the towns in the Adirondacks I find strangely compelling. We exchanged GPG key signatures and talked a lot about the Bay Area (California), where we both once lived. Probably my best talk was with Heather Champ and Derek Powazek. We talked about their joys of creation of JPG Magazine, the despair of leaving it, and looking forward to the future. We also chatted a lot about print on demand technologies, which we're evaluating for Wikitravel. Heather took the photo of my friend Ben Cerveny at Burning Man that's become his avatar icon on about every social software platform I know of. It must be good to capture someone in the way they want to think of themselves. I took my own self-concept picture by putting the camera on the dashboard of my Citroen. Heh. All in all a good party. One thing I was interested to find out was that there's a Yahoo! Quebec, which launched last month and I guess just slipped by me. Sadly, if you click on the "English" button, it takes you to... Yahoo! Canada. Hey, Yahoo! There are actually a lot of anglophones here! Just in case you were wondering. tags:

Montreal Web Development Book Club Montreal Web scene stalwart Heri Rakotomalala -- the man with the magic name, originally from Madagascar, along with Montevideo and Marfa, one of the M-places on my travel wishlist -- recently started a Montreal Web Development Book Club. It's a meeting for people interested in the practical side of the Web to talk about the books they read and let that drift into talk about the work we do and ideas we have. I think the book club is an awesome idea. Book clubs are a great grass-roots intellectual meetup that we don't often celebrate in the post-flash mob BarCamp-ized world. The great thing about a book club, for Web people, is that it filters out the bullshitters and dilettantes. If you're going to a book club, you're going to have to know what you're talking about, and you're going to have to care about the subject. The book gives focus that keeps the conversation from drifting to tangential topics. Flakes and hangers-on just don't have the stamina for it. Also, we met at La ka, so it was nice to have some beers in a good place on a hot night. Why not? We managed to talk about a lot of good books, too. Jean-Fran ois <something> (I didn't get his last name) talked about In Search of Stupidity, a look at the last 25 years of marketing and business blunders in the high-tech realm. Our industry is subject to a lot of decisions that seem absolutely self-defeating in hindsight, and the book goes in-depth on 15 case studies -- like Wordstar, Ashton-Tate and Borland. It sounds like a great cautionary tale for Web 2.0 startup mavens. Heri talked about the book Information Architecture for the World Wide Web -- the infamous "Polar Bear Book". It sounds like a really good book for doing initial planning for a Web site, but I'm really interested in tools for profiling an IA effort. We get about 2 million unique visitors a month at Wikitravel, for example, which is a huge amount of usability data I could be mining. But I don't really have the tools for it, so I don't do it much. I'd love to know, for example, about people who land on a Wikitravel page from a search engine and then leave. What were they looking for? Why couldn't they find it? Also, users who browse through our pages clicking on links, then resort to a full-text search. What did they think they were clicking on, and what were they looking for instead? Did they find it? How can we put that in front of them in the first place? Most of all, I want to know how and why people start editing Wikitravel pages, and why they stop. Of people who click the "edit" button, only 1 in 17 click "save". (That is one bit of clickpath analysis I've done.) Why? I've often been tempted to put a survey up when someone navigates away from our edit page. "Why didn't you save? Tell us so we can fix it for other people." I talked about the book I just finished reading a few weeks ago, Everything is Miscellaneous. It's the latest book by Dave Weinberger about how we impose order on information to make it easy to understand and retrieve. It's an awesome book -- really fun -- especially for someone married to a knowledge management expert. I don't think I gave a good enough description of the book to ignite the club's interest, but I hope they check it out, because it's really readable and good. At the end of the meeting Heri took a poll and decided that we'll continue doing the book club on the last Monday of the month. I've already picked out my book for next month: RESTful Web Services. I've heard good things about this book (admittedly mostly from the co-author Leonard Richardson) and I want to give it a look-see. So book-club fodder it is. ''Update: Heri has his own book club report here.'' tags:

25 June 2007

Wouter Verhelst: Joshua Bell in the metro

A few months ago, the Washington Post featured an article about Joshua Bell playing his violin (which happens to be a Stradivarius) in a Washington metro station. Contrary to their expectations, nobody stopped by to listen. The article tries to find reasons for why this happened, digging into theories by a number of famous philosophers. While those are undoubtedly not far from the truth, let me dig up another theory: Joshua Bell may be one of the best musicians in the world; that doesn't mean he's one of the best street musicians in the world. You see, if you play your Stradivarius in a concert hall, you don't have to do much to get people's attention. If your name is Joshua Bell and you play in the New York Opera House, people pay good money to get a seat months in advance, they circle the date on their calendar, and they look forward to it for weeks. When the big day arrives, they dress up, they drive up to the opera house, they queue for the privilege of being allowed to show their tickets and being allowed in, they take their seats, and they wait in excitement and anticipation until the big moment arrives. If your name is Joshua Bell and you play your Stradivarius in a concert hall, people will clap their hands you before you've even started. You'd better make it be good, or they'll demand their money back. If, however, you play on the street, then that's a completely different matter. You don't get to have people circle the date of your street concert months in advance. You have exactly one second to let them know you're playing. You don't get to have an audience that will clap their hands the very moment they see you turn the corner; instead, you'll see an audience that would rather you did not stand in the middle of the way like that, so that they would not have to look out for you. In short, you don't get their attention on a silver platter; instead, you have to earn it. As someone who's done street music in the past, I can tell you that earning someone's attention isn't something you will do by playing the most difficult music that can be found. You should remember that you've got just a few seconds to catch someone's attention; from the moment they vaguely hear someone's playing, until that time when they're getting annoyed at the volume your, no doubt wonderful, instrument is making. If you want people to stop and listen, you need to do it in that very short timeframe. A wild and fast virtuoso piece, while sure to get you a great reaction by an audience in an opera house, is only a very noisy thing if you just get a few seconds of it—even if those few seconds are by the best violin player alive. The best way to get someone's attention is to give them something they recognize. The article notes the reactions from a few passers-by. It did not surprise me that of the three or four people who actually stopped and listened, one recognized the violinist as Joshua Bell, and the other had been a violinist himself in a previous life. Both had something they recognized, which made both stop for a few moments to check what they were seeing. That's what gave them more time to appreciate how truly beatifull this music was, and that's why they waited. The real way to get people to stop, to get a crowd around you, and to have them to listen to you, is not to play what gets you the best results in an Opera House or other concert hall. Instead, you should play something that will catch people's attention. A brilliant piece that is unknown will not do that. A funny variation on "Oh When The Saints" will, because people recognize the music. That's not to say that street musicians should only play stuff like "Oh When The Saints". Getting money from playing on the street has more to it than just the music you're playing; just as important is the place where you're playing, and the time when you're doing it: A good street musician knows these things, and applies them even without knowing. He'll instinctively know whether it's a good day to do street music, and he'll rather go to a bar and have a hot drink if it's not. So why didn't Joshua Bell get a crowd around him? Easy: he isn't a very good street musician.

Gunnar Wolf: Back from DebConf7

Ok, I'm officially back. Yup, when you have a meeting just over your regular lunch time and are suddenly seen as the guy who will fix the institute's video needs just because you worked manning cameras with the amazing DC7 video team, it just means you are back home. Lets see how several projects that have sprang up in the last couple of weeks (both at DebConf and at work) start materializing.
Anyway... DebConf was great. Just great. This time I had time both to feel I was useful and productive (mainly doing video-related stuff, although on some other points as well), to attend several interesting talks (although manning the camera did not leave my attention as complete as I would have liked), to have several nice chats, to play a good couple of hands of Mao - Hell, thanks to Kitty, I managed even to have some chats _while_ having a hand of Mao!
Of course, I was not productive neither with my Real Life duties nor with with the Debian stuff I wanted to hack on - In fact, the most productive period during the two and a half weeks I was away (excluding probably the two days I spent understanding/hacking Pentabarf with Dami n) was the flight back - During the ~12hr we were on the air, I managed to read the second half of my book, to review two chapters for a thesis, to write a (really simple) article and to work on another one.
Anyway... Thanks to everybody. I had a great time, and am only looking forward towards Argentina.
Ah, and I also got The Debconf Flu.

MJ Ray: Stupidity: Reader Comment: Verified by VISA

Stephen Touset commented:
"The worst offender in my experience is the "Verified by VISA" program. They restrict you to a subset of characters (alphanumeric, if I recall correctly) and even restrict the maximum length! You know what the worst part of it is, though? If they were using a widely-published, widely-analyzed, and widely-reviewed secure hash standard like SHA-1, Whirlpool, or any number of alternatives, these restrictions wouldn't be in place. This tells me that they're likely not using a well-reviewed standard, and instead have probably come up with their own bastardized password "encryption"."
I'm a bit worried by this, but I'm moving my customers to Verfied by VISA and Mastercard 3DSecure because of the carrot-and-stick used by the payment gateways. Am I sleepwalking off the cliff here?

MJ Ray: Blogging from debconf7: 4. Sleepin ur BoF, hijakin ur sesh, climbin ur volkano

This has been delayed for a few days, for reasons I explain in another post, so my remaining debconf posts will be published quite quickly, every few hours. Monday started with me nearly asleep in the back of the Debian-Med session. Interesting stuff and I'm starting to get involved in supplying web apps to the health sector, but I must watch the session back. Then bureado's excellent debian in venezuela talk and a big shock for me when I got called out. The afternoon and evening were mentioned in the last post. Tuesday opened with me confused in the Xen session and then I went to a good-looking session on combining the debian-installer, ubuntu OEM bits, backuppc and openvpn but lkcl didn't show. (His diary suggests he was around. Wonder what happened.) I kicked the session along a bit and learned stuff from others about preseeding, FAI, backuppc, bacula, amanda and so on, but it didn't seem like anyone had plugged these together in quite the same way. At the end of the session, I bumped into Eddie Bleasdale who it seems is working with Phil Hands and lkcl on a very interesting project. He spoke more about it in a meeting the afternoon, hoping that Phil would arrive to handle the technical side. Phil timed his entry to perfection, about 30 minutes after the end of the talk. In between the hijacked talks, I went for a walk up to the top of Arthur's Seat and back with jumpula and someone else whose name I've forgotten - sorry! Oh, and what is it with all the loldebian posts this week?

Mario Iseli: Swisscom sucks

First of all an introduction for the readers outside of Switzerland: Swisscom is a monopolistic organization which has the right to install DSL infrastructure in Switzerland and sells those line to the Wholesale-Customers (aka the “normal” providers).
Some weeks ago Swisscom increased the bandwidth for the business customers (aka myself for example) and since then my connection failed at least once per day. The only solution to fix that was resetting the whole ADSL modem which fits as a bridge to PPPoE and then restart the pppd after all. Since I’m not often at home but use the machines from remote over ssh to read mail, irc, debug dns stuff, test software on one of the public sid machines. So, my systems are totally unreliable.
I wrote a mail to my provider some weeks ago, didn’t really get e good feedback. When I called them by phone I was told that Swisscom reduced my bandwidth again and this should resolve the problem. Dear Swisscom, it still does _NOT_ work and I have several disconnects per day. I wanted to use my machines when I was at Debconf7 last week in Scotland, but at the time when I arrived at Teviot my line was down and I had to read my mail during this time via IMAP from the 2nd MX. :(
I also have the feeling that my provider doesn’t want to help me, nobody gave me instructions on how I could debug this better, they just gave me a formular to open a troubleticket itself and there I would need to subscribe that all costs have to be payed by myself what I can’t as a student. :( Ok, so I have a total unstable Internet connection and as it looks like I have to switch from ADSL to Cable internet in a few months, even if that also has big disadvantages. :(

Adeodato Sim : Debconf7 report

So Debconf7 has come to an end, and I’m pretty sure this has been my best Debconf so far. Although I did not manage to attend many talks and discussions, and did not socialize as much as I would’ve wanted with the people I did not already know (does Mao count as socializing?), I’ve on the other hand felt good throughout all its duration, which is great. On the productivity side, I think I’ve done okay. Strangely enough it’s not been Debian the main target of my hack hours, God only knows why. Instead, I made a couple of contributions to Bazaar, one of the new generation distributed version control systems. But I’m sure my Debian work will gain momentum in the near future, so no worries. Finally, I must say I’m in debt with a bunch of people who thought it was worth having me attend, and brought me here when it seemed it was too late. I’m very grateful for that, really. As always, thanks to the orga team for their terrific work, and hope to make it to Argentina next year. Update 1: Forgot to say, I went to the Genderfuck party in The Forest. It was pretty cool, and a first. Update 2: Brittish Airways lost my luggage (and I seem not to be alone in this). P.S.: I think I’ve got the Debconf flu. \o/

24 June 2007

Miguel Gea: OOXML

Steve Kemp: Unknown, even to its own employees, its massive profits are generated by military technology, genetic experimentation and viral weaponry

The scanning of the Debian source archive for security bugs has begun. I've wrote about this previously and there was some interest in how it worked, so I've put up a simple webpage describing the process. There are a lot of results to go through, but so far I've managed to find one local root exploit and many many many trivial problems. Sample bugs: Unfortunately my usertags seem to be broken. This was working a day or two ago. Not sure if I fucked up or if the BTS is broken ..?

Russell Coker: Xen and Heartbeat

Xen (a system for running multiple virtual Linux machines) and has some obvious benefits for testing Heartbeat (the clustering system) - the cheapest new machine that is on sale in Australia can be used to simulate a four node cluster. I’m not sure whether there is any production use for a cluster running under Xen (I look forward to seeing some comments or other blog posts about this). Most cluster operations run on a Xen virtual machine in the same way as they would under physically separate machines, and Xen even supports simulating a SAN or fiber-channel shared storage device if you use the syntax phy:/dev/VG/LV,hdd,w! in the Xen disk configuration line (the exclamation mark means that the volume is writable even if someone else is writing to it). The one missing feature is the ability to STONITH a failed node. This is quite critical as the design of Heartbeat is that a service on a node which is not communicating will not be started on another node until the failed node comes up after a reboot or the STONITH sub-system states that it has rebooted it or turned it off. This means that the failure of a node implies the permanent failure of all services on it until/unless the node can be STONITH’d. To solve this problem I have written a quick Xen STONITH module. The first issue is how to communicate between the DomU’s (Xen virtual machines) and the Dom0 (the physical host). It seemed that the best way to do this is to ssh to special accounts on the Dom0 and then use sudo to run a script that calls the Xen xm utility to actually restart the node. That way the Xen virtual machine gets limited access to the Dom0, and the shell script could even be written to allow each VM to only manage a sub-set of the VMs on the host (so you could have multiple virtual clusters on the one physical host and prevent them from messing with each other through accident or malice). xen ALL=NOPASSWD:/usr/local/sbin/xen-stonith Above is the relevant section from my /etc/sudoers file. It allows user xen to execute the script /usr/local/sbin/xen-stonith as root to do the work. One thing to note is that from each of the DomU’s you must be able to ssh from root on the node to the specified account for the Xen STONITH service without using a password and without any unreasonable delay (IE put UseDNS no in /etc/ssh/sshd_config. The below section (which isn’t in the feed) there are complete scripts for configuring this. (more…)

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