Archives

Categories

New Portslave release after 5 Years

I’ve just uploaded Portslave version 2010.03.30 to Debian, it replaces version 2005.04.03.1. I considered waiting a few days to make the anniversary but I wanted to get the bugs fixed.

I had a bug report suggesting that Portslave should be removed from Debian because of being 5 years without a major release. It has been running well 24*7 on one of my servers for the last 5 years and hasn’t really needed a change. There were enough bugs to keep me busy for a few hours fixing things though.

The irony is that I started using dates as version numbers back when there were several forks of Portslave with different version numbering schemes. I wanted to show that my fork had the newer version and a recent date stamp was a good indication of that. But then when Portslave didn’t need an update for a while the version number showed it and people got the wrong idea.

The new project home page for Portslave is on my document blog [1].

Server Costs vs Virtual Server Costs

The Claim

I have seen it claimed that renting a virtual server can be cheaper than paying for electricity on a server you own. So I’m going to analyse this with electricity costs from Melbourne, Australia and the costs of running virtual servers in the US and Europe as these are the options available to me.

The Costs

According to my last bill I’m paying 18.25 cents per kWh – that’s a domestic rate for electricity use and businesses pay different rates. For this post I’m interested in SOHO and hobbyist use so business rates aren’t relevant. I’ll assume that a year has 365.25 days as I really doubt that people will change their server arrangements to save some money on a leap year. A device that draws 1W of power if left on for 365.25 days will take 365.25*24/1000 = 8.766kWh which will cost 8.766*0.1825 = $1.5997950. I’ll round that off to $1.60 per Watt-year.

I’ve documented the power use of some systems that I own [1]. I’ll use the idle power use because most small servers spend so much time idling that the time that they spend doing something useful doesn’t affect the average power use. I think it’s safe to assume that someone who really wants to save money on a small server isn’t going to buy a new system so I’ll look at the older and cheaper systems. The lowest power use there is a Cobalt Qube, a 450MHz AMD K6 is really small, but at 20W when idling means a cost of only $32 per annum. My Thinkpad T41p is a powerful little system, a 1.7GHz Pentium-M with 1.5G of RAM, a 100G IDE disk and a Gig-E port should be quite useful as a server – which now that the screen is broken is a good use for it. That Thinkpad drew 23W at idle with the screen on last time I tested it which means an annual cost of $36.80 – or something a little less if I leave the screen turned off. A 1.8GHz Celeron with 3 IDE disks drew 58W when idling (but with the disks still spinning), let’s assume for the sake of discussion that a well configured system of that era would take 60W on average and cost $96 per annum.

So my cost for electricity would vary from as little as $36.80 to as much as $96 per year depending on the specs of the system I choose. That’s not considering the possibility of doing something crazy like ripping the IDE disk out of an old Thinkpad and using some spare USB flash devices for storage – I’ve been given enough USB flash devices to run a RAID array if I was really enthusiastic.

For virtual server hosting the cheapest I could find was Xen Europe charges E5 for a virtual server with 128M of RAM, 10G of storage and 1TB of data transfer [2], that is $AU7.38. The next best was Quantact who charges $US15 for a virtual server with 256M of RAM [3], that is $AU16.41.

Really for my own use if I was paying I might choose Linode [4] or Slicehost [5], they both charge $US20 ($AU21.89) for their cheapest virtual server which has 360M or 256M of RAM respectively. I’ve done a lot of things with Linode and Slicehost and had some good experiences, Xen Europe got some good reviews last time I checked but I haven’t used them.

The Conclusion

When comparing a Xen Europe virtual server at $88.56 per annum it might be slightly cheaper than running my old Celeron system – but would be more expensive than buying electricity for my old Thinkpad. If I needed more than 128M of RAM (which seems likely) then the next cheapest option is a 256M XenEurope server for $14.76 per month which is $177.12 per annum which makes my old computers look very appealing. If I needed more than a Gig of RAM then my old Thinkpad would be a clear winner, also if I needed good disk IO capacity (something that always seems poor in virtual servers) then a local server would win.

Virtual servers win when serious data transfer is needed. Even if you aren’t based in a country like Australia where data transfer quotas are small (see my previous post about why Internet access in Australia sucks [6]) you will probably find that any home Internet connection you can reasonably afford doesn’t allow the fast transfer of large quantities of data that you would desire from a server.

So I conclude that apart from strange and unusual corner cases it is cheaper in terms of ongoing expenses to run a small server in your own home than to rent a virtual server.

If you have to purchase a system to run as a server (let’s say $200 for something cheap) and assume hardware depreciation expenses (maybe another $200 every two years) then you might be able to save money. But this also seems like a corner case as the vast majority of people who have the skills to run such servers also have plenty of old hardware, they replace their main desktop systems periodically and often receive gifts of old hardware.

One final fact that is worth considering is that if your time has a monetary value and if you aren’t going to learn anything useful by running your own local server then using a managed virtual server such as those provided by Linode (who have a really good management console) then you will probably save enough time to make it worth the expense.

Autism vs Asperger Syndrome

Diagnostic Changes for Autism Spectrum Disorders

Currently Asperger Syndrome (AS) is one of a group of conditions that are grouped into the category Autism Spectrum Disorders (ASD).

The American Psychiatric Association plans to merge “Asperger’s Disorder” into “Autism Spectrum Disorder” [1] in version 5 of their Diagnostic and Statistical Manual (DSM). Apparently a primary reason for the change is the difficulty in assessing people into the various categories (AS, Autism, and PDD-NOS) and some variation in diagnosis between regions.

Professor Simon Baron-Cohen (a leading researcher on Autism and Asperger Syndrome) wrote an insightful article about this for the New York Times [2]. He suggests that while genetic research about the causes of Autism Spectrum Disorders (ASDs) is in progress there should be no change. If it turns out that AS and Autism have the same genetic cause then that would be good evidence to combine them into a single diagnostic category. If however they turn out to have different genetic causes then they would need different categories and he suggests that changes should be delayed until this issue is resolved. Simon also raises the issue of the status of people who have already been diagnosed, this is one of the social issues relating to a change in diagnostic criteria.

Social Issues related to Diagnosis

Unlike some disorders listed in the DSM, many (possibly most) people with AS really care about such things. I think that a common reaction to being diagnosed with Aspergers is to make the study of ASDs a “Special Interest“, which therefore makes it impossible to ignore what the psychologists are doing in this regard.

The biggest problem with changing the diagnostic criteria in this regard is that AS has a good reputation. Some people even think that it’s generally a good thing and seem to imagine that every child who is diagnosed with it will end up working for Google! This means that parents will be less likely to reject a diagnosis and therefore will be more likely to try and create a good environment for their child and seek appropriate therapies (such as social skills training and occupational therapy). I expect that a child who is diagnosed as Autistic but who doesn’t obviously conform to the worst stereotypes will likely have their parents reject the diagnosis which will lead to a bad result for everyone concerned.

The contrary view in this issue is that people who are on the spectrum but who insist that they aren’t Autistic are prejudiced and they should embrace the Autism Spectrum label as a measure of solidarity [3], while that’s a reasonable point it’s not going to happen in the short term.

Also there is the issue of adult diagnosis of AS, there are lots of adults who could benefit from being diagnosed and obstacles to such diagnosis (such as associating it with a label that is not well accepted such as Autism) are not going to do any good for anyone.

Is Asperger Syndrome really that similar to Autism?

Roy Richard Grinker (Professor of Anthropology) wrote a positive article for the New York Times about the diagnostic changes [4]. He seems to think that because in some cases it is difficult to distinguish the difference between Autism and AS they should be in a single diagnostic criteria. Based on that logic you could say that no-one should be diagnosed with an ASD because there is never a clear dividing line between the Neuro-Typical and those who are on the spectrum! Some people are clearly on the spectrum, some clearly aren’t, and some are near the border.

Roy cites his daughter and Temple Grandin as examples of Autistic people who have greater ability to relate to animals than someone who is Neuro-Typical (NT). I don’t have any particular skills in terms of relating to animals. Animals have smaller brains than humans and have thoughts that are less complex and more related to short-term issues, this makes them easier to predict in some situations. I do have significantly better skills in figuring out how to operate machines than most NTs, and this doesn’t appear to be uncommon among Aspies. I’ve read some of the material that Temple Grandin has written and watched the video of her TED talk, and I get a strong impression that she isn’t like me. Even the Aspies who are the least successful in terms of their career (IE quite unlike Temple Grandin) often seem to be like me, I can understand the way they think and recognise that the problems they face are similar to mine but merely more severe.

It seems to me that there are significant personality differences between people who have an affinity for animals and those who have an affinity for machines, maths, and engineering.

I wouldn’t be surprised if it was discovered that Autism and AS had different genetic causes, and this might mean that someone could have both sets of genes. It is obvious that the dividing line between Autism and AS is not that clear. It also seems that part of the diagnosis as implemented by psychologists may be based on the ability to act like an NT and succeed by objective criteria – IE earn a good salary in the case of adults. One thing that Roy does get right is that he notes that among people diagnosed with AS and Autism there are both “high” and “low” functioning individuals.

One thing that Roy gets wrong is the implication that Autistic people can become Aspies. An adult who is assessed without background information on their childhood may get a different diagnosis. If someone was reassessed as an adult with the full facts about their childhood available then (barring DSM changes) the same diagnosis should be returned.

Conclusion

It appears that this DSM change is going through regardless of the opinion of the people who are affected. While there is a logical basis for giving more weight to researchers than to the research subjects (who are bound to be more biased) it seems that there are some things you can’t properly understand unless you live them. When a good portion of the research subjects feel compelled to share their experiences with anyone who will listen it is disappointing that so few of the researchers appear to be listening.

How to Choose a Free Software Mission

Jane McGoningal gave an interesting TED talk about how Online Gaming can Make a Better World [1]. One of her points is that there is no unemployment in games such as World of Warcraft, there is always a “world saving” mission available to you which is just within reach of your skill level – and no-one is assigned a mission that they can’t possibly do. It seems to me that the free software development community has a similar issue, there are always “missions” available at all skill levels. Our challenge is to find ways to encourage people to accept the missions and to provide them appropriate levels of support to encourage them on their path to an “epic win“. Choosing a suitable mission is a particularly difficult problem as you often don’t know how difficult a task will be until you are more than half complete.

Jane makes points about humans being happier when working hard and a desire for “epic meaning“. She says that it’s a problem that gamers believe that they can change a virtual world but not the “real world“. If you change the “virtual world” of software development then that changes the “real-world“.

Jane cites Herodotus as reporting a kingdom that was gripped in a famine for 18 years where the king instituted a policy of playing games and eating on alternate days with the aim being that the games would distract people from their hunger. I’m sure that I’m not the only person who’s gone without food or water for a day because of being too busy coding…

She has a lot of other interesting points and I recommend that you read the Institute For The Future [2] web site for more background information.

Now my question is, how can we encourage programmers to start doing Free Software and Open Source development and achieving some Epic Wins? I don’t claim to have good answers and I would appreciate any suggestions. If you blog about this please leave a comment on this post to direct readers to your blog.

Hacker Spaces

When in California last year I visited the NoiseBridge [1] Hackerspace. I was very impressed with what I saw, good equipment and very friendly people. The general concept of a “HackerSpace” is that it is an environment to support random creative projects. The first picture is a sign near the door which is clearly visible to anyone who is leaving, it encourages people to be “AWESOME” and “EXCELLENT” by cleaning up after themselves (and maybe others). I think that this demonstrates the core of what is needed to get such a community project going.

Generosity towards others was on display everywhere, there was some free fruit on a table as well as a bottle of Port for anyone to drink. Someone had written a note saying that it’s “not an insecure Port” (a computer security joke). Someone had created an artwork that resembled an advert which some idiots had mistaken for a terrorist bomb (the creature displaying the Impudent Finger).

The main (only?) phone in NoiseBridge is apparently a VOIP phone, it is located next to an old pay-phone along with some Magnetix and other toys that can be used by curious people of any age. Magnetix have had repeated safety problems that caused recalls so maybe such things are best placed in an 18+ environment.

When I visited about 10 people were working on electronics projects. There were a number of soldering irons in use and some serious test equipment (including a couple of CROs) was available. The people doing the soldering were eager to teach other people about their work. Other equipment that was available included some serious industrial sewing machines and some drill presses. A lot of that equipment is unreasonably expensive to buy for personal use and is also rather bulky to store, having it available in a central location is a great service for the community.

Finally Noisebridge has a lot of space. There are rooms that could be used for giving small lectures and couches in the central area for people to relax and have impromptu meetings. Of course they had wireless net access too.

Australian Hacker Spaces

Kylie Willison has written about the Adelaide Hackerspace which sounds promising [2].

The Connected Community Hackerspace is a new one in Melbourne [3]. It operates out of the homes of members so it’s not nearly as big as Noisebridge (which has a substantial property rented for 24*7 operation). I hope that we can get something running permanently in the Melbourne city area in the near future. The Noisebridge membership dues are $80 per month (or $40 for starving hackers). I would pay that for a comfortable chair in a convenient city location with net access surrounded by cool people!

Poster telling people that they are AWESOME and EXCELLENT if they clean upFree bottle of port with sign saying - this is not an insecure portVOIP phone in use, pay-phone for decoration, and MagnetixDrill presses and other heavy equipmentParts and CROs for electronic workRecreation of an advert that some idiots thought was a bombIndustrial sewing machineShelves full of random spare parts

Bose vs Bauhn/Aldi Noise Canceling Headphones

Me wearing Bauhn HeadphonesInside the case of Bauhn Noise Canceling Headphones showing the cable and connectorsOutside of the cases of Bauhn and Bose Headphones

Overview

The German supermarket chain Aldi has been running in Australia for 8 years now [1]. Their standard practice for a long time has been to offer regular special deals on a few items of consumer electronics every week, my chocolate fridge is one thing I bought from Aldi [2].

Today Aldi have started selling Noise Canceling Headphones [3]. These headphones are badged by Bauhn – but that name is apparently applied to random products from cheap manufacturers, it may be an Aldi name that is applied to stuff that they sell. The headphones cost $69AU which is really cheap. But the deal will probably end in less than a week when stock runs out.

Noise canceling headphones can be used in server rooms and other noisy environments. Every company that has a server room should buy a few sets. One of the features of noise-canceling is that it works best on low frequencies and on regular sounds – it specifically doesn’t block human voice well. In some noisy environments it will be easier to hear people talk if you wear such headphones!

Noise canceling headphones are also very useful to people who are on the autism spectrum and other people who get more annoyed by noise pollution than average people. I have been wearing my Bose headphones on public transport and when walking around in the city, this not only stops traffic noise but it also helps to avoid people thinking that I want to talk to them.

Features

The first picture shows me wearing the Bauhn NC headphones, it’s from the right to show the controls for the built-in MP3 player. I have not yet tested the MP3 functionality. It appears that as the controls are one power button, buttons for next/previous track, and for controlling the volume. This is fairly poor for MP3 functionality, ideally you would want to have a display to see a list of tracks, maybe have directories to store files, etc. I guess this could be a convenient feature on occasion, but you wouldn’t buy the headphones for the MP3 functionality.
The next two pictures show a comparison of the Bauhn headset with the Bose QC-15 headset that I bought last year [4].

The cases of the Bauhn and Bose devices are almost exactly the same size and of a very similar shape, the Bose case is tapered and indented and also has a finer weave on the cloth covering – it looks much nicer. Both devices come with an adapter for an airline socket and with a detachable cable. They also both have pouches attached to the inside of the case with velcro. But the Bauhn headphones come with an adapter for the 6.5mm TRS connector which could be convenient if you want to plug them in to a larger amplifier, the basic connector is 3.5mm in both cases. The Bauhn device uses a standard TRS connector at the headphone end while the Bose QC-15 use a special connector that matches the shape of the headset and which has a TRRS plug (to cater for the high/low volume switch), so it seems that a damaged Bauhn cable could be replaced cheaply while a replacement Bose cable would have to be purchased from Bose (presumably at great expense and delay). The Bauhn case also has a velcro attached pocket for storing business cards (or maybe a name tag or something).

The supplied cable for the Bauhn is described as being 5 feet long – which isn’t quite long enough to reach a tower PC that is sitting on the floor. The Bose has a cable that is about a foot longer (maybe 6 feet total), but due to the non-standard connector you can’t replace it. I presume that I could easily buy a 4 meter cable for the Bauhn headphones, but I could of course buy an extension cable to use with the Bose.

Bose advertise the QC-15 headphones as having 35 hours of battery life from a single AAA battery. Aldi advertise the Bauhn headset as having 5 hours of battery life when NC is turned on – and they use two AAA batteries. It’s widely regarded that rechargeable batteries don’t last as long as the batteries used for estimating the battery life (which presumably are the most expensive long-life batteries available). I’ve found a single rechargeable AAA battery to last well over 5 hours in my Bose headphones, so it seems that battery life is considerably worse for the Bauhn device.

One feature of the Bauhn device is that it can be used without any batteries for playing external music. The Bose headphones can’t be used at all without a battery. So while the Bauhn will use the batteries faster it will at least be usable when the batteries run out. But if you are buying headphones for the purpose of avoiding noise then the Bose headphones are simply better.

Comfort

The Bose headphones have significantly deeper ear wells than the Bauhn – about 23mm vs 18mm. If your ears stick out more than 18mm (as mine apparently do) then this is a good reason for choosing Bose.

The Bose headphones are a tighter fit, the spring that pushes the ear-pieces together is stronger. But they have better padding so this doesn’t cause me any discomfort. Also the Bose headphones have better passive noise reduction due to having a more snug fit around the ears. I’ve worn my Bose headphones on a flight from the US to Australia with hardly a break and they were quite comfortable – I would never want to do that with the Bauhn headphones.

Noise Reduction

I tested the Bose and Bauhn products against three noise scenarios, external music, an air-conditioner, and a car engine.

The Bose headphones made good reductions of the noise from the external music (Numb by Linkin Park) and the air-conditioner. The Bauhn headphones did little to stop Linkin Park and was not very effective against the air-conditioner noise. I think that this is largely due to the lack of passive noise reduction, the air-conditioner in question makes little vibration noise and the sound of rushing air is generally immune to active noise cancellation. Both headphones were very effective when in a car with the engine idling. The engine noise of vehicles seems to fall in an ideal frequency range for active cancellation.

Music Quality

When listening to Youtube music played on my Thinkpad I could not notice any quality difference between the two sets of headphones. I did notice that the Bose headphones seemed to have a greater response in the higher frequency range, but that doesn’t necessarily mean that one set is better than the other. Maybe if I was listening to FLAC0 encoded music that I had personally ripped from a CD then I would notice a difference. But for most people the Bauhn music quality should be good enough.

Design Quality

The Bose product is solidly designed, while the Bauhn product appears cheap in every way. Opening the battery compartment on the Bauhn headphones is difficult and if you do it wrong you could easily break the lid off, I expect that every set of Bauhn headphones that is used by children will be broken in a small amount of time – but it should still be fully functional with a broken lid. The matt finish of the Bose headphones should hide minor scratches much better than the shiny Bauhn headphones. The Bauhn headphones also have lower quality plastic parts, it appears that the molds used were designed cheaply and without adequate care to prevent marking the final product.

The design flaws that affect usage of the Bauhn product are the shallow ear wells, the poor fit of the cushions around the ears (which is probably mostly due to a weak spring pressing the ear cups to the wearer’s head), and the battery compartment lid which is difficult to open and appears prone to breakage. The other flaws are all cosmetic.

I wonder whether the Bauhn product was made by one of the big name manufacturers who deliberately reduced the quality to avoid competing with their more expensive products. It seems that the major flaws could have been corrected at design time with almost no increase in manufacturing costs.

Recommendations

If you can afford the Bose® QuietComfort® 15 Acoustic Noise Cancelling® Headphones then they are really worth the extra expense, I have no regrets at all about spending about $320US (including tax) on my Bose QC-15. The Bauhn product is good for when you want something cheap, for example a set to be used in a server room, or for the use of children. I bought a Bauhn headset for a friend who is a pilot, he spent $1,100 on a noise-canceling headset for his plane but had never got around to buying one for recreational use – I expect that he will allow his children to use his new Bauhn headphones, if they get broken it’s only a $69 expense.

The second cheapest NC headphones I’ve seen on offer in Australia is Harvey Norman selling Phillips HN-110 Noise Canceling Headphones for $100AU [5].

Amazon sells Philips HN 110 Folding Noise-Canceling Headphones for $50US but doesn’t seem to ship them outside the US (at least not to Australia).

JB Hifi also has some NC headphones on sale in Australia [6], but they are more expensive at $219 for AKG and $319 for Sennheiser. Also the models they sell are on-ear which means that they will inherently have very little passive noise reduction – and will also annoy anyone who doesn’t like having their ears squashed.

If I was buying NC headphones for my own use and didn’t want to spend $300US then I would either buy the Philips HN 110 Folding Noise-Canceling Headphones from Amazon and get a friend in the US to post them to me or I would buy them from Harvey Norman.

But the Bauhn product is good if you want cheap headphones to stop engine noise and give reasonable quality when playing music.

Links March 2010

Blaise Aguera y Arcas gave an exciting demonstration of new augmented reality mapping software from Microsoft that combines video (including live video) with static mapping data and pictures [1]. This is a significant advance over current mapping systems such as Google Earth – but it’s not released yet either. It will be interesting to see whether Google or Microsoft gets this released first.

The New York Review of Books has an insightful atricle by Garry Kasparov about human/computer chess [2]. It’s surprising the degree to which a combination of human and computer chess playing can give a good result. Amateur human chess players plus regular PCs can beat grandmasters with computers or high-end computers with human help. It’s apparently the quality of human-computer interaction that determines the quality of play. But the article contains a lot more, I recommend reading it.

Daniel Kahneman gave an interesting TED talk about the difference between experiential and memory happyness [3]. As the concept of the moment is so short (about 3 seconds) apparently most people try to optimise their actions for the best memories of being happy. But to do so requires some different strategies. For example a two week vacation gives a memory that’s not much different from a one week vacation. Therefore it seems that you would be better off staying in a five star hotel for a week than a four star hotel for two weeks, and eat dinner at a Michelin Star restaurant at least once per holiday even if it means eating at McDonalds on other occasions due to lack of funds.

Temple Grandin gave an interesting TED talk “The World Needs all Kinds of Minds” [4] which mostly focussed on teaching children who are on the Autism spectrum. She is concerned that autistic children won’t end up where they belong “in Silicon Valley”.

Anupam Mishra gave an interesting TED talk about how the people of India’s Golden desert built structures to harvest and store water [5]. Some of their ideas should be copied in Australia, due to mismanagement and stupidity Australians are failing to survive in much more hospitable places.

Michael Tieman wrote an insightful and well researched article about the OSI’s rejection of the IIPA’s attacks on Open Source [6]. This is worth reading by anyone who wants to make a business or social case for free software.

Mark Shuttleworth wrote an interesting post about the new visual style for Ubuntu and Canonical [7]. Apparently this includes the creation of a new font set which will be available for free use.

Divorced Before Puberty – an informative New York Times article by Nicholas Kristof about the links between treatment of women and terrorism [8].

The New York Times has an interesting article on “Human Flesh Searches” on the Internet in China [9]. It’s basically crowds targetting people to find private information and harass them (similar to what some griefers are known for doing on the English-language part of the Internet). But they seem more interested in vigilante justice than lulz.

The New York Times has an informative article about the Cult of Scientology (Co$) [10]. Among other interesting news it suggests that the number of cult victims in the US has dropped from 55,000 to 25,000 in the 2001-2008 time period. Senator Xenophon has called for an inquiry into the crimes committed by the cult and a review of it’s tax-exempt status [11]. As always Xenu.net is the authoritative source for information on the Cult of Scientology AKA the Church of Scientology.

The New York Times has an interesting article about formally studying the skills related to school teaching [12]. It largely focuses on Doug Lemov’s Taxonomy of Effective Teaching describes 49 techniques that improve school results and some other related research. The article also mentions that increasing teacher salaries is not going to help much due to the large number of teachers, it’s only professions that employ small numbers of people that can potentially have their overall skills improved by increasing salaries.

Andy Wingo wrote an interesting article about Julius Caesar [13] based on the book The Assassination of Julius Caesar: A People’s History of Ancient Rome by Michael Parenti. It seems that Caesar was more of a populist than a despot.

Interesting article in The Register about the Large Hadron Collider (LHC) [14]. Apparently one 3.5TeV proton beam has as much energy as a British aircraft carrier running at 8 knots.

Citing Wikipedia

A meme that has been going around is that you can’t cite Wikipedia.

You can’t Cite Wikipedia Academically

Now it’s well known and generally agreed that you can’t cite Wikipedia for a scientific paper or other serious academic work. This makes sense firstly because Wikipedia changes, both in the short term (including vandalism) and in the long term (due to changes in technology, new archaeological discoveries, current events, etc). But you can link to a particular version of a Wikipedia page, you can just click on the history tab at the top of the screen and then click on the date of the version for which you want a direct permanent link.

The real reason for not linking to Wikipedia articles in academic publications is that you want to reference the original research not a report on it, which really makes sense. Of course the down-side is that you might reference some data that is in the middle of a 100 page report, in which case you might have to mention the page number as well. Also often the summary of the data you desire simply isn’t available anywhere else, someone might for example take some facts from 10 different pages of a government document and summarise them neatly in a single paragraph on Wikipedia. This isn’t a huge obstacle but just takes more time to create your own summary with references.

When Wikipedia is Suitable

The real issue however is how serious the document you are writing is and how much time you are prepared to spend on it. If I’m writing a message to a mailing list or a comment on a blog post then I probably won’t bother reading all the primary sources of Wikipedia pages, it would just waste too much of my time. Wikipedia is adequate for the vast majority of mailing list discussions.

If I’m discussing several choices for software with some colleagues we will probably start by reading the Wikipedia pages, if one option doesn’t appear to have the necessary features (according to Wikipedia) then we may ask the vendor if those features are really missing and if so whether they will be added in the next version – but we may decide that we don’t really need the features in question and modify our deployment plans. Many business decisions are made with incomplete data, time is money and there often isn’t time to do everything you want to do. Using Wikipedia as a primary source for business decisions is a way of trading off a little accuracy for a huge time saving. This is significantly better than the old fashioned approach of comparing products by reading their brochures – companies LIE in their advertising!

When writing blog posts the choice of whether to use Wikipedia as a reference depends on the point that you are trying to make and how serious the post is. If the post isn’t really serious or contentious or if the Wikipedia reference is for some facts that are not likely to be disputed then Wikipedia will probably do. For some posts a reference to a primary source will be better.

A blog post that references data that is behind a pay-wall (such as a significant portion of academic papers and news articles) is practically of less use than a post that cites Wikipedia. In most cases Wikipedia references free primary sources on the Internet (although it does sometimes refer to dead tree products and data that is behind a pay-wall). In the minority of cases where the primary references for a Wikipedia page are not available for free on the Internet there will be people searching for freely available references to replace the non-free ones. So if you refer to a Wikipedia page with non-free references a future reader might find that someone has added free references to it.

The Annoying People

One thing that often happens is that an Internet discussion contains no references for anything – it’s all just unsupported assertions. Then if anyone cites Wikipedia someone jumps in with “you can’t cite Wikipedia“. If you want to criticise Wikipedia references then please first start by criticising people who state opinions as fact and people who provide numbers without telling anyone where they came from! The Guinness Book of Records (now known as “Guinness World Records”) was devised as a reference to cite in debates in pubs [1]. It seems that most of the people who dismiss references to Wikipedia on the net would prefer that Internet debates have lower requirements for references than a pub debate.

When Wikipedia is cited in an online discussion it is usually a matter of one mouse click to check the references for the data in question. If Wikipedia happens to be wrong then anyone who cares can correct it. Saying “the Wikipedia page you cited had some transcription errors in copying data from primary sources and some of the other data was not attributed, I’ve corrected the numbers and noted that it contains original research” would be a very effective rebuttal to an argument that relies on data in Wikipedia. Saying “you can’t cite Wikipedia” means little, particularly if you happen to be strongly advocating an opposing position while not providing any references.

If one person cites an academic paper and someone else cites Wikipedia then it seems reasonable to assume that the academic paper is the better reference. But when it’s a choice between Wikipedia and no reference then surely Wikipedia should win! Also references to non-free data are not much good for supporting an argument, that’s really just unverified claims as far as most people can determine – therefore the issue becomes how much the person citing the non-free reference can be trusted to correctly understand and summarise the non-free data.

Also it has to be considered that not all primary sources are equal. Opinion pieces should be considered to have a fairly low value and while they are authoritative for representing the opinion of the person who wrote them they often prove little else – unless they happen to cite good references which brings them to the same level as Wikipedia. The main benefit for linking to opinion pieces is that it saves time typing and gives a better product for the readers – it’s sometimes easier to find someone else expressing an opinion well than to express it yourself.

So please, don’t criticise me for citing Wikipedia unless others in the discussion are citing better references. If most people are not citing any references or only citing opinion pieces then a Wikipedia page may be the best reference that is being provided!

Xen and Debian/Squeeze

Ben Hutchings announced that the Debian kernel team are now building Xen flavoured kernels for Debian/Unstable [1]. Thanks to Max Attems and the rest of the kernel team for this and all their other great work! Thanks Ben for announcing it. The same release included OpenVZ, updated DRM, and the kernel mode part of Nouveau – but Xen is what interests me most.

I’ve upgraded the Xen server that I use for my SE Linux Play Machine [2] to test this out.

To get this working you first need to remove xen-tools as the Testing version of bash-completion has an undeclared conflict, see Debian bug report #550590.

Then you need to upgrade to Unstable, this requires upgrading the kernel first as udev won’t upgrade without it.

If you have an existing system you need to install xen-hypervisor-3.4-i386 and purge xen-hypervisor-3.2-1-i386 as the older Xen hypervisor won’t boot the newer kernel. This also requires installing xen-utils-3.4 and removing xen-utils-3.2-1 as the utilities have to match the kernel. You don’t strictly need to remove the old hypervisor and utils packages as it should be possible to have dual-boot configured with old and new versions of Xen and matching Linux kernels. But this would be painful to manage as update-grub doesn’t know how to match Xen and Linux kernel versions so you will get Grub entries that are not bootable – it’s best to just do a clean break and keep a non-Xen version of the older kernel installed in case it doesn’t initially boot.

A apt-get dist-upgrade operation will result in installing the grub-pc package. The update-grub2 command doesn’t generate Xen entries. I’ve filed Debian bug report #574666 about this.

Because the Linux kernel doesn’t want to reduce in size to low values I use “xenhopt=dom0_mem=142000” in my GRUB 0.98 configuration so that the kernel doesn’t allocate as much RAM to it’s internal data structures. In the past I’ve encountered a kernel memory management bug related to significantly reducing the size of the Dom0 memory after boot [3].

Before I upgraded I had the dom0_mem size set to 122880 but when running Testing that seems to get me a kernel Out Of Memory condition from udev in the early stages of boot which prevents LVM volumes from being scanned and therefore prevents swap from being enabled so the system doesn’t work correctly (if at all). I had this problem with 138000M of RAM so I chose 142000 as a safe number. Now I admit that the system would probably boot with less RAM if I disabled SE Linux, but the SE Linux policy size of the configuration I’m using in the Dom0 has dropped from 692K to 619K so it seems likely that the increase in required memory is not caused by SE Linux.

The Xen Dom0 support on i386 in Debian/Unstable seems to work quite well. I wouldn’t recommend it for any serious use, but for something that’s inherently designed for testing (such as a SE Linux Play Machine) then it works well. My Play Machine has been offline for the last few days while I’ve been working on it. It didn’t take much time to get Xen working, it took a bit of time to get the SE Linux policy for Unstable working well enough to run Xen utilities in enforcing mode, and it took three days because I had to take time off to work on other projects.

Maintaining Screen Output

In my post about getting started with KVM I noted the fact that I had problems keeping screen output after the program exits [1].

The following snippet of shell code demonstrates the solution I’ve discovered for this problem. It determines whether SCREEN is the parent process of the shell script and if so it sleeps for 60 seconds before exiting so I can see the KVM error messages. The other option is for the script to call “exec bash” to give me a new shell in the same window. Note that if I start a screen session and then run my KVM script I don’t want it to do anything special on exit as I will return to the command-line in the same window. If I run “exec kvm-unstable” or have a system boot script run “start-stop-daemon -S -c USER --exec /usr/bin/screen -- -S kvm-unstable -d -m /usr/local/bin/kvm-unstable” then on exit I will be able to see what happened.

#!/bin/bash
set -e
kvm ETC || echo “KVM gave an error return code”
COUNT=$(ps aux|grep $PPID|grep SCREEN|wc -l)
if [ "$COUNT" = "1" ]; then
  echo "screen is the parent"
  sleep 60
else
  echo no screen
fi

Update: Thanks to John for the Slee for suggesting the following:
#!/bin/bash
set -e
kvm ETC || echo “KVM gave an error return code”
if grep -q SCREEN /proc/$PPID/cmdline ; then
  echo "screen is the parent"
  sleep 60
else
  echo no screen
fi