PETA’s Claims

PETA claims that “many autistic kids improve dramatically when put on a diet free of dairy foods” [2]. They also speculate about the possibility of Autism being caused by dairy.

One thing that confuses the issue is the impact of stress on people with Autism Spectrum Disorders (ASDs). Whatever you are trying to do you will probably do it less effectively if under an excessive amount of stress, and the background stress levels of people on the Autism Spectrum tend to be quite high at the best of times. So add in some extra stress from a food allergy and the ability to emulate an NT can decrease a lot.

There are people who make credible claims about significant behavior improvements in Autistic children after changing their diet. Eliminate foods that trigger a minor allergic response and the behavior of NT kids will improve too.

I’m sure that there are some Autistic kids who have a minor intolerance to lactose or casein who’s behavior would improve if they had no dairy products. There are probably just as many Autistic kids who have a minor allergy to peanuts who would get the same benefit from avoiding peanut butter. It’s not inconceivable that some Autistic people may be allergic to soy or wheat and find that they can cope better if their consume more milk, cheese, and steak and less vegetables!

Also some people on the Autism Spectrum have a better sense of smell than NTs, and it’s fairly common to be more “fussy” about the appearance of food. Force children to eat food that smells bad and their behavior might deteriorate.

The issues of diet and Autism are more difficult than those of vaccines because while people just imagine the vaccines to have a bad affect, there are people who are proven to get a bad affect from certain foods.

Some Ideas for Research

I think that the biggest problem with PETA’s research in this regard is citing a study of only 20 individuals and only testing the removal of milk. A proper study would involve more subjects (maybe 100) and separate tests of removing milk, eggs, wheat, rice, seeds, nuts, soy, fish, spices, and food colorings and additives.

It would also test various methods of reducing stress, having a more quiet environment etc.

PETA do deserve some credit for leaving this URL in the comments [3], it’s a study that disproves the link between milk and Autism. But it’s still a small sample size of 14.

Why They Target Autism

In spite of psychologists moving to define Asperger Syndrome and Autism as the same thing, the people who make such claims aren’t talking about people like me. They want to make claims about people who can’t refute them, such as people who fit the Rain Man stereotype. The Low Functioning Autistic (LFA) people have less ability to communicate and are easier to ignore, so if you want to make some stuff up about a group of people then they are an easy target.

Parents of LFA kids are often desperate and will latch on to any idea that seems to help. They can imagine that things have improved in spite of a lack of evidence and also fail to realise that children can improve rapidly just due to their natural development, 1 month is not much time for an adult but for a 4yo it’s 2% of their life!

Also any supposed research that includes testimony of parents should be regarded as rubbish. If you talk to any child psychologist they will tell you about how difficult it is to convince parents that their child is on the Autism Spectrum, a Google search for “autism” + “denial” also brings up plenty of hits. Parental denial doesn’t stop at refusing to accept a diagnosis, it includes wanting to reject it at any later time based on any shred of evidence that may be available. So when there is a diet change or some other supposed cause followed by some apparently better behavior they want to claim that Autism is cured.

I’ve written a document titled “Some Suggestions for Parents of Aspies” [4] which is largely based on the childhood memories and adult experiences of various Aspies. My document covers many issues and few kids on the Spectrum will benefit from all of them, but I think that there is something there that can benefit every child on the Spectrum – and probably a lot of geeky NT kids too. It seems to me that when dealing with Autistic kids it’s a lot better to seek advice from adults on the Autism Spectrum than from random Neuro-Typical people (NTs), particularly if those NTs happen to have an agenda to push. The sensible parents are the ones who seek advice from psychologists and people like me rather than from random unqualified NTs.

• [1] http://jamespurser.com.au/blog/stop-using-autism-push-your-own-brand-lunacy
• [2] http://www.peta.org/features/got-autism-learn-about-the-link-between-dairy-products-and-the-disease.aspx
• [3] http://www.reuters.com/article/idUSTRE64I6EZ20100519
• [4] http://doc.coker.com.au/aspie/suggestions-parents-aspies/

Related posts:

1. Communication Shutdown and Autism The AEIOU Foundation The AEIOU Foundation [1] is a support...
2. Autism vs Asperger Syndrome Diagnostic Changes for Autism Spectrum Disorders Currently Asperger Syndrome (AS)...
3. Conferences and People on the Autism Spectrum There have been some recent discussions about issues related to...

The free offering only provides 15G of free data transmission and 15G of free data reception per month. For my blog server that would be more than adequate as it has sent 24.5G and received 14G over the last 75 days.

The Cost of Disk IO

The offer requires that you sign up with a credit card so if you use more than the free capacity then you have to start paying. It seems that the main issue in this regard is disk IO.

The only storage that is available for a micro instance is the Elastic Block Store (EBS) [3]. The main way that EC2 operates is that when you create a new virtual machine it copies the data from an existing image so you can easily create dozens or hundreds of virtual machines with local disk performance – and the data is removed when the instance is shut down. EBS is essentially SAN based storage, it’s persistent and operates like a regular disk.

The pricing for EBS is $0.10 per allocated GB per month plus $0.10 per million IOs. Unfortunately they don’t define what an IO is apart from mentioning that you can use IOSTAT to measure them. According to iostat the server running my blog is doing 0.99 tps, so that means in a 30 day month I would expect 30*24*3600*0.99 = 2.56M transactions. Iostat also tells me that my blog server has read 62075330 blocks and written 91683344 blocks over the last 75 days 16 hours of uptime, that means it would do about (62075330+91683344)/75.66*30 = 61M block transfers in a 30 day month. So if I was to run my blog server on EC2 I could be spending either $0.15 or $6.00 per month on disk IO depending on how they count it (or maybe something in between, something larger than a 512 byte block but smaller than a “transaction” as reported by iostat could be used). Given that the last time I checked the prices one could rent a DomU for less than $6 per month [4] the difference in possible ways of measuring IOs is very significant!

The MySQL server that is the backend to my blog (as well as a few other things) seems to be averaging about 3 writes per second (and no reads during operation because the databases are small). So it might be another 5 million IOs per month for the database.

It’s unfortunate that Amazon haven’t clearly specified what they mean when measuring IO for billing purposes. Some aspects of measurement such as whether the bills for bandwidth include Ethernet headers can be ignored as a 26 byte Ethernet header won’t make much difference to the bill when the average packet size is around 400 bytes or more (from ifconfig output it seems that my blog server sends packets of an average size of 459 bytes and receives packets of an average size of 1250 bytes). But the methods of measuring disk IO could give a factor of 20 difference in the bill.

Optimising for EC2

If I was going to put my blog on EC2 then I would start by configuring Apache to log to a fifo and then write a daemon that stores the log data and allows my home server to poll it and get the log data. As the filesystem is already mounted with noatime it seems that writing logs is the cause of all the disk writes so if they were stored in RAM (which shouldn’t be a problem with 4M of logs per day) then all those writes could be avoided. Another possible solution to this would be to make /var/log be a tmpfs and then rsync the files periodically to my home server. I don’t really need to have all the logs remain on the server I just need them to remain somewhere.

Amazon also offers 100,000 messages on their Simple Queue Service (SQS) for free [5]. The messages can be up to 8K in size and are stored for up to 4 days. So it seems possible to put Apache logs into SQS messages in bundles of less than 8K and then get them out later for transfer to a server outside EC2.

If I was able to get my disk writes to almost zero then there’s a good chance that I could get into the free zone for one year.

Conclusion

Would I use this service? If I was looking for new hosting for my blog then I would seriously consider it. EC2 is quite fast and well connected and depending on how they work out the billing for disk IO I could probably keep the cost close to zero.

EC2 is a different way of running things so you can’t just have a virtual server running and expect it to automatically restart if it goes down for any reason (a standard feature of virtual hosting companies). Amazon does have a range of tools for managing EC2 instances and they all seem to be available in the free trial. So after spending the time to learn those tools the result should be good.

I think that there are two groups of people who could benefit from using this. One is hobbyists, this is a great way to learn some skills related to high-end server stuff and EC2 experience should look good on a CV. The other is companies who want to use EC2 anyway and who will just save some money that they would otherwise pay. I’ve seen someone recommend the free offering from EC2 for a company that needed a small server, I think that isn’t a good option as a company that only wants a single small server will be better off paying something between $5 and $20 per month for a DomU from one of the virtual hosting providers.

After a year you have to pay regular prices. A micro instance costs $0.02 per hour which is $14.40 per month, SQS costs $0.10 per month for sending up to 1G of data in and at $0.01 per 10,000 SQS requests would costs $0.03 (the 4M of log data I generate per day would be 1000 requests to write and read it which would be 30,000 requests per month), the EBS for MySQL would cost $0.10 for 1G of storage and maybe $0.50 for IOs. That means $15.13 before counting bandwidth.

My blog server averages just under 10G of transmitted data per month, the first Gig is free so that would cost $0.15 for each subsequent Gig which is $1.35 per month. It receives just under 6G per month which at $0.10 per gig would be $0.60. So including data transfer it would be about $17.08 per month.

This is a lot more expensive than some of the cheaper virtual server offerings but admittedly the cheaper virtual offerings don’t have as much RAM. Also with a blog instance running on EC2 I could easily configure it so that I could create some big instances that use the same MySQL database if a lot of extra traffic suddenly started arriving. A micro instance running MySQL on it’s own could cope with a heap of load a lot more easily than the PHP code for my blog. So using bigger servers to run the PHP code while running MySQL on the same server would be a good option – particularly if the bigger servers use caching.

Finally if you want to run an EC2 instance for a year then you can get a reserved instance, you pay $54 per annum and the cost drops to $0.007 per hour instead of $0.02 per hour. Using a reserved instance for my blog would give a cost of $54+365*24*0.007+12*(0.10+0.03+0.10+0.50) or about $124.08 per annum. $10 per month isn’t too bad. So if I migrated my blog to EC2 then I would probably keep it there after the free period expired. The ability to expand rapidly when necessary is worth paying extra. Of course I am making some assumptions such as that the performance of a micro instance doesn’t totally suck – as Amazon don’t specify what bursting to 2ECU really means it could have some performance problems.

Note that all prices in this post are in US Dollars.

• [1] http://aws.amazon.com/free/
• [2] http://aws.amazon.com/ec2/
• [3] http://aws.amazon.com/ebs/
• [4] http://etbe.coker.com.au/2010/06/22/virtual-hosting-prices/
• [5] http://aws.amazon.com/sqs/

Related posts:

1. New Servers – a non-virtual Cloud NewServers.com [1] provides an interesting service. They have a cloud...
2. Improving Blog Latency to Benefit Readers I just read an interesting post about latency and how...
3. Getting Started with Amazon EC2 The first thing you need to do to get started...

Lisa of Chaotic Idealism wrote an interesting post about the NT social bias [3]. In summary NTs seem to think that Autism Spectrum Disorders are only about socialisation, not realising that for many people on the Spectrum it’s sensory issues that are their main problem. Social problems are exacerbated by sensory issues and other causes of stress, so I think it’s worth considering ways in which conferences can be planned to be less stressful for people on the Autism Spectrum, people who have SPD [4] that isn’t associated with an ASD, and NTs who just get annoyed by loud noises etc.

What Autism Conferences Do

Autscape is one of only two conferences for people on the Autism Spectrum and the only one which clearly documents how they plan their conference [5]. The first noteworthy thing that they do is have badge colors to indicate what level of social interaction is desired by each delegate, I don’t think that this is relevant to Free Software conferences as people who don’t have sufficient social skills to suit at least a green badge probably won’t be attending. But I think that when attending a conference about Free Software or any other equally geeky topic (if there is an equally geeky topic) it’s worth keeping in mind the fact that there are probably a lot of people who would like to talk to you but lack the social skills to start a conversation.

The next thing that they document is a black circle badge which indicates that the wearer shouldn’t be photographed. Prior to reading that web site I wasn’t aware of this being an Autistic issue, I was only aware of it being an issue for women who don’t want zoomed-in pictures of themselves appearing on guys web sites (even pictures that aren’t up-skirt or down-blouse can be unwelcome). A conference policy that prohibited photographs that zoom in on one person without that person’s consent (or parental consent in the case of minors) would probably be a good idea.

Another thing about badges is that it’s a really good idea to have the delegate’s name on both sides of the badge if the badge is attached in a way that permits it to turn. People on the Autism Spectrum tend to have some difficulty in recognising people and in remembering names. I find it inconvenient when someone expects me to recognise them but has their badge turned around so I can’t see their name. Some people get really unhappy if they think that someone doesn’t recognise them.

Autscape has long breaks between activities and a leisure session each afternoon to allow delegates to recover from the stress of dealing with people. It seems to me that computer conferences in some cases could do with longer breaks between sessions. I find that a lot of the benefit of a conference is in what happens outside sessions and the standard practice of publishing videos of presentations makes personal meetings a more important part of the conference.

Autscape has designated quiet spaces. I think that for computer conferences which have hack-labs (which seems to be most Free Software conferences nowadays – even if they aren’t labelled as such) it would be good to have some lab areas designated as quiet zones. I think that it is a really good thing to meet people you’ve only known by email and then play some LAN based games against them and that this should be encouraged as part of a conference, but having that sort of thing separated from people who want to do some quiet coding is a really good idea. Whether people want to do quiet coding, read email, or just escape from the stress of a conference a quiet hack-lab would be a good place for it.

An issue that’s related to quiet spaces is the ability to escape from social situations. One of my pet hates is corporate meetings on boats, when the boat is in motion there is no escape. Corporate meetings that are only accessible by coach are also bad. Fortunately most conferences aren’t like that.

The Autscape web site states that they prohibit people from wearing perfume or aftershave to help people who are sensitive to smell. My observation of Free Software conferences is that encouraging everyone to have a shower every morning would be a good idea as there are stronger smells from unwashed people than from perfume.

One thing that’s interesting about the Autscape web site is that they have different color schemes available and have tested it in multiple web browsers – including Safari and Konqueror (which apparently don’t work so well). It’s interesting to note that they test with such a variety of browsers including free software ones – most corporations don’t do that.

Sensory Processing Issues

The main SPD issues related to conferences seem to be noise and light related.

For social events one difficulty that most people on the Spectrum seem to face is in listening to one person in a noisy crowded room. As well as that sudden noises and loud background noises can be very stressful. While it’s sometimes impossible to avoid crowds (which can be another problem) it is often possible to select venues that have less noise problems. A venue with carpet on the floor and soft walls (anything other than brick or concrete) will be a lot quieter than one with hard surfaces that reflect noise. It seems that a quiet venue will benefit NTs as well, there seems to be a strong correlation between the price of food at restaurants and the amount of sound absorbing material on the floor and walls – people who can afford a good dining experience seem to want it quiet.

In terms of visual issues the relevant problems seem to be related to sudden transitions and lecture halls that are extremely dark. The only thing that can be done by conference organisers is to seek to have the lights in the lecture halls as bright as possible without preventing the viewing of the projector screen, this is usually done anyway.

For social events the whole binge drinking at crowded bars thing doesn’t work too well due to noise, poor lighting, crowds, and the smell of vomit. But there’s no shortage of reasons to discourage binge drinking at conferences.

Food

Psychology Today has a good article about preferences for food and “picky eaters” [6]. Lots of people on the Autism Spectrum have similar issues. The thing to do when arranging a conference meal is to have things neat and without needless combinations. Think about making food look more like what you would expect to see in a Japanese restaurant and less like Paella. Also having some very plain food on offer is a good thing, I think that bread-rolls for dinner and ice-cream for desert makes a viable meal. But any dish with a word like “hash” or “mixed” in it’s name isn’t a good option. Finally some combinations are really bad, I always find rare steak and potatoes on the same plate to be rather disgusting – potato that’s blood-stained doesn’t appeal. The majority of conference meals satisfy these criteria.

Autscape provides options of eating outside the main dining hall for people who can’t tolerate the noise. For a Free Software conference it might be a better idea to provide seating outside the main area for people who are going to make noise. I don’t mind people who want to get really drunk at the conference dinner, but I would prefer them to be in a separate room. Also when assisting a drunk friend to leave the venue before they cause more problems it would be convenient if there was a good place to take them to. The one occasion when I had to strongly encourage a friend to leave a conference dinner to reduce his embarrassment the next day (and reduce the annoyance for everyone else) there was no good place to take him – so he just came back!

Conclusion

I don’t expect that anyone will make any significant changes to conference plans after reading this post. I have tried to focus on things that would benefit NTs as well, but there are practical issues that get in the way such as the cost and availability of venues that are large enough. But there are some smaller ideas that can be implemented with relative ease.

I hope that the people who are making claims about Autism and conference behavior will refer to this in future. If you think that there is a problem with the way people on the Spectrum act at conferences then the solution will more likely involve the suggestions I make here than anything else.

• [1] http://etbe.coker.com.au/2010/12/03/aspie-social-skills-free-software/
• [2] http://etbe.coker.com.au/2010/12/08/empathy-autism-and-geeks/
• [3] http://chaoticidealism.livejournal.com/88097.html
• [4] http://en.wikipedia.org/wiki/Sensory_processing_disorder
• [5] http://www.autscape.org/experience/autisticneeds
• [6] http://www.psychologytoday.com/articles/201101/accounting-taste

Related posts:

1. meeting people at Linux conferences One thing that has always surprised me is how few...
2. Empathy, Autism, and Geeks LWN has a recent article titled “The dark side of...
3. Autism vs Asperger Syndrome Diagnostic Changes for Autism Spectrum Disorders Currently Asperger Syndrome (AS)...

One interesting feature of the program is that it doesn’t match requests and replies. I presume this is because any firewall that only allows one reply per echo request will probably ensure that the reply contents match the request contents, so they just assume that a firewall will let all ICMP echo/reply traffic through. The upside of this is that it should give lower round trip times than any tunneling system that polls for return data.

I’ve filed some Debian bug reports about it, bug #609413 is a request for it to set icmp_echo_ignore_all when it’s running and also emulate the regular PING functionality. Bug #609412 is a request for it to assign the IP address to the tun0 interface. Bug #609414 is a request for the server side of it to call daemon(0,0).

I won’t leave this running. Having to run a virtual server with the regular ICMP functionality disabled is too much effort for the small benefit that using ICMP tunneling may offer over DNS tunneling.

My configuration scripts (with the IP address removed) are below.

Configuration

Server

#!/bin/sh
set -e
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all
icmptx -s SERVERIP &
sleep 0.5
ifconfig tun0 mtu 65535 10.10.10.1 netmask 255.255.255.0

Client

#!/bin/sh
set -e
killall icmptx || true
icmptx -c SERVERIP &
sleep 0.5
ifconfig tun0 mtu 65535 10.10.10.2 netmask 255.255.255.0
wait

Related posts:

1. ARP In the IP protocol stack the lowest level protocol is...
2. ssh tunneling of email On a Debian mailing list someone claimed that it was...
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I was considering renewing my Three contract and getting a HTC Desire HD [1]. What I need is a phone that is good for being a ssh client on 3G networks, has a good camera, and has all the fancy Google Apps.

In the comments Lon recommended a Norwegian review of phone cameras which gave the Sony Ericsson Xperia X10 a much better review than the HTC Desire HD [2] – the Xperia was the highest rating Android camera phone while the Nokia N8 was the best overall.

Also the Xperia is a lot cheaper, I can get it on a $29 monthly cap from Virgin as opposed to $44 per month from Three. So just on hardware and price the Xperia beats the Desire HD.

One of the advantages of the Xperia from Virgin being cheap is that my wife and I can use the same model of phone. This avoids having to solve two sets of phone related problems and also allows us to do things like swap batteries between the phones based on who can most conveniently charge their phone.

The Need for Root

But one problem with e Xperia is that the CyanogenMod images for rooted Android phones can’t be installed on an Xperia because the boot loader hasn’t yet been cracked [3]. I would like to run CyanogenMod so I can get wireless proxy support, and support for tunneling IP over DNS, ICMP, and OpenVPN.

The Three web site claims that they have 3G phone and net access in Bendigo, but on a recent holiday my phone said that it was “roaming” all the time and I couldn’t get net access. I ended up having to use McDonalds Wifi net access which had ports such as 22 blocked and thus forced me to use Iodine IP over DNS to get proper net access. To avoid having to talk my mother through rebooting servers in future I need to have a mobile ssh client that can use all possible protocols. I could carry my EeePC with me all the time, but sometimes it’s good to travel light.

OTOH, as I feel compelled to fiddle with all my computers it would probably give me a more reliable mobile experience if I was unable to mess with my phone.

Why Buying a Phone Outright Isn’t Viable

A $29 monthly plan is probably the cheapest plan that will do for anyone who uses a phone regularly, I have had a Three $29 plan for the last four years which allows up to $150 of calls to be made in a month and typically use about $60. So any plan which doesn’t have such a cap will have to be no more than half the price of Three on a per-minute basis to compete. If I’m going to pay $29 per month ($696 over a 24 month contract) then I can use a free phone. If I was to buy a phone then it would cost at least $500 for anything that I like and maybe a lot more.

Buying a phone independently of a contract would about double the cost of owning a phone. It’s really not a viable option.

Therefore I am compelled to buy a phone that is on offer from a Telco. Things like the Nokia N900 are nice devices but as the Telcos don’t offer them I can’t consider them.

No Discount if you Don’t get a Phone

The annoying thing is that the Telcos don’t offer a discount if you choose not to get a phone. Obviously buying the hardware costs them some money, so a $29 cap with a phone included should have a matching offer of something less than $29 if you choose not to get the phone from them. I currently have a $29 per month contract with Three, I can renew that for another two years at the same rate and get a half-decent phone for “free” or I can renew for two years on a $19 per month contract and get a low-end phone for “free” but I can’t get a price that is lower than $19 per month if I decide to keep my current phone.

If Three was to offer such a discount then I would consider buying a phone outright over the net and staying with them. But as it is they don’t provide good deals for buying a phone and give me an economic incentive to go to another provider. So I will probably use Virgin when my contract runs out in January.

Locked Phones

Many Telcos still sell locked phones on a contract. When that happens it’s really difficult to get a phone unlocked as the Telco employees usually aren’t very helpful. There are a variety of web sites claiming to generate unlock codes for phones, most seem to charge $10 or more for this service and the free ones have a very small range of phones, so getting the unlock code from the Telco seems to be the only option for a phone at the end of it’s contract period as it’s not worth enough to justify the $10 expense.

While some Telcos sell unlocked phones on plans the ones that lock their phones have a chilling effect on the industry. Most people don’t test whether their old phone can be used with a different provider they just throw it out – the phone stores conveniently provide bins for old phones that are apparently recycled for some good cause.

Conclusion

If you make serious use of mobile phones (EG being ready to fix errors reported by Nagios 24*7) then choosing a new phone and plan is one of the most difficult things there is to do. All the plans are quite complicated and every Telco offers a different set of phones. The Telco web sites are usually poorly done, most of them don’t have an option to search for Android phones or for phones with a certain minimum resolution – they usually don’t even state the resolution and use terms such as WQVGA which don’t even have a fixed meaning in pixels. When it comes to choosing a plan most Telcos don’t have a clear comparison of the different plans, writing your own spreadsheet comparing plan costs is a good idea.

The fact that Telcos such as Virgin and Three/Vodaphone allow free calls to other people using the same company makes it even more tricky. I have to discuss my phone plans with several relatives as there is a good incentive for everyone to use the same provider.

I think that we need government regulation on the way that phones are bundled. The market for phones that aren’t associated with Telco contracts has been destroyed by the anti-competitive behavior of the Telcos.

• [1] http://etbe.coker.com.au/2010/11/17/mobile-phone-sysadmin/
• [2] http://www.amobil.no/artikler/norges_beste_kameramobil/79081
• [3] http://www.cyanogenmod.com/

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2. Old Mobile Phones as Toys In the past I have had parents ask for advice...
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My SE Linux Play Machine has been down for a couple of weeks. I’ve changed to a cheaper Internet access plan which also allows me to download a lot more data, but I don’t have a static IP address any more – and my ISP seems to change the IP a lot more often than I’ve experienced in the past (I’m used to having a non-static IP address not change for months rather than hours). So I needed to get Dynamic DNS working. Naturally I wasn’t going to use one of the free or commercial Dynamic DNS solutions, I prefer to do things myself. So my Play Machine had to remain offline until I fixed this.

The Solution

dyn    IN      NS      ns.sws.net.au.
        IN      NS      othello.dycom.com.au.
play    IN      CNAME  play.dyn.coker.com.au.

The first thing I did was to create a separate zone file, I put the above records in my main zone file to make play.coker.com.au be a CNAME for play. and dyn.coker.com.au is a dynamic domain. I have SE Linux denying BIND the ability to write to the primary zone file for my domain to make it slightly more difficult for an attacker to insert fake DNS records (they could of course change the memory state of BIND to make it serve bogus data). The dynamic zone file is stored where BIND can write it – and therefore a BIND exploit could easily replace it (but such an attack is out of the scope of the Play Machine project so don’t get any ideas).

Another reason for separating the dynamic data is that BIND journals changes to a dynamic zone and therefore if you want to manually edit it you have to delete the journal, stop BIND, edit the file, and then restart BIND. One of the things that interests me is setting up dynamic DNS for some of my clients, as a constraint is that my client must be able to edit the zone file themself I have to keep the editing process for the main zone file relatively simple.

dnssec-keygen -a hmac-md5 -b 128 -n host foo-dyn.key

I used the above command to create the key files. It created Kfoo-dyn.key.+X+Y.key and Kfoo-dyn.key.+X+Y.private where X and Y are replacements for numbers that might be secret.

key "foo" { algorithm hmac-md5; secret "XXXXXXXX"; };
zone "dyn.coker.com.au" {
  type master;
  file "/var/cache/bind/dyn.coker.com.au";
  allow-update { key "foo"; };
allow-transfer { key ns; };
};

I added the above to the BIND configuration to create the dynamic zone and allow it to be updated by this key. The value which I replaced with XXXXXXX in this example came from Kfoo-dyn.key.+X+Y.key. I haven’t found any use for the .private file in this mode of operation. Please let me know if I missed something.

Finally I used the following shell script to take the IP address from the interface that is specified on the command-line and update the DNS with it. I chose a 120 second timeout because i will sometimes change IP address often and because the system doesn’t get enough hits for anyone to care about DNS caching.

#!/bin/bash
set -e
IP=$(ip addr list $1|sed -n -e "s/\/.*$//" -e "s/^.*inet //p")
nsupdate -y foo:XXXXXXXX << END
update delete play.dyn.coker.com.au A
update add play.dyn.coker.com.au 120 A $IP
send
END

Update

It is supposed to be possible to use the -k option to nsupdate to specify a file containing the key. Joey’s comment gives some information on how to get it working (it sounds like it’s buggy).

rhesa pointed out another way of doing it, so I’ve now got a script like the following in production which solves the security issue (as long as the script is mode 0700) and avoids using other files.

#!/bin/bash
set -e
IP=$(ip addr list $1|sed -n -e "s/\/.*$//" -e "s/^.*inet //p")
nsupdate << END
key foo XXXXXXXX
update delete play.dyn.coker.com.au A
update add play.dyn.coker.com.au 120 A $IP
send
END

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