On the upside, the server room isn’t on fire.

December 8th, 2016 by
This is not the correct way to mix servers and water based fire suppressant.

This is not the correct way to mix servers and water based fire suppressant.

One of our customers does embedded development and have some custom servers in their office as a build platform. This is hardware specific to the embedded designs they’re working on and they can’t locate it in a data centre as they require regular human attention. Unstable development drivers cause crashes and the root flash filesystems need to be re-imaged and replaced.

Recently they’ve moved office and their new office has a ‘server room’, ideal for putting their very expensive custom kit in, and a handful of other machines that they keep locally in the office. While doing the fit out, they noticed that their ‘server room’ is attached to the main sprinkler system. A fire in the building and whilst the bread may be saved from being overly toasted, their expensive hand built development boards are drowned.

They raised this with their landlords who billed them the best part of a thousand pounds to resolve the problem, see the picture on the right.

I’m not sure if it’s the belief that the plastic roof will help, the combustible struts to hold it up or the lack of guttering that really emphasises the mismatch between what a landlord things a server room looks like and what a real data centre actually provides.

We’re in further discussions to see if we can host their custom kit too, because our server room has non computer damaging halon as a fire suppressant and we will return the servers to them unwashed. If your office server room looks like this, please get in touch at sales@mythic-beasts.com.

I know that I know nothing

May 13th, 2016 by
Over a thousand people put together 43000 packages which forms the universal operating system.

Over a thousand people put together 43000 packages which forms the universal operating system.

One of the hazards of going to the pub in Cambridge is that very smart people will occasionally ask you difficult questions. Steve McIntyre, a former Debian Project leader asked our advice as to how Debian should specify a new central build server. Did we think that they’d be best off with lots of RAM or fast SSD, was PCI-E attached SSD better than SATA SSD or even sticking with cheap, slow but very large spinning hard disks.

On the unusual occasions we build software it completes very quickly, and for any big complicated package we’d just install the binary package from Debian. Advice that is almost always spot on, unless you are Debian attempting to make the binary packages in the first place.

We thought about this for a short time and proclaimed confidently that we didn’t know the answer.

However in Mythic Beasts we have a very strong science background. We suggested the right plan was to test it, take a big machine with multiple types of storage, disk, SATA attached SSD and PCI-E flash and try it out. Shortly afterwards our brain kicked in and realised that this looked just like the new VM hosts we were commissioning and with only a slight rearrangement to our plans we could lend one to Debian. Some weeks of work later and the answer is that an SSD makes a huge difference for the working filesystem, otherwise it doesn’t matter.

Without the hot air

April 15th, 2016 by

It’s with great sadness we learned of the death of Prof Sir David MacKay, FRS. He taught three of the Mythic Beasts founders information theory in 1999–2000, a fascinating and stunningly well-lectured course. The textbook Information Theory, Inference, and Learning Algorithms is freely available to download. Prof MacKay believed it was possible to make the world a better place.

Energy policy done by the numerate.

David’s other textbook Sustainable Energy, is not only fascinating, but vital reading for anyone interested in energy policy. It’s excellent, not because it provides answers, but because it teaches the tools to work things out. Can we power the UK only from wind energy? No. Can it make a substantial contribution? Yes, If we built lots and lots of wind how much can it contribute? Hopefully around 25% if you include a lot of offshore.

If more people read and understood the book we’d have fewer articles about the amazing solar panels that create power from rain, when the abstract tells us they create micro amps and milli-volts, throwing away 180W/m2 of solar to create 0.000000001W/m2 from rain.

David’s website withouthotair.com is prepaid far in advance and will remain available for many years to come.

The problem with the youth of today is hard work and excessive talent

February 1st, 2016 by

Almost a decade ago in 2006 Eben showed off his Raspberry Pi protoype with the original aim being to improve the standards of computer science for Cambridge University Computer Science students. Four years ago the Raspberry Pi launched, and the first post-pi generation of students are now in their final year. Today I went back to the Computer Science department to deliver a lecture for their e-commerce course on web application architecture and scaling. Several of the examples were taken from scaling of the Raspberry PI website – a website literally built with the aim of educating the students sat directly before me.

One students in the room was Will Shackleton. Will came over after the lecture to show me one of his projects, he’d taken my original Upside-down-ternet project for messing with my neighbours who stole my wifi, and turned it into an android app, Network Spoofer that you can use on wifi networks.

His first implementation embedded a Debian chroot with my original terrible perl script and squid before he reimplemented it properly with a proper proxy and parser to enable many more features and cleaned it all up. We discussed some issues – e.g. evil hosting providers like us enabling free SSL which prevents intercepting connections, how a sense of ethics is important – Will has refused to implement SSL strip – and I gave my sketch idea of how to do an IPv6 gateway version that wouldn’t require arp spoofing.

So The Youth of Today are taking the things we built, cleaning up the messes we left behind and making things better.

PiZero won!

December 10th, 2015 by
Pi Zero, 2p for scale, not included with prize.

Pi Zero, 2p for scale, not included with prize.

Last week we started a competition to win a Pi Zero. We’ve had a small number of entries, half from school age people eligible to win, the other half from entertained techies. We’ve also been using this as a job filter for some time so we have a rich depth of existing answers.

The competition is very simple, our web-page generates a mathematical sum for you to work out the answer to, and in order to succeed you have to send us the answer within one second. It’s an anti-turing test – a person can’t do it but a computer can. When you’ve succeeded we ask you to send us the code. This gives two important things, a code sample that a candidate wrote and an idea of how long it took them to work out they should automate it.

A text-book answer from an experienced techie is about 15-30 minutes and delivers a short piece of code that fetches the web-page, finds the sum with a regexp or similar, works out the answer with eval, creates the response and sends it back to us. However, people are much more creative than that.

One excellent answer was a single line of shell script, which did the whole thing in bash, but even more cleverly searched the process list for the command that had been typed in, added the escaping back in and then mailed itself to us – a one liner that did the puzzle, recreated its source code and emailed itself to us.

Another excellent answer was someone who guessed that our code had a 32 bit roll-over bug in, tried options until we generated an answer bigger than 2^32 and fixed the otherwise text-book code to implement the bug on our side.

The absolute worst answer we’ve ever seen was someone whose CV listed them as a professional programmer with five years experience. After two whole days of typing answers into the website they finally worked out that the problem had to be automated. After three days of development they wrote a vast piece of Java code that was able to download the page and find the problem but it was only able to work out the answer if there were only three numbers and they all had to be added together. Instead of improving the code for the general case they put it in a loop and repeatedly called the page until by sheer luck they got a page their code could answer. Creative genius but not in a good way.

On to the entrants

So this is a difficult challenge for school age children and teenagers. Most of the entries came from older children 16 and up, and it’s clear that it was difficult and they had to learn new things specifically to solve this. PHP and Python were the preferred languages – the most novice friendly of all the tools available. We were very torn as to who should win. After lots of deliberation our runner up is this php entry from Nils in Germany who was also the first to submit,


// That was fun. There should be more conetsts like this.
// Sorry for the incredibly hacked together code...
<?php

$challenge =
file_get_contents(‘http://sphinx.mythic-beasts.com/cgi-bin/job.pl’);

$task = preg_replace(‘/.*

Evaluate /is’, ”, $challenge);
$task = preg_replace(‘/ \, .*/is’, ”, $task);

$id = preg_replace(‘/.*name=\”id\” value\=\”/is’, ”, $challenge);
$id = preg_replace(‘/\”.*/is’, ”, $id);

function calc_string( $mathString ){
$cf_DoCalc = create_function(“”, “return (” . $mathString . “);” );

return $cf_DoCalc();
};

$ans = calc_string($task);

$url = ‘http://sphinx.mythic-beasts.com/cgi-bin/job.pl’;
$data = array(‘answer’ => $ans, ‘id’ => $id);

$options = array(
‘http’ => array(
‘header’ => “Content-type: application/x-www-form-urlencoded\r\n”,
‘method’ => ‘POST’,
‘content’ => http_build_query($data),
),
);

$context = stream_context_create($options);
$result = file_get_contents($url, false, $context);

var_dump($result);

?>

Things we particularly like are that all the comments and code and email are in English to make it easier for us, even though it’s the authors second language.

Our winner though goes to 13 year old Nick. From a pure technical standpoint his code isn’t as good as Nils’ entry above, but through the comments it tells the story of slowly working his way towards the solution and appropriately credits the help he received – both personal and online.


#Mythic Beasts - Win a Pi Zero
#Written by Nick Lockhart from Chepstow, Wales, aged 13 3/4
#with help from an old fossil (his dad)
#You will need LXML for Python and Requests

from lxml import html
import requests
debugmode = 1

#get the page and parse all

elements into a Python list.
#For this purpose we should only get one element.
page = requests.get(‘http://sphinx.mythic-beasts.com/cgi-bin/job.pl’)
tree = html.fromstring(page.content)
paragraphs = tree.xpath(‘//p/text()’)

#Split out the question.
#First take out everything after the sum (space included)
#And then remove everything before the sum (space again included.)
#And convert to a string. Oddly, after the second time, we have to
reference the second element as there is a blank string in question[0]
#Finally, evaluate it.

question = paragraphs[0].split(‘ ,’)
question = question[0].split(‘Evaluate ‘)
question = question[1]
answer = eval(question)

if (debugmode == 1):
print(“The question was: ” + question)
print(“The answer should be: ” + str(answer))

#There’s a hidden input labeled “id”, which seems to be randomly generated.
#This is probably to track who’s submitting.
#We will also need to extract this.
#I learnt this piece of magic with help from StackOverflow. Thanks,
Mathias Muller!

secretkey = tree.xpath(‘//input[@name=”id”]/@value’)[0]

#That’s all we need to POST. Let’s generate a payload, send it off and
extract the response.
#The server expects the answer to be a string, so we convert it to a string.

payload = {“answer”:str(answer),”id”:secretkey}

if (debugmode == 1):
print payload

response =
requests.post(“http://sphinx.mythic-beasts.com/cgi-bin/job.pl”,
data=payload)
responsetree = html.fromstring(response.content)
print(responsetree.xpath(‘//p/text()’))

Of course the final comment to everyone who entered is if you ever need any kind of hosting, domain name or similar send us an email and include your entry number for a freebie / upgrade /discount. Secondly if you seek summer work or gap year employment, we’d invite you to get in touch and we guarantee that we’ll read your CV and take your application seriously.

Rebuilding Software RAID 1 refused to boot

October 30th, 2015 by

Dear LazyWeb,

Yesterday we did a routine disk replacement on a machine with software RAID. It has two mirrored disks, sda and sdb with a RAID 1 partition with software RAID, /dev/md1 mirrored across /dev/sda3 and /dev/sdb3. We took the machine offline and replaced /dev/sda. In netboot recovery mode we set up the partition table on /dev/sda, then set the array off rebuilding as normal:

mdadm --manage /dev/md1 --add /dev/sda3

This expects to take around three hours to complete, so we told the machine too boot up normally and rebuild in the background while being operational. This failed – during bootup in the initrd, the kernel (Debian 3.16) was bringing up the array with /dev/sda3, but not /dev/sdb3, claiming it didn’t have enough disks to start the array and refusing to boot.

Within the initrd if I did:

mdadm --assemble /dev/md1 /dev/sda3 /dev/sdb3

the array refused to start claiming that it didn’t have sufficient disks to bring itself online, but if I did:

mdadm --assemble /dev/md1 /dev/sdb3
mdadm --manage /dev/md1 --add /dev/sda3

within the initrd it would bring up the array and start it rebuilding.

Our netboot recovery environment (same kernel) meanwhile correctly identifies both disks, and leaves the array rebuilding happily.

To solve it we ended up leaving the machine to rebuild in the network recovery mode until the array was fully redundant at which point the machine booted without issue. This wasn’t an issue – it’s a member of a cluster so downtime wasn’t a problem – but in general it’s supposed to work better than that.

It’s the first time we’ve ever seen this happen and we’re short on suggestions as to why – we’ve done hundreds of software RAID1 disk swaps before and never seen this issue.

Answers or suggestions in an email or tweet.

If you put your mind to it

October 21st, 2015 by



With today being Back To The Future day, it’s worth reflecting on two pieces of advice I received in the mid 1980s. The best piece of advice was definitely from the film:

‘If you put your mind to you, you can accomplish anything’.

the worst was my mother:

‘Stop playing on your Spectrum and go and do your piano practice’

I’m not certain this generalises, I think that largely your parents do give better advice than Hollywood script writers.

Professor Cathie Clarke, Ada Lovelace day

October 13th, 2015 by

Unless you really like maths, you’re probably better off just looking at the pictures.

Today is Ada Lovelace day, where we celebrate the achievements of women in the traditionally male dominated fields of Science, Technology, Engineering and Maths.

Mythic Beasts came about as a side project of a bunch of students, most of whom studied at Clare College Cambridge. As a Cambridge student you receive supervisions, hour long tutorials in sets of two or three. You also live in the college for three years and some fellows of the college also have rooms in the same accommodation. As luck would have it, our director Pete was partnered with one of our other founders, Richard for supervisions in Physics, and in the second year they were jointly supervised by Professor Cathie Clarke and it turned out that her college room was directly opposite Pete’s in Clare Old Court.

This led to a slightly unusual arrangement, rather than everyone trekking into the department for supervisions they decided to hold them in Pete’s room at 8am, usually accompanied by a bacon sandwich and strong black coffee before heading off to lectures. Cathie was a superb teacher, neatly covering dynamics, orbits and effortlessly showing why practically the whole of spaceflight involves pointing your rocket motor in obviously the wrong direction in order to get to where you want to go. She also, neatly answered other questions including electro-magnetism that had stumped pretty much the whole year in Clare and all the supervisors in that subject, despite having had about sixty seconds notice and only half a cup of coffee.

Pete’s room was on the top right hand corner of this photograph, the bacon cooking kitchen roughly above the passageway.

There was a particularly memorable supervision, where Richard overslept and arrived very late to Pete’s room, anxious he’d missed the supervision. On waking Pete up, they jointly discovered the note on the door from Cathie apologising that she’d overslept and the supervision would need to be rescheduled. A co-incidence for which all parties were grateful.

So whilst her impressive CV gives away the huge publication list, professorship and that she’s the course coordinator for astrophysics; in person we had the privilege of knowing that she is also a superb prize-winning teacher, gifted researcher and somehow on top of all that, a lovely human being who occasionally oversleeps just like the rest of us.

Happy Incorporation Day to Us

August 14th, 2015 by

Happy Incorporation Day to Us
Happy Incorporation Day to Us
Happy Incorporation Day to Mythic Beasts
Happy Incorporation Day to Us

Fifteen years ago today someone with a boring job processed the paperwork and Mythic Beasts Ltd sprang into existence as a legal entity.

We had existed informally for a bit longer than that, we had registered the mythic-beasts.com that April, and our shell server, sphinx, had been running for a while, although it wouldn’t be until early 2001 that we sent our first invoice.

As we all work on t’internet, it’s difficult to all meet in the same pub this Friday for a celebratory drink. That will have to wait until our next full company meetup in September. Slamming the bedroom door, staying in and watching Brazil seems a more apt way for a teenage company to celebrate its bureaucratic anniversary.

Women in Technology and avoiding ISP filters

June 29th, 2015 by

One of the Mythic Beasts, Rhosyn has written an article on filtering for trefor.net, a widely read blog on technology and networking.

The part we particularly like this this quote,

As a long standing customer of Mythic Beasts 
(shameless plug; outstanding service and support, 
so good that I switched companies recently to work 
for them)