Harry Jackson

qemu bridged networking

2012-03-04T07:38:45Z

My final /etc/networking/interfaces file looks like (this is for Debian)

auto lo eth0 tap0 br0

iface lo inet loopback

iface br0 inet dhcp
        bridge_ports eth0 tap0
        bridge_maxwait 0

iface eth0 inet manual

iface tap0 inet manual
        pre-up tunctl -b -u  -t tap0
        pre-up ifconfig tap0 up
        post-down tunctl -d tap0

I stole this from the following site joost.damad.be

Beware the username enttry above needs to be changed to your username... You will also need to install uml-utilities. Once I had this running I could start my image as follows:

qemu -net nic -net tap,ifname=tap0,script=no -hda debian.img

Mount You must specify the filesystem type

2012-03-02T23:00:32Z

I encountered this error while trying to mount an image created using qemu. The command from the docs says to run the following command to mount it on the loopback device.

mount -o loop,offset=32256 debian.img ./mntpoint

This is completely wrong because the data start is not 32kb into the image file. To figure out where it starts you need to use the following commands:

]$ fdisk -ul debian.img
you must set cylinders.
You can do this from the extra functions menu.

Disk debian.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00077ccb

     Device Boot      Start         End      Blocks   Id System
debian.img1   *        2048     5785599     2891776   83 Linux
Partition 1 does not end on cylinder boundary.
debian.img2         5787646     6141951      177153    5 Extended
Partition 2 does not end on cylinder boundary.
debian.img5         5787648     6141951      177152   82 Linux swap / Solaris

Once you have this output you can see that the data starts at sector 2048 and since sector size is 512 on my image I need to set the offset to 512*2048. So the final working command is:

mount -o loop,offset=$((512*2048)) -t ext3 ./debian.img ./mntpoint

and we now have a mounted image file.

Changing your keymap

2011-01-21T15:53:12Z

I recently had an issue where my keyboard when using synergy was inserting a double arrow instead of the usual greater than or less than sign also known as guillemotleft and guillemotright.

To fix this annoying bug I added

keycode 53 = x X greater greater greater greater
keycode 52 = z Z less less less less
keycode 24 = q Q at at at at

to a .Xmodmap in my home directory. If you are wondering how to find the keycodes etc you can use xev. To start it without restarting X use

xmodmap .Xmodmap

Google Bugs

2010-09-04T12:20:54Z

I am not sure what has been happening to Google recently but over the last few months it has got quite awkward to use. The first thing I noticed was the new fade in. For me while it's fading I'm unable to type anything into the search box. This is really annoying.

The other less annoying thing but annoying anyway is the fade itself, who on earth decided this was a good idea? Are they really that desperate for more searches that they will hide parts of their menus etc until you do something. I'm sure they've done some UED studies and concluded that it's better for the majority of people, personally I hate it.

The second thing I noticed today is that I lose control over the Firefox menu when I have a Google Window open on the home page. I was able to repeat this quite easily and when I close the Google tab I'd get control back. This is very very annoying.

It's getting more and more awkward to use Google and this spate of bugs is getting tiring. I appreciate Googles uncluttered page and speed but this is starting to take the piss.

As a Yahoo! employee these errors are of course good news for us. I've been an avid user of Google for years but I think it's high time I stopped using Google anyway and the recent spate of bugs has given me a good reason to try Bing/Yahoo to see how I get on with them. Hopefully within a few weeks my muscle memory for "goo" will change to "bin" or "yah".

Harry buys a new top

2010-07-22T22:15:12Z

This is my first attempt at a cartoon strip. I drew it on a whiteboard and then took a photo, that's why it's dark. I would be surprised if this has not been done before, it's a very obvious joke.

US British Bashing over Deep Horizon Disaster

2010-06-11T11:15:27Z

Disclosure: I'm a BP shareholder.

I've been watching the Oil leak since it started and I'm alarmed at what has happened; not because I'm a shareholder but because of the damage caused. BP needs to pay for the cleanup, I know this and it has cost me money in lost capital, BP knows this and so does half the world so why are we seeing ever increasing British bashing from the United States over this event.

For instance: Barack Obama is on record for using the old name of BP, “British Petroleum”, why would he do this? I'm sure his advisers know when the name changed and the implications of using it even if he doesn't. Fox news are quick to say things like “BP, formerly known as British Petroleum”, why are they saying that? BP is BP and has not been calling itself British Petroleum for some time. The level of bashing is getting out of hand and the papers in the UK are seeing this as an outright attack on the British. The news this morning was about three things, the World Cup, David Cameroon in Afghanistan and the US bashing the British over the oil slick.

The facts are that BP is a multinational company and the US own a large chunk of it:

The rig that exploded was owned by an American company and it was American people operating it. Bashing the British achieves nothing and will only harm relationships between the two states. The UK and the US have been staunch allies for years and we've spent many more billions together than what it will take to clean up the mess in the Gulf of Mexico. My fear is that some cretins will be allowed to deflate what is a solid relationship that will take much longer to repair that the oil slick. John Napier, CEO of Royal and Sun Alliance has put it much better than me in the following letter.

Barack Obama and the US public are right to ask BP to withhold the dividend until we know the extent of what has been done. I know the implications of this for the pension funds and other investors but hey, we bought BP shares, it's a bit late to complain now. We took the risk so we'll pay the price, that's how this stuff works and Barack Obama has a duty to make sure that BP can pay for the damage. However, the anti British rhetoric needs to stop because it achieves nothing and will only damage what is a fantastic relationship.

Oil sticks but grudges and ill feeling sticks much longer and will cost us all far more than the billions it takes to clean up the Gulf.

Gordon Browns Legacy

2010-05-11T20:24:53Z

Darren Foreman was kind enough to point out an article detailing Gordon Browns Legacy on the BBC today:

If you click on the image you will be able to see the full positive legacy that Gordon Brown has had on our country.

On a serious note Gordon was the Chancellor of the exchequer that allowed Tony Blair to basically spend spend spend his way to popularity. He sold the gold reserves for a quarter of what they where worth a few years later. But, to top it all off he has managed to increase total tax as a percentage of GDP from 39.3% in 1997 to 42.4% in 2006, going to a higher level than Germany. So the nation is now within 8% of actually working for the governement. How sad is that. I will soon be an employee of the state who happens to go to work for less than 50% of what I actually earn. No matter how you butter it, Big (read Natzi or Communist) government is just around the corner. When a government needs 42% of it's national output to fund what it does the nation being run by that governement is in serious trouble.

Superstition is Rife among developers

2010-05-11T20:18:10Z

I was reading John Stuart Mill's on Liberty and came across the following passage:

There is a class of persons (happily not quite so numerous as formerly) who think it enough if a person assents undoubtingly to what they think true, though he has no knowledge whatever of the grounds of the opinion, and could not make a tenable defense of it against the most superficial objections. Such persons, if they can once get their creed taught from authority, naturally think that no good, and some harm, comes of its being allowed to be questioned. Where their influence prevails, they make it nearly impossible for the received opinion to be rejected wisely and considerately, though it may still be rejected rashly and ignorantly; for to shut out discussion entirely is seldom possible, and when it once gets in, beliefs not grounded on conviction are apt to give way before the slightest semblance of an argument. Waving, however, this possibility—assuming that the true opinion abides in the mind, but abides as a prejudice, a belief independent of, and proof against, argument—this is not the way in which truth ought to be held by a rational being. This is not knowing the truth. Truth, thus held, is but one superstition the more, accidentally clinging to the words which enunciate a truth.

Have you ever heard Perl and PHP fans get stuck into each other, or Java vs C++, or Vim vs Emacs (there can be only one). It's crazy! Most of the noise is created by people who have no real understanding of the technology they are arguing against and some of them don't even understand the tech they are arguing for. Wikipedia has an entry on Editor Wars.

Basically Mr Mill is stating that if you are arguing against something with little real understanding about what that something is then your just another superstitious idiot.

Political Compass

2010-05-07T16:36:29Z

I am rather please with this: I took the Political Compass Test and I got the following result.

If you are wondering what the above means the following diagram will give you an idea of where I stand compared to some famous characters.

Patent Nonsense

2009-11-29T12:31:09Z

As an owner of shares in both Merck and Glaxosmithkline the
following is very depressing reading.

Patent Nonsense (Henry Mintzberg)

Surely any rewards system should be encouraging cures to diseases not relief of symptoms. The appendix of the article is very depressing, are they truly this corrupt. I wonder if any of these people actually go to prison for their actions. The Limited Company ancourages people to take risks they would not otherwise take in case of financial failure etc but surely when they start blurring the lines, especially when its peoples lives on the line, there must be some rule of law.

In 2008 Merck, Glaxo and Pfizer had a combined turnover of over $100 billion, a fine of a few million is like shooting an elephant with a pop gun, mild irritation but little cause for concern. The elephant continues on its merry way and soon forgets the sting on its ass. If you check out the first page of first page of Pfizers 2008 Annual Summary, they have a cute kid on the first page but do they give a damn about that kid or any other or is shareholder value the main driver. I know the company answer would of course being wrapped up in cotton wool and they would wax lyrical about how important people are but then why all the apparent corruption, the government fines. They cannot wash their hands of setting the wrong rewards system or crap managment, and I don’t mean crap management ie they got caught.

One of the reasons I bought shares in Merck was the story in Tom Collins Built to Last: Successful Habits of Visionary Companies about them helping with River Blindness, that’s a company I want to own a stake in. Don’t get me wrong their financials are also a factor but every company has a social responsibility and Merck’s actions in the River Blindess case was good evidence to me that they take that responsibility seriously.

Pfizer talk about putting trust back on the agenda in their 2008 report but then they all talk about Corporate Responsibility but is this just lip service ie we were naughty and we are cleaning up shop but really nothing changes. Do any of them realise that Corporate Responsibility is missing a word, “Social”, it should be Corporate Social Responsibility. I personally hope that the big pharmaceuticals stop talking about Corporate Responsibility and start living it. There are few other companies that can have a bigger impact on our total well being than the big pharmaceuticals and if we let them get away with this sort of nonsense we will continues to have countries with an average lifespan under 50 for years to come.

Glaxo 2008 Annual Report

Merck 2008 Annual Report

Pfizer 2008 Annual Review

Eclipse Cannot connect to keystore

2009-11-22T16:43:02Z

If you get the following error:

An error occurred during provisioning.
Cannot connect to keystore.
JKS

You need to check what version of java you're running. I'm running Debian and hat gij installed and this is no use for eclipse. I tried the following:

apt-get install openjdk-6-jdk
update-java-alternatives -s java-6-openjdk

but this failed miserably. I ended up downloading and installing a new java bundle from Sun and removing every debian package related to Java.

Mental Wanking and Premature Optimization

2009-08-30T21:57:20Z

Optimization appeals to us geeks. I am sure there is some psychological reason for this, If you happen to know what the reason is then drop me a line. I promise not about to witter on about The Fallacy of Premature Optimization either. Optimization is important but far too many of us get caught up in pointless arguments about performance. The following article deals specifically with the faster webserver, in particular serving static pages.

There's a ton of articles on Apache vs Apache2 vs lightttpd vs thttpd vs mongrel vs nginx vs litespeed vs whatever-httpd. The vast majority of these articles cater for people not adverse to a bit of mental wanking. These people have a perceived problem ie performance. They want to get an extra few percent from their machine. Off they go on their merry way Googling for a performance comparison chart that will show them some stats. These people are the unadulterated speed freaks of the computing world. A lot of them understand their... affliction, but quite a few don't.

In some organizations performance is critical ie Yahoo, Google, Wikipedia, livejournal, BBC, Dozens of Universities, Any bank, etc.... I am missing hundreds here. For some it's competitive advantage ie Google. For these organizations performance is talked about all the time. It's brought up in meetings, at the bar, over lunch, out jogging and in their dreams. It has a direct affect on the bottom line.

My point is this, most people online discussing the relative merits of Apache vs Apache2 vs lighttpd are not in this select group, most are running small websites.

Here are some idle thoughts that may help the more pragmatic developers out there.

A fairly common question asked is. "What hardware do we need to sustain "N" requests per second"? Assume a static page is 25KB. If we also assume that we have an eCPM of $1.00 (and this is a small amount) we can put "N" in perspective......

1 rps == 2,592,000 rpm == $2592 per month
10 rps == 25,920,000 rpm == $25,920 pm
50 == 129,600,000 rpm == $129,600 pm
100 == 259,200,000 rpm == $259,200 pm
500 == 1,296,000,000 rpm == $1.296 million per month

500 pages per second is nearly 1.3 Billion Pages per month. This is an awful lot of pages and $1.3 million dollars is certainly an awful lot of money. On hearing 500rps as a requirement a common reaction is to jump too Google and start looking for a suitable configuration. It would be far simpler and more enlightening to do a few calculations and a small test to see where we stand.

For instance:

500 * 25KB requests per second == (500*25*1024*8)b/ps == 104Mb/s

This is a serious requirement. A 100Mb dedicated line is not cheap and would be likely to set you back several thousand dollars per month but hey we are making $1.3 Million per month, who cares!

Now, if I was to go out and spend $2000 dollars on a server just how many pages could it serve. Lets assume I own the following machine:

Dell 2850
RAM: 2GB
model name: Intel(R) Xeon(TM) CPU 2.80GHz
cpu family: 15
6 10K SCSI disks (2 mirrored, 4 in raid 10)

Basically a decent spec 2005/6 Single Processor Dual Core machine with the OS disks on a raid 1 array and the web server serving pages from the raid 10 array.

So, is it possible for this single machine to serve 500rps? Yes! It could, if we had enough bandwidth! The following results were taken from a base install Debian machine. I did not tune apache2 in any way whatsoever. This was done on a 100Mb Ethernet network.

debian:~# ab -n 10000 -c 50 http://farty.com/
This is ApacheBench, Version 2.0.40-dev
Completed 1000 requests
.........
Finished 10000 requests

Server Software: Apache/2.2.3
Server Hostname: farty.com
Server Port: 80

Document Path: /
Document Length: 25000 bytes
Concurrency Level: 50
Time taken for tests: 21.877168 seconds
Complete requests: 10000
Failed requests: 0
Total transferred: 252929056 bytes
HTML transferred: 250243696 bytes
Requests per second: 457.10 [#/sec] (mean)
Time per request: 109.386 [ms] (mean)
Time per request: 2.188 [ms] (mean, across all concurrent requests)
Transfer rate: 11290.35 [Kbytes/sec] received

I know ab is not the best tool to be running benchmarks and that requesting a single file is different thatn random files etc but I am not trying to be precise.

So, a cheap machine can saturate a 100Mbit line. Yes, Easily. At no point during the tests did the server go over 0.5 load. I also ran a more long running test and the results were the same. It hardly broke a sweat and this is running an unmodified, untweaked pre-forking Apache2 server.

So whats the conclusion, is benchmarking Apache2 vs lighttpd pointless? I would say that 99% of the time, yes. If you ever have the problem were you need to be serving the amount of pages where the difference between Apache2 and lighttpd makes a big difference then you are likely able to afford more hardware or staff but I wouldn't be choosing lighttpd over Apache2 unless I really have to.

Heres a quote from a 20000 concurrent connection apache setup

... HEAnet's National Mirror Server for Ireland. Currently mirroring over 50,000 projects ..... It regularly sustains over 20,000 concurrent connections on a single Apache instance and has served as many as 27,000 with about 3.5 Terabytes of content per day. The front-end system is a Dell 2650, with 2 2.4 Ghz Xeon processors, 12Gb of memory and the usual 2 system disks and 15k RPM SCSI disks, running Debian GNU/Linux and Apache 2.x.

So the next time you hear someone discussing how fast their httpd server is at serving static content ask yourself if they are just jerking off or do they know what they are talking about.

Mental Masturbation

2009-07-19T11:31:17Z

My definition of Mental Wanking reads like a medical affliction.

Main Entry:: men·tal mas·tur·ba·tion

mental stimulation, especially of one's own mind commonly resulting in time wasting. Can be achieved by missing the point or an acute lack of realism. More prevalent in certain fields, critics ( in particular literature ), software engineers, tv buffs etc. Can occasionally be accompanied by mental fantasies, arrogance, bad temper and or delusions.

For those looking for individual definitions of the word I took the following from Websters.

Main Entry:: mas·tur·ba·tion

: erotic stimulation especially of one's own genital organs commonly resulting in orgasm and achieved by manual or other bodily contact exclusive of sexual intercourse, by instrumental manipulation, occasionally by sexual fantasies, or by various combinations of these agencies

And the following entry for Mental:

Main Entry:: ¹men·tal

1 a: of or relating to the mind; specifically : of or relating to the total emotional and intellectual response of an individual to external reality <mental health> b: of or relating to intellectual as contrasted with emotional activity

]]>

Main Entry:: men·tal mas·tur·ba·tion

Main Entry:: mas·tur·ba·tion

Main Entry:: ¹men·tal

Exim4 Unrouteable Address

2009-07-19T11:17:36Z

I have no idea when or why this started happening for me but I started getting Unrouteable address appearing for any external address.

I'm a huge fan of Debian but there are some things that really piss me off. One is the way they have completely screwed the exim4 configuration. Exim4, if you are not an administrator or mail guru is not the simplest thing in the world to configure, it's config file is fairly involved and you can do anything in it. Add DEBCONF variables to this and you have a complete nightmare configuration.I spent two days tracking this error down to the following:

DCconfig_internet=1

That was all I had to add to /etc/exim4/exim4.conf.template

Why this changed I have no idea. The setting I am using in /etc/exim4/update-exim4.conf.conf is

dc_eximconfig_configtype='internet'

I really cannot make head nor tail out of this at all. I sometimes wish I had started learning Postfix instead of Exim but part of me thinks that it's not Exim but rather the way it has been packaged up thats compicated.

Losing Weight

2009-04-18T15:22:15Z

I managed to get to 108 Kgs (17 Stone) by the 5th April. This was a total weight loss of 14 Kilos or for our imperial readers 31 lbs. The resting heart rate has not been going so well though, I stopped tracking it.