Planet GLLUG

davblog - Dave Cross: Week Notes 4 & 5

2012-02-05T08:40:54+00:00

One of the ideas behind writing these week notes was that it would force me to write at least one post a week. That doesn’t seem to have worked. So here’s a combined post for the last two weeks.

Health

It’s four weeks today since I broke my leg. The leg itself feels fine; it’s just the cast that’s bloody inconvenient. I get around the house pretty well, but I don’t get out much. Last weekend we took a taxi to Blah Blah Blah in Goldhawk Road to celebrate various birthdays. Other than a couple of trips to the hospital that was the first time I’d been out since it happened.

I was considering hobbling down to the pub quiz tonight. But the snow has probably put paid to that idea.

Speaking and Training

I was supposed to be in Romania at the end of last week, but we’ll be rescheduling that trip for later in the year.

I’ve been spending some time preparing for the public Perl courses I’m running at the end of the month. Still a few places left if you’re interested.

Writing

I didn’t write anything new (not even a blog post) but the final part of my three-part tutorial on Modern Perl was published in issue 155 of Linux Format which went on sale this week. I already have an agreement to write another series for them later in the year.

General Business Stuff

I finished moving all of my domains over to a shiny new server. And then I spent a week or so fixing all of the niggling little problems that I found. There still seems to be one outstanding problem with the Mailman configuration.

I bought a new laptop. It’s a Dell XPS 14z. I say bought – actually I’ve ordered and it’ll be delivered in the next ten days.

Buying it was a bit of a nightmare. I ordered it on Wednesday using the HSBC credit card that I got when I moved my company bank account. But unfortunately the credit limit wasn’t high enough (I’d forgotten about a few other things I’d put on t he card) and the transaction was declined.

But the transaction wasn’t declined as I was placing the order. No, it was declined at some point in the following twelve hours. So Dell cancelled my order. They didn’t contact me to find out if I wanted to try another credit card – they just cancelled the order. They didn’t even tell me that they had cancelled the order. I found out as I logged on to my account and checked the order status on Thursday morning.

I spoke to them and gave them the details of another credit card. But apparently they couldn’t just reactivate my existing order, they had to start again from scratch. And for some reason Dell’s web site seems to change from day to day so it took them 24 hours to be able to replicate my order at the same price. But finally on Friday morning I got an email confirming that the order had been placed. For £4 cheaper than the original order.

I can’t help thinking that Dell’s systems are a little overcomplicated.

Films

Watched a few films for the first time. Candyman was terrible. 127 Hours was grim, but gripping. The Troll Hunter was a lot of fun.

I’ve been investigating Netflix UK and LoveFilm Instant. I think that LoveFilm have a slight edge as their application is already installed on my Bluray player. For Netflix I’d need to use my Wii. I need to see if I can persuade LoveFilm to give me a free trial – as a returning member that doesn’t seem to be their default behaviour.

Richard WM Jones: rich

2012-02-04T12:52:04+00:00

Big theatre!

The code examples are in this git repository (git clone git://git.annexia.org/git/libguestfs-talks.git)

Tech Talk is here.

Richard WM Jones: rich

2012-01-31T20:00:25+00:00

Tech Talk — the superior technical presentation software — is back!

(Not surprisingly this coincides with me doing a presentation at FOSDEM this weekend …)

The new version has been rebuilt around WebKit (all the work for this was done by Dan Berrange). Mozilla were never really serious about “MozEmbed”, and in practice it crashed all the time. WebKit (or KHTML as we like to call it) is built from the ground up for embedding and it is rock solid, so it was just better to switch.

Also in this development version is support for VTE, which is a simpler way to display terminal output. Any shell script called *.term is rendered in a built-in VTE terminal emulator. You can still use *.sh for shell scripts that you want to run during your presentation (eg. for using your own terminal, or just running arbitrary programs).

Tech Talk PSE is available from git or in Fedora Rawhide.

Richard WM Jones: rich

2012-01-31T19:00:42+00:00

Here:

http://people.redhat.com/~rjones/libguestfs-RHEL-6.3-preview/

These are based on libguestfs ~~1.16.1~~ 1.16.2.

Richard WM Jones: rich

2012-01-31T18:13:02+00:00

FreeDOS 1.1 running in KVM with 4 MB (sic) of virtual RAM:

This is more than just a silly experiment. Being able to run very small VMs (and this is by far the smallest real VM I have been able to run) allows us to test the scalability of KVM to hundreds or thousands of guests using standard hardware.

It has revealed a couple of bugs in libguestfs too …

Richard WM Jones: rich

2012-01-26T09:52:55+00:00

In just over 1 week, FOSDEM 2012 is being held in Brussels. This flyer (PDF) is a handy guide to the Red Hat folk who will be giving talks there. (Thanks Máirín Duffy).

Richard WM Jones: rich

2012-01-25T10:40:24+00:00

In libguestfs 1.16 we added experimental GObject bindings and support for GObject Introspection. These are experimental because we may change them a little in future. They do allow you to access libguestfs from Javascript, specifically from gjs.

Here is an example program (fixed and updated):

const Guestfs = imports.gi.Guestfs;

function inspect (filename)
{
    var g = new Guestfs.Session ();

    //g.set_trace (true);

    var optargs = new Guestfs.AddDriveOpts ({readonly: true});
    g.add_drive_opts (filename, optargs);

    g.launch ();

    var roots = g.inspect_os ()
    if (roots.length == 0)
        printerr ("inspection: no operating systems found in", filename);
    else {
        for (var i = 0; i < roots.length; ++i) {
            inspect_root (g, roots[i]);
        }
    }
}

function inspect_root (g, root)
{
    print ("inspecting operating system root", root);

    print ("  product name:", g.inspect_get_product_name (root));
    print ("  version:",
           g.inspect_get_major_version (root),
           g.inspect_get_minor_version (root));
    //print ("  type:", g.inspect_get_type (root));
    print ("  distro:", g.inspect_get_distro (root));

    // Mount up the disks like guestfish -i
    var mps = g.inspect_get_mountpoints (root);
    var keys = [];
    for (var key in mps) { keys.push (key); }
    function compare (a, b) {
        if (a.length > b.length) return 1;
        else if (a.length == b.length) return 0;
        else return -1;
    }
    keys.sort (compare);

    for (var i = 0; i < keys.length; ++i) {
        g.mount_ro (mps[keys[i]], keys[i]);
    }

    // Get the list of applications.
    print ("  applications:");
    apps = g.inspect_list_applications (root);
    for (var i = 0; i < apps.length; ++i) {
        print ("    ", apps[i].app_name,
               apps[i].app_version, apps[i].app_release);
    }

    g.umount_all ();
}

if (ARGV.length != 1) {
    printerr ("Usage: gjs test.js disk.img");
} else {
    inspect (ARGV[0]);
}

Richard WM Jones: rich

2012-01-24T08:35:52+00:00

The release notes are here.

One highlight is GObject bindings, which makes the API available from Javascript. More on this topic coming soon.

Karanbir Singh: Communities and Questions

2012-01-23T10:56:00+00:00

I am often surprised by the sort of questions asked in the forums or on irc around open source projects - it just feels as if people are going out of their way to inflict pain and suffering upon themselves by trying to find the most awkward and most complicated way to do things. So how can we better help these people ? We dont need to save them or anything as drastic like that, its just a case of being able to show or explain that there might be a better way.

The first thing that I've started now doing, when asked a strange question is ask the person 'What are you really trying to achieve?'. You might be amazed how many times the answer has nothing to do with the question being asked. Try to establish what the end goal is, and in many cases its clear that the person has been lead astray by random posts on the internet, some of which are perfectly fine in their own context, but can be quite a kludge outside that context.

Establishing, clearly what the goal is before advice or opinion is thrown at people will always result in a better overall experience. And to the people spending their time in the irc channels, web forums and mailing lists helping others out : must respect. You guys are the ones making the idea of Communities and Open Source work.

- KB

davblog - Dave Cross: Week Notes 3

2012-01-22T08:49:15+00:00

Finally I actually managed to write a blog post that wasn’t week notes. That may well be my biggest achievement of the week.

Health

Still hobbling around in a cast and on crutches. Getting a bit better at it, but my upper body strength is still almost non-existent so I’m not going very far.

I went back to the hospital on Friday. On my previous visit it took about three hours. This time I did pretty much the same things and it took about half an hour. The doctor says everything seems to be going ok. They don’t want to see me for another four weeks. At that point they hope to remove the cast and replace it with a plastic boot.

Speaking and Training

Not much going on here. Still slowly building up to the courses I’ll be running at the end of February – which it now looks like I’ll be running with a plastic boot on, so there will probably be a fair bit of sitting down involved.

A couple of enquiries came in for training sessions later in the year. Looks like it could be a good year for my training business.

General Business Stuff

I host most of my domains on servers rented from 1 and 1. They’re not the best option by some distance, but they’re really cheap. At the end of last year I noticed that they had servers available running Centos 6. I rented a new server and have been slowly moving my domains over. This is a long and rather dull process. But I expect to be finished by next weekend.

Gigs

Anther gig that I couldn’t get to this week. This time it was Ed Sheeran at the Brixton Academy. Put the ticket on Gumtree and within hours I had a huge number of replies. Guess I set the price too low.

TV Highlights

Sherlock, of course. For the record, here’s my theory.

Moriarty had a Sherlock mask that he used when he kidnapped the children (which is why the young girl screamed when she saw Sherlock). Sherlock jumped into the back of the lorry that we saw, but at the same time threw off Moriarty’s body with the mask on. The cyclist that bumped into Watson also gave him a quick squirt of the H.O.U.N.D. gas so he saw what he feared most. Molly arranged to have the body collected and misindentified as Sherlock.

Of course, this is just a synthesis of many theories that have been going round on the web this week. And Stephen Moffat says there’s a clue that no-one has spotted.

Finished series two of Lost on DVD and made a start on series three. And we’ve started to watch Mad Men against from the start. Hope to watched it all before series five starts in April.

Hmm… doesn’t sound like I’ve achieved that much this week. But that’s probably an accurate reflection of how I feel.

davblog - Dave Cross: Nadine Dorries: Just Say No

2012-01-20T14:32:57+00:00

Today was the day that parliament had a rather long list of private members bills to debate. Originally there were sixty-four on the list. As this informative post from Kerry McCarthy tells us, they’d normally expect to get through about three of them. The MPs sponsoring the rest of the bills were pretty much wasting their time.

Number eight on the original list was Nadine Dorries bill to teach girls between 13 and 16 how to say no to sex. The Guardian’s headline was MPs to debate sexual abstinence lessons bill, which was slightly disingenuous as the chance of the debate reaching that far down the list was tiny.

But this morning, when the order of business for today in parliament was published Dorries bill was missing from the list. Everyone assumed that Dorries was responsible for this removal. As a spokeswoman for the Commons information office told the Guardian “No one would be able to remove a private members’ bill without the permission of a member”. The assumption seemed to be that Dorries had realised the futility of being so far down the list and had removed the bill. She wouldn’t have been the only one – the published list only contains forty-nine of the expected sixty-four bills.

At lunchtime, things got even more interesting. A new Twitter account called @NadineDorriesMP appeared with this tweet (in reply to a joke by John Prescott):

@johnprescott My bill has not ‘jumped off at Edge Hill’ if you care to read the order paper, it’s number eight on the list!!

Something about this timeline didn’t seem right to me. That tweet was posted at 12:47, which is almost two hours since I first saw the order of business without her bill. I assume the order of business was published some time earlier. The first hint I had that the bill had been withdrawn was this blog post by Kerry McCarthy which was published just after 10am.

On the basis that the real Nadine Dorries would have known by 12:47 that her bill was not on the order paper, I called the new Twitter account as a fake. But it seems I was wrong. People like Iain Dale confirmed that it really was her (and, yes, this is one of the few things I’d trust Iain Dale on).

All of which leaves us with a bit of a mystery. Either Dorries withdrew her bill or she didn’t. If she did then the first tweet on her new Twitter account is a complete lie. If she didn’t then we need to ask who did withdraw her bill – given that it’s only her who is supposed to be able to do that.

And even if someone else managed to withdraw her bill without her knowledge, something still doesn’t ring true. If she was expecting to debate her bill (no matter how tiny the chance) then surely she would have been hanging around in parliament all morning and I can’t believe that she didn’t see the order paper and notice her bill was missing. Or that one of her friends saw that it was missing and asked her what happened.

All in all I find it incredible that she could have got to 12:47 without knowing that her bill was not on the list. So how do you explain that tweet?

This is, I think, the third time that Dorries has joined Twitter. And with her first tweet she has already started people thinking that this time is going to be no different to the previous occasions. She will be ineptly trying to use it to promote her strange view of the world. And she will quickly make herself a laughing stock once more.

Update: At 16:37 this afternoon, @NadineDorriesMP tweeted the following:

Just to make it absolutely clear and leave no doubt whatsoever, my Bill was NOT withdrawn

Curiouser and curiouser. So, now we are left with two questions. 1/ Why wasn’t Dorries’ bill on the order paper? And 2/ At what point did she realise it wasn’t on the order paper?

Update 2: Welshracer may have got to the heart of the matter here. He points out what it says on the official parliamentary web page for Dorries’ bill.

The Bill was not printed and so was not moved for debate on 20 January 2012.

What do we make of this? One interpretation would be that Dorries didn’t withdraw the bill for debate, but that someone in her office forgot to get the bill printed so that it could be included in the debate.

But even in those circumstances you’d think that she’d get a phone call from the people who were planning the day’s business telling her what had (or hadn’t) happened. I still can’t believe that she didn’t know the bill wasn’t on the order paper when she sent her first tweet at quarter to one.

Update 3: Couple more pieces of information came in overnight.

Firstly, it seems that the new @NadineDorriesMP Twitter account was set up two weeks ago. It seems she resisted using it until goaded into it by John Prescott yesterday.

Secondly, the Independent managed to speak to Dorries about this confusion. She says:

The Bill is still live, but there was more chance of being struck by a meteor than getting it debated, so we told the Commons office not to bother printing a hard copy. What I didn’t realise was that if you don’t order it to be printed, it automatically comes off the agenda.

Of course I wouldn’t withdraw it … a lot of people had paid train fares to come and protest. It would have been churlish.

So we finally have the truth (or, at least, Dorries’ version of it). She knew it wouldn’t be debated so she decided not to have the bill printed. She didn’t know that would automatically remove it from the order paper. She didn’t withdraw the bill out of respect for the people who were coming to protest against it.

It’s also not clear to me in what sense the bill is still live. This was the final opportunity to debate private members bills before the end of this parliamentary session. Any unfinished business from this parliamentary session doesn’t get passed on to the next one, so anything that wasn’t approved is, as far as I can see, effectively dead.

You couldn’t make this up!

Richard WM Jones: rich

2012-01-19T14:56:38+00:00

I answered a question on a mailing list about live migration versus copying guests between different versions of KVM on RHEL. The complainant observed that you can’t live migrate from RHEL 6.2 to RHEL 6.1. But you can shut down a guest, copy it from RHEL 6.2 to 6.1, and boot it.

Why is there this difference? It comes down to how live migration is implemented.

Live migration is completely different from shutting down and copying a guest. During live migration we must send the complete state of system RAM, virtual CPUs, and all virtual devices, over to the remote side. In qemu this is done by sending “VMState” structures over the wire, one struct for each device that the guest is using. These structures are mostly a memory dump, but so that you don’t need byte-for-byte compatible versions of qemu when live migrating, each struct is preceded by a version ID.

The receiving qemu checks that it can handle that version of the struct. In some (but not all) cases, qemu knows how to “upgrade”, say, a version 1 struct into a version 2 struct. Downgrades are never possible, and some upgrades are also rejected (eg. if version 2 is a complete rewrite over version 1, then it’s possible for a device to refuse to deal with version 1 structs at all).

Downgrades are not possible, and that’s the basic reason why live migration doesn’t work from a newer to an older version of qemu.

Why does copying work? When a VM is shut down, there is no RAM, vCPU or device state. All the state that remains is the contents of the hard disk. If the hard disk is booted on an older qemu, then the kernel, during boot, will test the available CPUs, devices, etc and adjust itself, exactly the same as if you took a physical hard disk and transplanted it between real machines.

Indirectly related to all this is the qemu machine type. If you created guests on RHEL 6.0, then you may notice the libvirt XML contains:

<type arch='x86_64' machine='rhel6.0.0'>hvm</type>

This machine type stays with the guest even when you update the host.

The machine type controls what devices and PCI slots we present to the guest at boot, and it’s mainly there so that Windows doesn’t try to reactivate itself when you upgrade your host. The newer qemu presents the old devices and PCI assignments, so Windows doesn’t “notice” the updated hypervisor.

For Linux guests this is usually not a problem you have to worry about and you can go ahead and change the machine type at will.

Richard WM Jones: rich

2012-01-19T14:28:16+00:00

This was unexpected:

Write something to a partition device (eg. /dev/vda1) and immediately call blockdev --rereadpt /dev/vda to re-read the partition table of the whole device. Sometimes (about 50% for me) the blockdev command fails with:

blockdev: BLKRRPART: Device or resource busy

Nothing else is using /dev/vda, nothing from it was mounted, and the error was intermittent which indicates a race condition.

Why this happens:

udev has a rule that runs blkid -o udev -p /dev/vda1. It does this every time you close a block device so that blkid can rescan the content of the device.

The act of blkid running very briefly behind our backs causes the device to be open during the blockdev operation, causing it to fail.

Adding udevadm settle between the close and the blockdev fixed the problem for us, although this command is also inherently racy (what happens if it runs before the kernel has sent a message to udev?)

Richard WM Jones: rich

2012-01-18T18:34:44+00:00

There is a new tool in libguestfs ≥ 1.15.17: virt-format lets you erase disks and make blank disks.

Usage is quite simple:

$ virt-format -a disk.img

(Note that erases any data on disk.img!)

This works for any format of disk, eg. qcow2, or you can run it on host partitions, LVs, USB storage etc. By default it just creates a partition, but using other options you can make empty filesystems and logical volumes.

This is a simple tool that doesn’t cover everything you might want to do. For more complex requirements, see virt-make-fs or guestfish.

davblog - Dave Cross: Week Notes 2

2012-01-15T11:32:06+00:00

When I said I was going to experiment with week notes on this blog, I didn’t intend that the blog would only consist of week notes. But as we’ll see below, other things have been taking my attention this week and I haven’t felt much like blogging. Hopefully normal service will resume very soon.

Health

This is the big one. A few hours after posting my last week notes I slipped down a small flight of stairs in my house and fell badly. Something went ping in my ankle and it hurt like hell. I shuffled onto my bed where I lay for twenty minutes or so before deciding it wasn’t getting any better and I should probably take myself to A&E.

Four or five hours later I left A&E with a diagnosis of a spiral fracture in my fibula, a temporary cast, crutches and an appointment to go to the fracture clinic on Friday.

I spent the week hobbling about the house on crutches and went back to the hospital on Friday. They replaced the temporary cast with a more permanent one in sexy black fibreglass which I’ll be sporting for the next five weeks or so. They also took another x-ray and confirmed that although there’s definitely a fracture, everything is still in the right place so there’s no need for surgery, pins of any of that nonsense.

Going back to see them again next Friday.

Speaking and Training

The downside of having your leg in a cast is the doctors don’t like you flying – the pressure in the cabin can lead to blood clots. So I’ve had to postpone the trip to Romania. It hasn’t been rescheduled yet, but I hope to get there later in the year.

Counting the weeks, it looks like the cast will be coming off just before my other currently scheduled classes – the public courses for FlossUK and O’Reilly at the end of February. If I don’t heal on schedule then I expect I’ll be giving the classes sitting down.

Incidentally, those lovely people at O’Reilly have arranged to give away one free ticket to each of the two courses. Full details on how to enter are in an advert in the new issue of Linux Format. There are also runners-up prizes of copies of the new camel book.

Writing

Having spent the week sitting around at home, you’d think I would have had time to do plenty of writing. But, to be honest, I just haven’t been in the mood. The most I can report here is that I’ve got an agreement write four more articles for Linux Format over the next few months. I hope to finish the first of these (which isn’t about Perl!) today.

Reading

I have at least managed some reading. I’ve picked up Bruce Tate’s Seven Languages in Seven Weeks which I started reading in August but never quite got to the end of. And I’ve started reading Build Your Own Wicked WordPress Themes because I can see myself getting deeper and deeper into WordPress this year.

Gigs

I had a ticket to see Ani DiFranco at the Union Chapel on Tuesday. But my limited mobility mean that I couldn’t get there. I sold my ticket to the very lovely (and talented) Kal Lavelle. Luckily there are lots of videos of the gig on YouTube so I’ve been able to at least see some of the show.

Film

I had a ticket to see The Iron Lady last Sunday afternoon, but I was in A&E at the time. Later in the week I finally got to see In Bruges, which I’ve been planning to watch for ages. Oh, and one morning when I was sitting on the sofa feeling a bit sorry for myself I watched Sixteen Candles. Can’t beat a bit of Molly Ringwald to cheer youself up.

Sherlock was another ninety minutes of delight, of course. And I was pleased to see that The Good Wife returned to More 4. VirginMedia have half of the fourth series of Big Bang Theory on their video on demand service, so I’ve worked through that and am waiting for them to add the rest. We’re working our way through a DVD boxset of Lost – we’re currently close to the end of series two.

But the big surprise has been American Horror Story. We’ve watched all of the first series. Sure, it’s a clichéd in places, but part of the fun is spotting all the references to horror films. We love it.

Richard WM Jones: rich

2012-01-12T11:17:55+00:00

… are here.

Karanbir Singh: Fosdem and Visas

2012-01-09T22:04:00+00:00

Looks like I will need to get a Visa again to visit Belgium for Fosdem 2012. This is starting to get a bit irritating now, six times I've been to Fosdem and every time they have asked me to come in for an interview before they give me a visa; once again ? Surely by now it should be possible to get onto the visa-by-post process.

- KB

davblog - Dave Cross: Week Notes

2012-01-08T08:29:33+00:00

A new experiment on the blog this year. I’m planning to write a weekly report on what I’ve been doing. No idea how useful or interesting it will be or how long I’ll feel like keeping it going. So here’s what I did this week.

Speaking and Training

Didn’t give any talks this week, but there are a couple of things in the pipeline. I’m running four days of public Perl training courses in London at the end of next month and I’m starting to get into the marketing for that. O’Reilly have offered two free places on these courses as prizes for a competition that has been advertised in Linux Format.

As part of my marketing campaign I’ve been working on a new web site about my training business. Currently I’m working on the content. The look will come later.

Probably the most exciting thing to happen in this area is that I’ve been invited to give a talk about Perl in Transylvania. I’ve been doing some work with some Romanian Perl programmers and they’ve asked me to go over and talk to their new Perl Mongers group in Cluj. I’m going over for a couple of days at the start of February.

Programming

Over the last few months, Linux Format have been publishing a series of articles I’ve written about Modern Perl. The third and final article in the series will be published next month. The articles are about writing a web application to track a reading list. This was to replace a bodged together system or Perl programs that I’ve been using to track my reading for the last few years. This week I finally put the replacement system live at books.dave.org.uk. If you’re interested, the code is on GitHub. At some point I should probably write an article about it on my Perl blog.

General Business Stuff

About a month ago I realised that I was tired of dealing with Nat West for my business banking. It seemed that they made everything far more complex than it needed to be. I asked for advice on Twitter and most people seemed to recommend using HSBC instead. So I applied for an account with them through their web site.

Well, it wasn’t anywhere near as easy as it could have been, but last Saturday I finally opened my new business account. With a new bank account and a new accountant a few months ago it really feels like the business has started a new era.

People ask why I carried on with the HSBC application when it was all so painful. That’s because I still think they’re more efficient than Nat West were. It crystallised for me when I was thinking about the computer systems that they use. In recent months I’ve spent far too much time in Nat West branches watching the screen as an assistant tries to sort out a problem. Their internal systems are all running on what seems to be CICS-based software from the 1980s. When I was watching the chap opening my account in HSBC last weekend it looked like they were running an old version of Windows from the 1990s.

So HSBC’s software seems to be about a decade more up to date than Nat West’s. But still twenty years behind the rest of the world. Surely banking doesn’t need to be so tortuous?

House Stuff

I spent a lot of last week finishing a decluttering exercise that I started after Christmas. I’ve shredded a huge mountain of old paperwork and for the first time ever I have every piece of paper in my study filed in the right place.

Our back garden backs onto a railway embankment and there are a lot of trees there. So we get a lot of leaves covering the back garden. Yesterday I went out and swept up several months worth of fallen leaves. One of the tree has nasty small leaves which get through the grills over drains and block them. So I lifted a lot of drain covers and pulled out a lot of muddy leaves. It wasn’t fun.

TV Highlights

I’ve been watching a lot of TV. The new series of Sherlock was an obvious highlight. But I’m also enjoying the Sky version of Treasure Island and the BBC’s Public Enemies. One thing I didn’t enjoy was Eternal Law. Despite being written by the same people as Life on Mars, the premise of lawyer angels proved to be just as silly as it sounds.

Health

The scales just told me that I’m almost three pounds lighter than I was a week ago.

Richard WM Jones: rich

2012-01-02T21:52:01+00:00

Over the holidays I started a new project called “wrappi”.

The name is a play on “wrapper” and “API”. And a play on what has been discussed for a very long time inside Red Hat — an API for everything that Red Hat Enterprise Linux does. A “rh-api”, if you will.

Wrappi aims to wrap up everything you can do with a Linux box:

many POSIX functions for creating files, mkdir, reading and writing files, etc
many command line tools, mkfs, fsck, parted, pvcreate, cp etc
block devices, firewall rules, services, processes etc
reboot, shutdown
a way to read and modify all configuration files
access to all the performance stats

We take all of that and present it back to you as an API:

available from C and a dozen other programming languages
available in a more powerful shell than bash, something like Microsoft’s PowerShell
accessible remotely over ssh, HTTP, XML-RPC, dbus, and a dozen other protocols

The aim is that from a PowerShell-like interface (or your own program) you could control and maintain 100s of Linux machines remotely. Like puppet/chef, but at a lower level.

Here is what a C program using the API might look like.

So this is ambitious.

An API that did all of the above might run to 10,000 different calls. To make this feasible to maintain and implement, we have to be able to generate the code for just about everything.

Each API call starts with a description. Because we need to write this description for 10,000 calls, it’s best to keep this short. In the best case, just a single line would be required, but in some cases it’ll be more complicated:

entry_point void mkdir (pathname path, fileperm perm)

system_object block_device
  dir_list "/sys/block/[hsv]d[a-z]*"

entry_point
struct timeval gettimeofday ()
<<
  int r;
  struct timeval tv;

  r = gettimeofday (&tv, NULL);
  if (r == -1) {
    set_error_errno ("gettimeofday");
    return NULL;
  }
  ret->tv_sec = tv.tv_sec;
  ret->tv_usec = tv.tv_usec;
  return ret;
>>
includes ["sys/time.h"]

From that metadata we can generate automatically everything we need, all the language bindings, all the remote access code, the implementation.

When a new shiny-thing comes along (“JSON-powered Enterprise GObject”) we can simply add a new generator backend, and we’ll support the whole API through that.

If you’ve followed my blog, you’ll know that this looks a lot like the libguestfs generator, and in many ways this is the generator done right.

There’s lots of code in the git repo. If you want to find out more, follow the blog, or ask questions below!

davblog - Dave Cross: Review of 2011: Favourite Posts

2012-01-02T06:37:33+00:00

And here’s the second post in my review of 2011. This is a list of my favourite posts from the year. In 2010 I said it was harder to choose posts from that year as I had blogged less than in previous years. Well, I actually blogged even less in 2011 so it was even harder this year.

As usual I’ve tried to pick one post from each month, but because of the scarcity of posts I’ve had to bend the rules at times. Usually I don’t include posts that have already been mentioned in the list of most popular posts, but that has proved impossible this year so there is a small amount of repetition.

Boothill Foot-Tappers. The Boothill Foot-Tappers were one of my favourite band from twenty-five years ago. I thought I’d never see them play again, so it was great that they got together for a one-off reunion gig.
Leaving LoveFilm. I cancelled my LoveFilm subscription early in the year. This post explained why.
Genealogy Primer. A friend on Facebook asked for help starting his family tree. I wrote a quick braindump in reply. Later I thought that other people might find it useful so I turned it into a blog post.
Daily Mail on Google and Adele. One of the most ridiculous articles ever from the Daily Mail, debunked easily with the aid of Google.
Watching the Press – Notes. In May I gave a talk at Opentech about the nonsense published by the British tabloid press and how a group of us try to bring this to the public’s attention by blogging about it. This post contains the notes from that talk.
Free Web Advice: TalkTalk. TalkTalk really annoyed me by phoning me despite my phone number being registered with the TPS. They then annoyed me even more by making it next to impossible to discuss the matter with them. This post enumerated the many ways that their web site made this hard. I’m slightly ashamed to admit that I finally just gave up.
Reading the News. A post about how I read the news these days and why a Kindle subscription to a newspaper doesn’t really fit into my life.
Hating Gnome 3. My favourite Linux distribution switched its default interface to Gnome 3. This made me very sad.
The Birth of a Meme. Some people writing in the Daily Mail claimed that the BBC had banned the use of the terms BC and AD and had forced broadcasters into using BCE and CE instead. This was completely untrue but that didn’t stop it repeated all over the media. Even now I suspect that a large proportion of the public think that it’s true.
Dorries on Humanism. Nadine Dorries was nominated for the New Humanist’s annual Bad Faith Award. She responded with a trademark closely-argued explanation of why Humanism is an extreme belief that no-one should admit to holding. Her reasoning obviously impressed New Humanist’s readers as she went on to win by a huge majority.
Winterval. More nonsense from the Daily Mail. But this time they’re admitting that it’s nonsense. When they started to publish a “Corrections and Clarifications” column I don’t think that anyone would have predicted that it would be used to undermine their core beliefs so quickly.
The War on Christmas Cards. Another Mail article to close with. They claimed that there was an atheist plot to keep religious Christmas cards out of the shops. They also complained about the increased numbers of “obscene” cards – whilst, in another article, praising the work of Donald Gill from a hundred years ago.

It was only while writing this review that I noticed that four of these twelve articles are about the Daily Mail. Looks like the blog might, finally, be developing a theme.

Last year was my lightest year for blogging. In fact every year has seen fewer post since I joined Twitter. Tweets are, of course, far less effort than blog posts. But nevertheless I shall, once again, endeavour to blog more often in 2012.

Thanks for reading in 2011.

davblog - Dave Cross: Review of 2011: Most Popular Posts

2012-01-01T08:56:14+00:00

As I’ve done for the last few years I’m going to spend a couple of days looking back at the year on this blog. Firstly, here’s a list of the ten most popular posts on the blog this year.

Winterval. No surprise here. Because I monitor the Mail’s Corrections and Clarifications column, I was one of the first people to see that they had finally admitted that Winterval wasn’t the atheist/muslim plot they’d always claimed it was.
Leaving LoveFilm. This has been a bit of a slow-burner. It’s only so high because it was published early in the year. I explained why LoveFilm’s rental model no longer fitted in with the way I want to watch films. Still waiting for them to offer streaming-only subscriptions.
Hitchen’s Last Laugh. A look at the nonsense that took place on Twitter a couple of weeks ago following the sad death of Christopher Hitchens.
MPs and Facts. Not much politics on the list this year. This is a reaction to Nadine Dorries’ appearance on Any Questions where she (unsurprisingly) talked nonsense about drugs.
Chuggers. I’d been meaning to write something like this for at least a couple of years. Surely everyone hates being stopped by chuggers, don’t they? This was probably the longest comment thread of the year.
Daily Mail on Google and Adele. I’m rather pleased with this one. The mail published some nonsense about how Google is deliberately encouraging piracy to bring down the British music industry. It didn’t take very much research to disprove their claims.
Independent URLs. I’d forgotten this one. Back in April someone discovered a tiny flaw in the way the Independent’s web site automatically cleaned up URLs. Much hilarity ensued. This post explained what was really going on.
Alternative Vote. An attempt to explode some of the myths used by the No campaign to stop people voting for the alternative vote. It apparently didn’t work.
Message to ADT. Surprised to find this on the list to be honest. The ADT web site annoyed me so I wrote a post about it. Ten days later I got a reply from someone at ADT saying that my suggestions had been implemented. Which was nice.
MPs on Twitter. A review of the number of MPs on Twitter and how it had changed over time. I even drew a nice graph. I need to revisit this project.

So that’s what you’ve been reading on the blog this year. At some point in the next couple of days, I’ll post a list of my favourite posts.

davblog - Dave Cross: 2011 in Gigs

2011-12-29T09:51:47+00:00

One of my pet hates is all that “review of the year” stuff that appears before the year is over. But I’m not planning to go to any gigs in the next three days, so I feel justified in reviewing the gigs I’ve seen this year before the end of the year.

According to Songkick I’ve seen exactly fifty gigs this year. That’s over twice as many as I saw in 2010.

There are two artists that I saw four times – Stealing Sheep and Martin Carthy, but as Carthy was a guest star on two of those appearances, I guess that Stealing Sheep are the band I saw most. Not bad for an act I first saw in August. There were two acts that I saw three times – Antonio Lulić and Ed Sheeran. I also saw Amanda Palmer twice – and as they were on a Friday and the following Monday, I expect she was the artist I saw with the shortest gap between performances.

I’ve seen gigs in rooms above pubs and one gig at Wembley Arena. Judging by my attendance at venues, my favourites are the Union Chapel and the Barbican Centre.

So what did I like? Actually let’s start with what I didn’t like. I walked out of two gigs halfway through the main act. I went to see Other Lives purely because Hannah Peel was supporting. She was great, as always, but they were terrible. Later in the year I decided to go to see Emmy the Great purely because lots of people I like say how she is. Unfortunately I chose her Christmas party gig with Tim Wheeler and it was horrible. I left after half an hour. In both cases I took a chance on liking an act and in both cases I was wrong. I suspect I’ll be doing a lot less of that next year.

There were a lot of nostalgic gigs on the list this year. Eddi Reader at the Union Chapel was great. Ian McCulloch a week later at the same venue was less great. I think I would have been better off seeing Echo and the Bunnymen instead. Later in the year I saw two great nostalgic gigs at the Bush Hall – Roddy Frame and Michelle Shocked.

I also saw some stuff from even earlier than that. Van der Graaf Generator were really good, but I didn’t really enjoy Yes that much. I even saw Hawkwind for the first time since 1982.

I’ve trying to work out what my favourite gigs were. But there such a wide range of stuff that it’s hard to compare them. Here, in purely chronological order, are ten highlights of my live music year.

Antonio Lulić, Jesper Ejrup, Trevor John, and Tess and Dibs at the Bedford. Didn’t see enough stuff at my local pub this year, but this was a brilliant night. All of the acts were top quality but the mad Danes in Jesper Ejrup’s band were particularly brilliant.
The Boothill Foot-tappers at the 100 Club. This was pure nostalgia. I’ve written before about what this band meant to me. It was great to have the chance to see them again.
Billy Bragg at the Queen Elizabeth Hall. Hadn’t seen Bragg play for far too long. This gig proved he still has it.
Rain Dogs Revisited at the Barbican. Various artists playing songs from Tom Wait’s album “Rain Dogs”. I love these nights at the Barbican. There’s always someone fabulous playing that I’ve never heard of. On this occasion, that was St Vincent. As soon as I got home I bought both of her albums.
Pulp at Brixton Academy. I never saw Pulp in the 90s and I was seriously considering going to the Wired festival to see them in the summer. Glad I didn’t though as this gig in Brixton was very nearly perfect.
Amanda Palmer at Heaven. An Amanda Palmer gig is always a treat, and this was no exception. Certainly one of the maddest nights I’ve had this year. Saw her again (at the British Library of all places) three days later for a rather more subdued (but equally brilliant) night.
Kal Lavelle, Ryan Keen, and Antonio Lulić at the Bedford. Proof (I hope) that I don’t just enjoy seeing old farts play. Kal, Antonio and Ryan are part of an informal group of incredible singer-songwriters who are constantly playing around London (and further afield). At the time of this gig all three of them had recently supported Ed Sheeran at various gigs.
Roy Harper at the Royal Festival Hall. Someone else I should have seen years ago but never got round to. Plenty of interesting guest stars – including Jimmy Page.
Zappa Plays Zappa at the Barbican. Sadly, I’ll never get to see Frank Zappa play, but this is about as close as you can get. Dweezil Zappa plays note-perfect renditions of his father’s music. And at some points they had film of Frank playing which the live band jammed along to.
Stealing Sheep at the Old Blue Last. Must include Stealing Sheep on the list. This was probably the best I saw them play.

All in all it’s been a good year for live music. I’ve ticked off a few more old favourites that I hadn’t previously got round to seeing and I’ve seen a lot of new and interesting bands. I’m already booking tickets for next year and hopefully it’ll be just as interesting as this year was.

What did you see that you really enjoyed this year? Did I miss any absolutely essential shows? What’s going to be great next year?

Richard WM Jones: rich

2011-12-27T16:49:24+00:00

It was out a couple of weeks ago. Previously …

davblog - Dave Cross: The War on Christmas Cards

2011-12-22T21:17:02+00:00

The Mail might have finally been forced to admit that Winterval wasn’t the the pagan plot they’ve always claimed it was, but that doesn’t mean they’ll stop publishing spurious “War on Christmas” stories whenever the fancy takes them. Today they turned their attention to Christmas cards and really didn’t like what they saw.

The headline was “Stores ‘ashamed’ to sell religious cards… but obscene ones litter the High Street“. The Mail have apparently had staff out on the high streets counting the number of religious Christmas cards on sale in various shops. They calculate that just half a percent of the cards for sale had a religious theme. They then took this information to “Christian leaders” for comment. This included well-known Christian nutter Stephen Green whose comments were every bit as intelligent and nuanced as we have come to expect.

I can’t believe this is being led by consumer demand.

I believe there is anti-Christian prejudice in the buying departments involved.

There’s too much of this multicultural indoctrination and too much of an idea that if they put out Christian cards they will alienate or discriminate against or offend other faiths.

There’s a kind of militant atheism and nasty secularism at work in this country which is completely opposed to Christianity.

He’s totally wrong, of course. This is completely lead by consumer demand. Shop owners aren’t stupid. If there was a demand for religious Christmas cards then they would meet it. If there aren’t many religious cards for sale it means that no-one is asking for them. Christianity is in decline in this country. That’s a simple fact that Christians (and the Daily Mail) are just going to have to accept.

But a lot of that article seemed a little familiar. And a little digging revealed Stores airbrush Christ out of Christmas cards from December 2010. Same writer, same survey, almost identical quotes from Stephen Green and other “Christian leaders”. I hope Andrew Levy wasn’t paid the full rate for both articles. Oh, and there’s another article on the same subject from 2006.

Something that was new to this year’s version of the article was the comparison to other Christmas cards that were on sale. Not only are religious cards in short supply, but the Mail was very distressed to find the shelves apparently packed with obscene cards with messages like “Merry Fucking Christmas”. With it’s useful sensitivity the Mail wanted to make sure that its readers knew exactly how disgusting these cards were so it listed plenty of examples – making liberal use of asterixes in certain words, but leaving us in no doubt what the real words were.

However, the Mail railing against these obscene cards seemed more that usually ridiculous when another article appeared on their web site later in the day. This new article was a celebration of the “bawdy” Christmas cards designed by Donald Gill at the start of the twentieth century. Surely the difference between “bawdy” and “obscene” is just the passage of time. I wonder if it’s worth searching the British Newspaper Archive for Mail stories from a hundred years ago complaining about Gill’s work?

Richard WM Jones: rich

2011-12-22T20:18:55+00:00

Paolo Bonzini discovered that you can issue SCSI ioctls to virtio devices which are passed down to the host.

The very unfortunate part about this is it easily allows guests to read and write parts of host devices that they are not supposed to. For example, if a guest was confined to host device /dev/sda3, it could read or write other partitions or the boot sector on /dev/sda.

In your guest, try this command which reads the host boot sector:

sg_dd if=/dev/vda blk_sgio=1 bs=512 count=1 of=output

Swap the if and of arguments around to exploit the host.

Here’s Paolo’s write-up on LKML.

Here is the libguestfs mitigation patch. The libvirt mitigation patch.

Richard WM Jones: rich

2011-12-21T18:18:29+00:00

Not being a regular library causes no end of constant build problems.

Like this crap because we did “gettextize” without doing “autoconf” (or vice versa):

make[2]: Entering directory `/builddir/build/BUILD/libguestfs-1.14.7/po'
*** error: gettext infrastructure mismatch: using a Makefile.in.in from gettext version 0.17 but the autoconf macros are from gettext version 0.18

I just don’t get why gettext can’t be a regular, ordinary, plain library so we don’t have to constantly suffer from this sort of thing. There is surely no other library that needs to rewrite your entire build system.

Richard WM Jones: rich

2011-12-20T13:28:53+00:00

You want to know if Android or iPhone is going to “win” in the end? It’s obviously going to be Android, because it’s the new Windows.

Exhibit (a): My Google Nexus S phone: requires rebooting every 3 days otherwise it just stops being able to receive/send calls and/or texts. Data over 3g still works during these outages.

Exhibit (b): My new Samsung Galaxy tab, a Christmas present of sorts from Red Hat: Fresh out of the box(!), this cannot connect to my wifi (absolutely everything else can connect fine to this wifi). Support forums are full of people reporting the same thing, and everyone suggesting you reboot/reinstall/press some magic key sequence/etc. Where have I heard that story before?

davblog - Dave Cross: Did Twitter Censor #GodIsNotGreat?

2011-12-18T10:19:49+00:00

[Executive summary: Betteridge's Law (probably) applies]

The Twitter furore over the #GodIsNotGreat hash tag has pretty much died down now, but there’s one branch of the debate that is still getting comments and retweets. Here’s an example from johnwilander.

#GodIsNotGreat pulled from trends because christians protest. But #ReasonsToBeatYourGirlfriend was allowed. Stay classy, @Twitter.

As I mentioned a couple of days ago, the hashtag vanished from the list of global trending topics on Friday morning. And this conspiracy theory leapt up almost immediately. As far as I can see, none of the people repeating this claim have any evidence to back it up – which is more than somewhat ironic given Hitchens’ evidence-driven view of the world.

The argument seems to go like this: At one point the hashtag was trending. Then Christians got upset and starting making death threats aimed at the people who started the trend. Soon after that, the hashtag was no longer trending. Therefore Twitter must have given in to Christian bullying and censored the hashtag.

Whilst it all sounds frighteningly possible, I hope I don’t have to spell out the flaws in the logic. If you can’t work it out for yourself then I recommend the Wikipedia article on Correlation does not imply Causation.

I could be wrong here. There might be some irrefutable piece of evidence proving conclusively that Twitter deliberately censored the hashtag. If there is, then I haven’t seen it and I’d be grateful to anyone who could bring it to my attention.

There is, however, some evidence that Twitter didn’t censor the hashtag. On Friday morning, as the debate still raging, a Facebook friend in Canada pointed out that it was still trending there. In the middle of the afternoon someone pointed out that it was still trending in San Francisco. So if Twitter were censoring it, they weren’t doing a very good job. There’s even someone who apparently works for Twitter saying that they didn’t do it.

Of course, none of this is conclusive evidence that Twitter didn’t censor the hashtag. But balancing some evidence for non-censorship against absolutely no evidence at all for the censorship I know which side I come out on.

All of which leaves us searching for an explanation for the sudden disappearance. And, to be honest, I don’t think we really need to look too hard. Things stop being trending topics all the time. Things have to drop out of the list so that new things can come in. Otherwise the list would constantly be full of nonsense about Justin Bieber and Twilight. The Twitter trending topics algorithm can’t possibly just measure the popularity of topics. That would be incredibly dull. Instead, what it does is to look for changes in popularity. A steady buzz of the same few million people talking about a particular topic doesn’t get noticed, but a sudden increase in the number of people discussing the same topic does. The Buffer blog has a good explanation of this and the official Twitter blog says much the same thing.

I’m sure that this won’t convince the conspiracy theorists. “Ah,” they’ll say, “That’s all very convenient. But that just gives Twitter an easy way to cover up their censorship..” Which is true, I suppose, but hardly a basis for a rational discussion.

And that’s the most disappointing thing to come out of this affair. The people making this accusations are fans of Christopher Hitchens. You would hope they’d be from the more rational end of the spectrum. You’d hope that they would be above making accusations like this without evidence. I guess no-one is immune from irrationality.

But I’m going to go out on a limb here. And lay my cards on the table. And other clichés that Hitchens would despise.

Twitter (probably) didn’t censor the #GodIsNotGreat hashtag.

Update: The author of the tweet I quoted above seems to agree with me.

Richard WM Jones: rich

2011-12-16T23:29:28+00:00

Hardly need to say much more than what is said already in the news item.

davblog - Dave Cross: Hitchens’ Last Laugh

2011-12-16T14:34:55+00:00

This morning I woke up to the terrible (although not completely unexpected) news that Christopher Hitchens had died. The rational community has, of course, lost one of its most erudite and interesting members. But it seems that Christopher had one last trick up his sleeve.

As with most breaking news these days, I found out about his death from Twitter. I checked my Twitter feed as I got up at about 6am. A few people that I follow were already awake and discussing it. As a mark of respect, many of those tweets were tagged with the name of Hitchens’ best known book “God Is Not Great“. And then more and more people started to do that. And before too long, the hashtag #GodIsNotGreat was listed as one of Twitter’s worldwide trending topics. At which point it started to go a bit weird.

All around the world religious people who knew nothing at all about Christopher Hitchens, his books or his death were looking at Twitter and seeing the tag #GodIsNotGreat. And that annoyed many of them immensely. So they started tweeting on the subject. Their tweets seemed to largely fall into three categories.

1/ What is this? And why is it trending?

2/ Attempts to inject their own beliefs into the stream – “God isn’t just great – he’s the GREATEST!!” (from someone called foolishdenise – you couldn’t make this up)

3/ Threats to kill whoever had started the hashtag (all very Christian) [UPDATE: Replaced a tweet with a rather NSFW background with another expressing the same sentiment]

Of course, all of these new tweets all included the hashtag. So that just helped ensure that the hashtag became even more popular. Hitchens fans replied, pointing out why the hashtag was trending (and inviting them to read the book) and the hashtag was tweeted and retweeted and commented on and argued over more than pretty much any other hashtag I’ve followed all year. For most of the morning the Tweetdeck column I set up to follow the tag was moving too fast for me to follow it.

At some point in the morning, the hashtag disappeared from the list of trending topics. Some people claimed that Twitter had removed it deliberately in response to the Christian death threats. But it seems slightly ironic for Hitchens fans to claim something like that without any firm evidence. I suspect that it’s more likely that once a hashtag reaches a plateau of activity then Twitter’s algorithm ignores it – otherwise the top trend would always be Justin Bieber (as two people pointed out to me). Apparently it’s still trending in Canada. But I’m not sure what that proves about anything.

One tweet in particular from luketadams summed things up for me.

Hitchens dies. His book #GodisNotGreat trends. Religious people threaten violence. The point of his book is proven. Hitchens for the win.

It’s tempting to imagine Hitchens looking down on the storm that his death has caused and laughing. But that would go against everything that he believed in.

So don’t do that. Instead, reread his articles, buy his books, watch videos of him demolishing his opponents in debate. And remember the great mind that we have lost.

Planet GLLUG

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