TangledStrings 1.0 released!

I'm very pleased to announce the release of 1.0 of TangledStrings, a VIM plugin to help Puppet users avoid the confusion and frustration of editing a file that Puppet is managing and subsequently losing ones changes as it is replaced by Puppet's version.

Delightful Hybridisation

I've probably mentioned before that I really like the music of Hybrid, so I figured I'd pimp some stuff of theirs that's floated onto the web recently:

  • A couple of videos from their live set at Glastonbury this year (I'm very gutted that I didn't make it to see them)
  • Their latest Frisky Radio mixtape just hit Soundcloud, here.


Dream a little dream of me

Last night I had a lovely meal out and then saw Inception with Rike and some friends. I've really enjoyed all of Christopher Nolan's previous films and I think he does an excellent job of creating surprising and compelling stories. I'm not really going to say anything about the plot, other than to advise you avoid reading anything about it until you've seen it - not because there's anything particularly secret, but because it's nice to not have any preconceptions about what might happen. For me, the best films have me leaving the cinema totally caught up in their world, my mind reeling with the possibilities of what they have explored. Inception achieved this, and I want to see it again, although preferably at home on Bluray so I can hear every word of dialogue properly - a surprising shortcoming of one of London's flagship cinemas.

Random puppetry

I was talking to a colleague earlier about Puppet and its ability to install packages. I'd not really given it much thought beyond using it to install packages on classes of machines, but he mentioned one particular package which gets updated quite frequently, but is extremely low risk to update - tzdata. By setting this to "ensure => latest" rather than "ensure => present" I can forget about ever having to upgrade that package again \o/ Simple really, but it hadn't occurred to me.

Pick a letter, any letter

Earlier on my laptop suffered a slight mishap which resulted in a key popping off. I examined the mechanism and it didn't obviously go back on by itself, so I googled around a little and landed on the helpful chaps at I watched the video that pertains to my exact model, figured out which bits of metal had been slightly bent and a few minutes later I had everything back in working order. It's almost a shame I didn't need to buy anything from them in return for using their helpful video ;)

My python also spins webs

With Terminator 0.94 released I'm turning my little brain onto an idea I have for a web service and obviously I'm sticking with python. Clearly writing all the web gubbins by hand is mental, so I'm playing with Flask, a microframework for web apps. So far I'm really liking it, but it's taken a while to figure it and sqlalchemy out. I'm not at all convinced that this is going to be in any way scalable, but it's a nice way to test my idea :)

Who wants to see something really ugly?

I think it should be abundantly clear from my postings here that I'm not a very good programmer, and this means I give myself a lot of free rope to do some very stupid things. I'm in constant need of debugging information and in Terminator particularly where we have lots of objects all interacting and reparenting all the time. We've had a simple dbg() method for a long time, but I was getting very bored of typing out dbg('Class::method:: Some message about %d' % foo), so I decided to see what could be done about inferring the Class and method parts of the message. It turns out that python is very good at introspecting its own runtime, so back in January, armed with my own stupidity and some help from various folks on the Internet, I came up with the following:

# set this to true to enable debugging output
DEBUG = False
# set this to true to additionally list filenames in debugging
# list of classes to show debugging for. empty list means show all classes
# list of methods to show debugging for. empty list means show all methods

def dbg(log = ""):
    """Print a message if debugging is enabled"""
    if DEBUG:
        stackitem = inspect.stack()[1]
        parent_frame = stackitem[0]
        method = parent_frame.f_code.co_name
        names, varargs, keywords, local_vars = inspect.getargvalues(parent_frame)
            self_name = names[0]
            classname = local_vars[self_name].__class__.__name__
        except IndexError:
            classname = "noclass"
        if DEBUGFILES:
            line = stackitem[2]
            filename = parent_frame.f_code.co_filename
            extra = " (%s:%s)" % (filename, line)
            extra = ""
        if DEBUGCLASSES != [] and classname not in DEBUGCLASSES:
        if DEBUGMETHODS != [] and method not in DEBUGMETHODS:
            print >> sys.stderr, "%s::%s: %s%s" % (classname, method, log, extra)
        except IOError:

How's about that for shockingly bad? ;) It also adds a really impressive amount of overhead to the execution time. I added the DEBUGCLASSES and DEBUGMETHODS lists so I could cut down on the huge amount of output - these are hooked up to command line options, so you can do something like "terminator -d --debug-classes=Terminal" and only receive debugging messages from the Terminal module. I'm not exactly sure what I hope to gain from this post, other than ridicule on the Internet, but maybe, just maybe, someone will pop up and point out how stupid I am in a way that turns this into a 2 line, low-overhead function :D

A good day

Today has been about creating, not consuming. Apart from half-watching Primal Fear with Rike, I have spent the day fixing bugs in Terminator and playing with the Akai Synthstation app on my iPad. I suspect I'm not going to be ruling the clubs anytime soon, and the UI is pretty dreadful for composing music, but it has a good library of sounds and synth mangling knobs :) I even filmed myself playing some of the parts and edited them together into a little music video, but it's really very poor ;) Rike's going to be out for most of tomorrow, so I have to decide between doing more of what I've been doing today, playing PS3 games or going out myself. Tricky!

Terminator 0.94 released!

Lots of bug fixes and some improvements to the preferences are in this release, as well as a couple of new plugins for watching terminals for activity, or taking screenshots of individual terminals. See the changelog for full details.

The Lawnmower Man


This website shares a server with various other network services that form the foundation of my online life (i.e. IRC and Email) and I've been running into capacity issues in the last few months, so I'm running an experiment whereby I upgrade to brand new hardware (Quad Core i7, 8GB of RAM) and partition the available resources across virtual machines so the various network services are isolated into logical security zones.


I have plenty of experience using Xen for this sort of thing, but that's becoming more and more irrelevant in newer kernels/distributions. As much as I think that's a shame and a stupid upstream decision, I can't change it, so I need to move on to KVM and libvirt.


So, with the beefy new server booted up in a -server kernel and a big, empty LVM Volume Group I got to work creating some virtual machines. This post is mainly a reminder to myself of the things I need to do for each VM :)


These are the steps I used to make a VM with 1GB of RAM, 10GB / and 1GB of swap:

Create an LVM Logical Volume

lvcreate -L11G -n somehostname VolumeGroup

Create a VM image and libvirt XML definition

ubuntu-vm-builder kvm lucid --arch amd64 --mem=1024 --cpus=1 \
--raw=/dev/VolumeGroup/somehostname --rootsize=10240 --swapsize=1024 \
--kernel-flavour=server --hostname=somehostname \
--mirror= --components=main,universe \
--name 'Chris Jones' --user cmsj --pass 'ubuntu' --bridge virbr0 \
--libvirt qemu:///system --addpkg vim --addpkg ssh --addpkg ubuntu-minimal

Catchy command, huh? ;)


(building the VM will take a few minutes)

Modify the libvirt XML definition for performance

The best driver for disk/networking is the paravirtualised "virtio" driver. I found that ubuntu-vm-builder had already configured the networking to use this, but not the disk, so I modified the disk section to look like this:

<disk type='block' device='disk'>
  <source dev='/dev/VolumeGroup/somehostname'/>
  <target dev='vda' bus='virtio'/>

Modify the libvirt XML definition for emulated serial console

I don't really want to use VNC to talk to the console of my VMs, so I add the following to the <devices> section of the XML definition to make a virtualised serial port and consider it a console:

    <serial type='pty'>
      <target port='0'/>
    <console type='pty'>
      <target port='0'/>

Modify the libvirt XML definition for a better CPU

I'm running this on an Intel Core i7 (Nehalem), but libvirt's newest defined CPU type is a Core2Duo, so we'll go with that in the root of the <domain> section:

<cpu match='minimum'>

Import the XML definition into the running libvirt daemon

virsh define /etc/libvirt/qemu/somehostname.xml

Mount the VM's root filesystem

The Logical Volume we created should be considered as a whole disk, not a mountable partition, but dmsetup can present the partitions within it, and these should still be present after running ubuntu-vm-builder:

mkdir /mnt/tmpvmroot
mount /dev/mapper/VolumeGroup-somehostnamep1 /mnt/tmpvmroot

Fix fstab in the VM

Edit /mnt/tmpvmroot/etc/fstab and s/hda/vda/

Configure serial console in the VM

Edit /etc/init/ttyS0.conf and place the following in it:

    # ttyS0 - getty
    # This service maintains a getty on ttyS0 from the point the system is
    # started until it is shut down again.
    start on stopped rc RUNLEVEL=[2345]
    stop on runlevel [!2345]
    exec /sbin/getty -L 115200 ttyS0 xterm

Edit /boot/grub/menu.lst and look for the commented "defoptions" line. Change it to:

    # defoptions=console=ttyS0 console=tty0

(the default "quiet splash" is not useful for servers IMHO)

Unmount the VM's root filesystem

umount /mnt/tmpvmroot
rmdir /mnt/tmpvmroot

Start the VM

virsh start somehostname

SSH into the VM

I didn't specify any networking details to ubuntu-vm-builder, so the machine will boot and try to get an address from DHCP. By default you'll have a bridge device for libvirt called virbr0 and dnsmasq will be running, so watch syslog for the VM getting its address.


you should now be in your VM! Now all you need to do is configure it to do things and then fix its networking. My plan is to switch the VMs to static IPs and then use NAT to forward connections from public IPs to the VMs, but you could bridge them onto the host's main ethernet device and assign public IPs directly to the VMs.