As what as you like

Jul 6, 2010
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
DEBUGFILES = False
# list of classes to show debugging for. empty list means show all classes
DEBUGCLASSES = []
# list of methods to show debugging for. empty list means show all methods
DEBUGMETHODS = []

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)
        try:
            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)
        else:
            extra = ""
        if DEBUGCLASSES != [] and classname not in DEBUGCLASSES:
            return
        if DEBUGMETHODS != [] and method not in DEBUGMETHODS:
            return
        try:
            print >> sys.stderr, "%s::%s: %s%s" % (classname, method, log, extra)
        except IOError:
            pass
```
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
Jul 6, 2010
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 :)
Jul 4, 2010
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.
Jul 4, 2010
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!
Jun 8, 2010
The Lawnmower Man
Introduction

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.

Whining

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.

Resolution

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 :)

Action

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=http://archive.ubuntu.com/ubuntu/ --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? ;)

Wait

(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'/>
</disk>
```
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'/>
    </serial>
    <console type='pty'>
      <target port='0'/>
    </console>
```
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'>
  <model>core2duo</model>
</cpu>
```
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]
    respawn
    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.
```
ssh cmsj@192.168.122.xyz
```
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.

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Complete post archive

As what as you like

Who wants to see something really ugly?

My python also spins webs

Terminator 0.94 released!

A good day

The Lawnmower Man

Introduction

Whining

Resolution

Action

Create an LVM Logical Volume

Create a VM image and libvirt XML definition

Wait

Modify the libvirt XML definition for performance

Modify the libvirt XML definition for emulated serial console

Modify the libvirt XML definition for a better CPU

Import the XML definition into the running libvirt daemon

Mount the VM’s root filesystem

Fix fstab in the VM

Configure serial console in the VM

Unmount the VM’s root filesystem

Start the VM

SSH into the VM