If you’re like me there is a box of hard drives sitting in a dusty corner somewhere. Some are mine, some are others’, but they are all in a failed or semi-failed state. So, why have I lugged them around? I’ve been a bit paranoid about throwing them away. Some of the hard drives are encrypted, others aren’t, and the drives from friends certainly aren’t. Although the chances of somebody getting the drive from a landfill and restoring it is minimal, I never wanted to take the chance.
So, I kept lugging a bag of drives through each move.
My friend Clinton has recently returned from Europe, and he brought me a gift: a Swiss-made Victorinox, the ‘CyberTool’. After playing with it for several minutes I noticed it came with a Torx 8, 10 and 15 bit. This was a reminder that one method of mostly disabling a hard drive is to destroy the platters.
Other methods I have heard are to use a hammer and nails - which I unfortunately don’t have in our tiny apartment. Whilst finishing Dexter I started pulling apart the box of hard drives, and it surprisingly didn’t take long to disable them.
Step 1: Remove Torx screws

Hint: Don’t forget the screw covered under the paper.
Step 2: Use a flathead and pop off the cover

Step 3: Stare at the shiny platters

Step 4: Scratch platters with flathead, and bend platters if possible

Step 5: Dispose of bits and pieces

Warning! The CyberTool didn’t have a Torx small enough to open the 2.5" hard drives, but I could just use a pair of pliers to lift up the cover and jam a flathead in there. However, and here’s the warning, 2.5" platters are sometimes not made of metal. I forgot about this on the third 2.5" hard drive and covered the desk I share with YS with shards of glass.

Recently I tried editing my Cisco’s ACL at home on the train. It went something like this:

• I logged in
• I started updating the ACL
• I hit a blackspot in my 3g coverage
• My command stops at “router(config)#access-”
• I get an alert saying my home internet was down

Although it is simple enough to just ask her to “flip the switch on the black box”, I still don’t like doing it. Plus, if she’s not home, I’m stuck. This accident immediately reminded me of one of a trait of the ‘reload’ command: it can be scheduled.

In the case of updating a device remotely, it is as easy as:

router# reload in 2
router# conf t
router(config)# [type in desired commands]
router(config)# exit
router# reload cancel

If the commands are entered in fine, then cancel the reload. If there is a problem, then the router will reboot and resort to the startup config.

If you want to use Graphserver to do some analysis with GTFS, you will need to convert GTFS into the database. This is how I did it.

Get an appropriate AMI from Amazon’s EC2

I used the following AMI. If you have enough memory, you don’t need to do this.

ami-7000f019

Lookup and read the GTFSDB INSTALL.txt document

Prepare system

sudo apt-get install mercurial
hg clone https://gtfsdb.googlecode.com/hg/ gtfsdb
sudo apt-get install python-setuptools
sudo easy_install psycopg2
sudo apt-get install build-essential

Download GTFS database

ubuntu@domU-12-31-39-00-5D-B8:/mnt/gtfsdb$ pwd
/mnt/gtfsdb
sudo python setup.py install
sudo wget http://cdn.kelvinism.com/google_transit.zip
sudo apt-get install python-psycopg2

EDIT 16-03-2025: I’ve since removed these files.

Prepare configuration file

#default.cfg
[options]
create = True
database = postgresql://nsw:[email protected]:5432/nsw
filename = /mnt/google_transit.zip
geospatial = True
#schema = None

Perform import

screen
python gtfsdb/scripts/load.py

I’ve been cleaning up my personal blog a bit, and I noticed that my tagging system recently broke. I’ve investigated the cause, and it appears to be because I removed some apps but the contenttypes remained. This meant that whenever I tried calling a tag with a TaggedItem that had been deleted, I was getting this error:

'NoneType' object has no attribute '_meta'

The solution is to first list all app_labels for contenttypes, and then delete any not in use.

In [61]: from django.contrib.contenttypes.models import ContentType
 
In [62]: for ct in ContentType.objects.all(): print ct.app_label
   ....:
picasaweb
lifestream
readernaut
delicious
mapfeed
comments
...

I could then delete the unused contenttypes.

ct_list = ["delicious", "flickr", "photologue", "twitter"]
 
for ct_label in ct_list:
    for ct in ContentType.objects.filter(app_label=ct_label):
        ct.delete()
    

And no more errors! For more details take a look at David’s article.

I recently had the desire to send small updates to my so called lifestream page via XMPP/GTalk. I played around with Twisted Words and several other Python XMPP clients, but I didn’t really want to keep a daemon running if unnecessary. It turns out imified took a lot of the pain out of it. The steps for me were as follows:
Create an account with imified, and create a URL, e.g. /app/api/
We then configure the urls.conf

urlpatterns = patterns('',  
    (r'^app/api/$', bot_stream),
)

We then create the necessary views. So, in views.py:

from django.shortcuts import render_to_response
from django.http import HttpResponse
from lifestream.forms import *
from datetime import datetime
from time import time
 
def bot_stream(request):
    if request.method == 'POST':
        botkey = request.POST.get('botkey')
        username = request.POST.get('user')
        msg = request.POST.get('msg')
        network = request.POST.get('network')
    
    if username == "[email protected]" or network == "debugger":
        blob_obj = Blob(id=time(), body=msg, service_name="Mobile",
        link="http://www.kelvinism.com/about-me/", published=datetime.now())
        blob_obj.save()
        resp = "OK"
    else:
        resp = "Wrong username %s" % username
    else:
        resp = "No POST data"
    return HttpResponse(resp)

To complete this little example, you can see what I used for my models.py

class Blob(models.Model):
    id = models.CharField(max_length=255, primary_key=True)
    body = models.TextField(max_length = 1024, null = True, blank = True)
    service_name = models.CharField(max_length=50, null=True, blank=True)
    link = models.URLField(max_length=255, verify_exists=False, null=True, blank=True)
    published = models.DateTimeField(null=True, blank=True)
 
def __unicode__(self):
    return self.id
 
class Meta:
    ordering = ['-published']
    verbose_name = 'Blob'
    verbose_name_plural = 'Blobs'
 
def get_absolute_url(self):
    return "/about-me/"

It maybe isn’t super elegant, but it works just fine, and maybe can provide a hint if somebody else is contemplating using a homebuilt xmpp solution, or just pawning it off on IMified.

I like using Ubuntu’s UFW command, but today I needed to allow outgoing ICMP. I received results as so:

$ ping 4.2.2.2  
PING 4.2.2.2 (4.2.2.2) 56(84) bytes of data.  
ping: sendmsg: Operation not permitted  
ping: sendmsg: Operation not permitted  
ping: sendmsg: Operation not permitted  

To allow outbound icmp I edited ‘before.rules’ and added the following lines.

$ sudo vi /etc/ufw/before.rules

# allow outbound icmp
-A ufw-before-output -p icmp -m state --state NEW,ESTABLISHED,RELATED -j ACCEPT
-A ufw-before-output -p icmp -m state --state ESTABLISHED,RELATED -j ACCEPT

I recently had the need to add some HTML to the label for a form field using Django. The solution is pretty easy, except I didn’t see it written explicitly anywhere, and I missed the memo of the function I should be using.
My form first just had the HTML in the form label as so:

from django import forms
 
class AccountForm(forms.Form):
    name = forms.CharField(widget=forms.TextInput(), max_length=15, label='Your Name (<a href="//www.blogger.com/questions/whyname/" target="_blank">why</a>?')

However, when I displayed it, the form was autoescaped.

This is generally a good thing, except my form obviously didn’t display correctly. I tried autoescaping it in the template, but that didn’t work. To resolve this you’ll need to mark that individual label as safe. Thus:

from django.utils.safestring import mark_safe
from django import forms
 
class AccountForm(forms.Form):
    name = forms.CharField(widget=forms.TextInput(), max_length=15, label=mark_safe('Your Name (<a href="//www.blogger.com/questions/whyname/" target="_blank">why</a>?)'))
    

It will now display correctly:

In [1]: from myproject.forms import *
 
In [2]: form = AccountForm()
 
In [3]: form.as_ul()
Out[3]: u'
<li><label for="id_name">Your Name (<a href="//www.blogger.com/questions/whyname/" target="_blank">why</a>?):</label> <input id="id_name" maxlength="15" name="name" type="text"></li>
'

There’s maybe another easier way to do this, but this worked for me.

I’ve started to get into Google’s App Engine again, and have started developing a simple product that I had a use for. The initial first draft was a quick 200 lines in webapp, and it worked great. However, I’m starting to find certain things quite cumbersome. I’m a huge fan of Django, and but also about keeping things as simple as possible, which is why I picked webapp to begin with.
I’m now considering making a swap to Django, but there are some development issues; namely, I’m using Ubuntu 10.04, Python 2.6, and Django 1.2. This setup presents several setbacks, as GAE has the requirement of Django 1.1 and Python 2.5. There are two solutions that I found: a) use virtualenv, which I’ve detailed, or b) chroot. This document will hopefully show how to configure a chroot environment of Ubuntu 9.10 and prepare it for Django on GAE. Using a jailed environment should allow you to edit your code with your normal IDE and VCS, but use Django 1.1 and Python 2.5.
First, I installed schroot and debootstrap.

$ sudo apt-get install schroot debootstrap

Second, I edited /etc/schroot/schroot.conf and added the following section to the end.

[karmic]
description=karmic
type=directory
location=/var/chroot/karmic
priority=3
users=kelvinn #your username goes here
groups=admin
root-groups=root
run-setup-scripts=true
run-exec-scripts=true

Third, I created the directories needed for the jailed environment and installed karmic.

$ sudo mkdir -p /var/chroot/karmic
$ sudo debootstrap --arch i386 karmic /var/chroot/karmic

Forth, I logged into the jailed environment and updated packages, installed Python 2.5 / Django 1.1. Make sure to note that I don’t call ‘python’, I call ‘python2.5’.

$ sudo schroot -c karmic
(karmic)root@kelvinn-laptop:~# apt-get update
(karmic)root@kelvinn-laptop:~# apt-get install python2.5
(karmic)root@kelvinn-laptop:~# cd /usr/src
(karmic)root@kelvinn-laptop:~# apt-get install wget
(karmic)root@kelvinn-laptop:/usr/src# wget http://www.djangoproject.com/download/1.1.2/tarball/
(karmic)root@kelvinn-laptop:/usr/src# tar -xpzf Django-1.1.2.tar.gz
(karmic)root@kelvinn-laptop:/usr/src/Django-1.1.2# python2.5 setup install
(karmic)root@kelvinn-laptop:/usr/src/Django-1.1.2# exit

Lastly, I log in as my normal user, and start the app. Let’s say I have a folder called ‘~/gaeapps’ for my GAE stuff, and that’s where I put the SDK.

$ scroot -c karmic
(karmic)kelvinn@kelvinn-laptop:~/gaeapps$ ls
google_appengine  myproject
(karmic)kelvinn@kelvinn-laptop:~/gaeapps$ google_appengine/dev_appserver.py myproject

All my Django sites are running 1.2, which poses a conflict with writing apps for Google’s App Engine, as use_library currently only supports < Django 1.1. There are two solutions that I found: a) use virtualenv, or b) chroot, which I’ve already detailed. This document will hopefully show you how to create a virtual environment to use a secondary django version, especially for GAE. Of the two options, I think this one is a bit quicker, but there will likely be tradeoffs that a chroot environment can deal with better, e.g. python imaging (I don’t use it for GAE).
First, install PIP and virtualenv:

kelvinn@kelvinn-laptop:~/workspace$ sudo easy_install -U pip
kelvinn@kelvinn-laptop:~/workspace$ sudo pip install -U virtualenv

Second, configure an environment for any app that will use Django 1.1:

kelvinn@kelvinn-laptop:~/workspace$ virtualenv --python=python2.5 --no-site-packages django-1.1
New python executable in django-1.1/bin/python
Installing setuptools............done.
kelvinn@kelvinn-laptop:~/workspace$ pip install -E django-1.1 yolk
kelvinn@kelvinn-laptop:~/workspace$ pip install -E django-1.1 Django==1.1

Now, download the python GAE sdk and put it in the django-1.1 folder. I also just dump any project directory requiring Django 1.1 into this django-1.1 folder, although I guess you could create a virtualenv for each project. The last thing to do is start the virtual environment, and run the GAE app.

kelvinn@kelvinn-laptop:~/workspace$ source django-1.1/bin/activate
(django-1.1)kelvinn@kelvinn-laptop:~/workspace$ yolk -l
(django-1.1)kelvinn@kelvinn-laptop:~/workspace$ cd django-1.1
(django-1.1)kelvinn@kelvinn-laptop:~/workspace/django-1.1$ ls
bin  google_appengine  include  lib  myproject1 myproject2
(django-1.1)kelvinn@kelvinn-laptop:~/workspace/django-1.1$ google_appengine/dev_appserver.py myproject1

When you’re all finished, you can jump out of virtualenv:

(django-1.1)kelvinn@kelvinn-laptop:~/workspace/django-1.1$ deactivate

Update: You’ll find this article especially interesting if you get an error such as the following:

UnacceptableVersionError: django 1.1 was requested, but 1.2.0.beta.1 is already in use

One thing I love about open source stuff is that the developers usually take great care to allow awesome debug messages. There’s a catch-22, however: how much logging to enable? Today I was creating a Postfix/Dovecot/Postgresql install and I kept getting an error message in mail.log, but it wasn’t very helpful.

Luckily you can turn up the verbosity in Postfix for error messages. You’ll need to find out what component is in error, e.g. “postfix/virtual[4467]: warning:”, and then open master.cf. Add a -v to the end of the daemon that’s faulting, and you’ll get more logging than you know what to do with.

virtual   unix  -       n       n       -       -       virtual -v

I hope this helps somebody. You can read more debugging tips on the Postfix DEBUG readme.