purge.sh

#!/bin/sh

# Credits to:
#  - http://vstone.eu/reducing-vagrant-box-size/
#  - https://github.com/mitchellh/vagrant/issues/343

aptitude -y purge ri
aptitude -y purge installation-report landscape-common wireless-tools wpasupplicant ubuntu-serverguide
aptitude -y purge python-dbus libnl1 python-smartpm python-twisted-core libiw30
aptitude -y purge python-twisted-bin libdbus-glib-1-2 python-pexpect python-pycurl python-serial python-gobject python-pam python-openssl libffi5
apt-get purge -y linux-image-3.0.0-12-generic-pae

# Remove APT cache
apt-get clean -y
apt-get autoclean -y

# Zero free space to aid VM compression
dd if=/dev/zero of=/EMPTY bs=1M
rm -f /EMPTY

# Remove bash history
unset HISTFILE
rm -f /root/.bash_history
rm -f /home/vagrant/.bash_history

# Cleanup log files
find /var/log -type f | while read f; do echo -ne '' > $f; done;

# Whiteout root
count=`df --sync -kP / | tail -n1  | awk -F ' ' '{print $4}'`; 
let count--
dd if=/dev/zero of=/tmp/whitespace bs=1024 count=$count;
rm /tmp/whitespace;
 
# Whiteout /boot
count=`df --sync -kP /boot | tail -n1 | awk -F ' ' '{print $4}'`;
let count--
dd if=/dev/zero of=/boot/whitespace bs=1024 count=$count;
rm /boot/whitespace;
 
swappart=`cat /proc/swaps | tail -n1 | awk -F ' ' '{print $1}'`
swapoff $swappart;
dd if=/dev/zero of=$swappart;
mkswap $swappart;
swapon $swappart;

On Ubuntu Server 12.04 (and possibly other distros) after executing lines 41-45 swap will be disabled upon reboot. The reason is that line 44 changes the uuid of the swap partition causing it to not match the uuid for the swap partition specified in /etc/fstab