Post-install script to disable SSH password authentication, install latest Docker with AUFS on Ubuntu 14.04 VMs

postinstall.sh

#!/bin/bash
# Disable password authentication
sudo grep -q "ChallengeResponseAuthentication" /etc/ssh/sshd_config && sed -i "/^[^#]*ChallengeResponseAuthentication[[:space:]]yes.*/c\ChallengeResponseAuthentication no" /etc/ssh/sshd_config || echo "ChallengeResponseAuthentication no" >> /etc/ssh/sshd_config
sudo grep -q "^[^#]*PasswordAuthentication" /etc/ssh/sshd_config && sed -i "/^[^#]*PasswordAuthentication[[:space:]]yes/c\PasswordAuthentication no" /etc/ssh/sshd_config || echo "PasswordAuthentication no" >> /etc/ssh/sshd_config
sudo service ssh restart

# Install latest Docker
sudo apt-get update
sudo apt-get -y install linux-image-extra-$(uname -r)
sudo sh -c "wget -qO- https://get.docker.io/gpg | apt-key add -"
sudo sh -c "echo deb http://get.docker.io/ubuntu docker main\ > /etc/apt/sources.list.d/docker.list"
sudo apt-get update
sudo apt-get -y install lxc-docker

sed -i 's/#PasswordAuthentication.*/PasswordAuthentication no/' /etc/ssh/sshd_config

I just came across this gist, and I think you can shorten that sed and echo into sed in place editing like above. And you probably don't need sudo sh -c. sudo wget should do.