Super awesome, simple, fast and robust deploy system. It has only 2 drawbacks: flexible by changing code and user must know what he does. Part 1 - prepare access to target machine.

stork-deploy-init.bash

#!/bin/bash
# Stop on errors
set -e

# Config
: ${user=stork-deploy}
: ${ssh_public_key="ssh-dss AAAAB3NzaC1kc3MAAACBAIbzNCxj+N8ZGcEeel1jMfy9MpBOoLUQXR+fxgqsXYiFkAB6e2deqKHXh+TuntWQwsoPcXi2/0UaWZkgR3JmJxrqFM3/aAeUUupDFLnUFSuz+L2y4hke8GAeLHuzaZ30HfvDU+AO4uQF6obLl5xs88H5BYPvmzhxQcPdOiwkK1XDAAAAFQCwh2kXaGbJGWE+Jaw78cxKNq+JHQAAAIA4X3JfuQ6eYm0N1EWPcWf46rTT0O0TNnBXlhNRhSQNnxbcLjF8ZYG/tYLRJA/J8dMgi/4ZojW4Hq7CluYq68ycf2FOS3S60vdoEv++q7oq8jKHyfQtzo+Jq8q0yMXd+PBnHp7s4v8AHK7ifz/LotCfg7d9+XAbCt//qjwZgPTulQAAAIBzptzN3d+yLu63MraeVdvz5nYDCwiy94FKaSSfPbHWH9iKb8jyJ1smrsM4SV9/ongsMAnDIA340HYFZqBY/iZEak84BTnjA89sZmUP/8E1Ou7WL/Lsx/kMfLuh4zANoqzMbwir7zm69x5ZqRhSqBs2J8iLx2hCX5zwWhoDnpVIUg== stork deploy"}
: ${sudoers_conf="/etc/sudoers.d/$user"}
version=1

install() {
	# Check requirements
	test "`whoami`" = "root"
	which chmod >/dev/null
	which sudo >/dev/null
	which useradd >/dev/null
	which whoami >/dev/null

	echo "- create user"
	useradd --create-home --system --user-group "$user"
	sudo -inu "$user" bash -ec "mkdir ~/.ssh; echo '$ssh_public_key' >~/.ssh/authorized_keys; chmod go-w ~; chmod -R go-rwx ~/.ssh"

	echo "- grant sudo"
	test ! -f "$sudoers_conf"
	echo "$user ALL=(ALL) NOPASSWD: ALL" >"$sudoers_conf"
	chmod 0440 "$sudoers_conf"
	sudo -inu "$user" bash -ec 'echo -n "testing sudo... "; s=`sudo -n whoami`; test "$s" = "root" && echo ok'
}

revoke() {
	echo "- revoke sudo"
	rm -f "$sudoers_conf"
}

remove() {
	opt=""
	if [ -z "$1" ]; then
		: # nothing
	elif [ "$1" = "purge" ]; then
		opt="--remove"
	else
		echo "remove: invalid option: $1" >&2
		exit 1
	fi

	# Check requirements
	test "`whoami`" = "root"
	which userdel >/dev/null

	echo "- userdel $opt $user"
	userdel $opt "$user"
}

case "$1" in
--version)
	echo "Version: $version"
	exit 0
	;;
"")
	echo "Usage: curl https://gist.github.com/temoto/5036687/raw/stork-deploy-init.bash |sudo bash /dev/stdin {install | purge | revoke | uninstall}"
	echo "Do not forget to open a safety root shell in case of problems with sudoers.d."
	echo "Read the code."
	exit 1
	;;
install)
	install
	;;
purge)
	revoke
	remove purge
	;;
revoke)
	revoke
	;;
uninstall)
	revoke
	remove
	;;
esac