PREUN

/bin/sh

if [ $1 -eq 0 ]; then

userdel -r xguest
groupdel xguest

# remove forbiden SSH:
if [ -e /etc/ssh/denyusers ]; then
	sed -i '/^xguest/d' /etc/ssh/denyusers
fi

fi

POSTIN

/bin/sh

if [ $1 -eq 1 ]; then
	xguest-add-helper
fi

Triggers

openssh-server

/bin/sh

if ! grep -q xguest /etc/ssh/denyusers; then
  echo xguest >> /etc/ssh/denyusers
fi