post_install() {
	grep -qe '^/bin/nullshell$' etc/shells || echo '/bin/nullshell' >> etc/shells
	grep -qe '^/usr/bin/nullshell$' etc/shells || echo '/usr/bin/nullshell' >> etc/shells
}

post_upgrade() {
	post_install
}

pre_remove() {
	sed -i -r '/^(\/usr)?\/bin\/nullshell$/d' etc/shells
}