PREIN

/bin/sh

getent group docker > /dev/null || /usr/sbin/groupadd -r docker
exit 0

PREUN

/bin/sh

if [ $1 -eq 0 ] ; then 
        # Package removal, not upgrade 
        systemctl --no-reload disable --now docker >/dev/null 2>&1 || : 
fi

POSTIN

/bin/sh

if [ $1 -eq 1 ] ; then 
        # Initial installation 
        systemctl --no-reload preset docker >/dev/null 2>&1 || : 
fi

POSTUN

/bin/sh

if [ $1 -ge 1 ] ; then 
        # Package upgrade, not uninstall 
        systemctl try-restart docker >/dev/null 2>&1 || : 
fi