PREIN

/bin/sh

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

PREUN

/bin/sh

 
if [ $1 -eq 0 ] && [ -x /usr/bin/systemctl ]; then 
        # Package removal, not upgrade 
        /usr/bin/systemctl --no-reload disable --now docker || : 
fi

POSTIN

/bin/sh

 
if [ $1 -eq 1 ] && [ -x /usr/bin/systemctl ]; then 
        # Initial installation 
        /usr/bin/systemctl --no-reload preset docker || : 
fi

POSTUN

/bin/sh

 
if [ $1 -ge 1 ] && [ -x /usr/bin/systemctl ]; then 
        # Package upgrade, not uninstall 
        /usr/bin/systemctl try-restart docker || : 
fi