install xscreensaver in the usual way using the Synaptic Package Manager.
configure xscreensaver from the terminal using xscreensaver-demo (without privileges – no sudo su).
then how to autostart xscreensaver in debian jessie.
create a file in /home/yourname/.config/autostart called Xscreensaver.desktop thus:-
for yourname read your account name. apart from the line Exec=xscreensaver this probably doesn’t do much.
and that’s it. i share this after months of trawling the internet and not finding out how to do it.
xscreensaver will create a file called .xscreensaver in /home/yourname/.
this worked for me.