De acordo com Dill no Ubuntuforums você pode implementar um script de logout assim:
If you don't already have one, create a .bash_logout file:
http://rcsg-gsir.imsb-dsgi.nrc-cnrc.gc.ca/documents/advanced/node125.html
Here are the contents of my default .bash_logout on an Ubuntu machine and Debian server:
# ~/.bash_logout: executed by bash(1) when login shell exits.
# when leaving the console clear the screen to increase privacy
if [ "$SHLVL" = 1 ]; then
[ -x /usr/bin/clear_console ] && /usr/bin/clear_console -q
fi
O feedback parece bom para a sua resposta. Link para referência