Yeah that's right. It's a script in ./debian called postinst or <packagename>.postinst that runs after the installation. .......
#!/bin/sh gtk-update-icon-cache -f /usr/share/icons/hicolor chown -R user /opt/myapp/ set -e case "$1" in configure) ;; abort-upgrade|abort-remove|abort-deconfigure) ;; *) echo "postinst called with unknown argument \`$1'" >&2 exit 1 ;; esac exit 0