Context : I was first using geoserver as a standalone (platform independent binary) version on Ubuntu. Almost everything is fine. But the jetty version it is built on is really old (6.8.1) and deprecated according to the eclipse website (we are now at ver. 9 : http://download.eclipse.org/jetty/)
So I decided to remove this installation of geoserver, upgrading my java installation (from opendjdk-7 to openjdk-8), and installing latest jetty version.
Under the webapps/ directory of jetty, I have now extracted the latest stable geoserver web archive (2.8.1) (http://geoserver.org/release/stable/).
And again, everything is almost fine, except that when I shutdown jetty server, and start it again after some time, geoserver is just like it was the first time accessing it : I have to reset all passwords, parameters, layers, and so on...
Question : How do I make every changes on geoserver permanent just like it was with the standalone version?