How do I prevent Diodon to not save history in disk?

This is a good question. Unfortunately for Diodon it is really difficult to determine whether a clip is a password or not.

There are some ideas on the way though which might help you. E.g. a plugin to remove clips see https://blueprints.launchpad.net/diodon/+spec/ideas-for-plugins or a possible zeitgeist integration which would make it possible if it works to black list application to be adding clips to the history (e.g. black list your password manager application if you have such).

Currently though the only thing what you can do is to Clear the history completely. What I did is to encrypt my home directory with eCryptfs which makes storing of the password less critical as well.

Of course, if there are any other ideas how to overcome this issue let me know and we can see what we can do.

Thanks Oliver Sauder, that solved my question.

I think it will be a good function to add. It is not too safe to store history on disk. I don't know is it possible to add such check box - Delete history on close or system shut down, but this is I really lack of.

For now the workaround will be as explained in comment 2.

We are currently working on replacing the xml history with a zeitgeist backend. We will need to reassess how such can be done with Zeitgeist as there are already Privacy options available.