Hello,
I've had a similar problem -> On my installation, the server could not managed to access images from the libresource distributed filesystem. It seems that postgres tried to read and modify some files and of course, the postgres user did not have the same rights as the jonas user.
I also solved it by running Jonas with postgres user (Thanks to Rüdiger!). But that solution is pretty ugly, is there a better way to solve it. I'm also under Linux.
Thx.