Unless there is a bug I don"t know about, the cache folders (books and comics) are cleared when you click the "clear database" button. There is no need to clear them manually.
And this will indeed rebuild your whole database, rescaning all files and regenerating all covers.

It has to be in the command line you use to launch Ubooquity.

So if you followed Matthew's tutorial, you have to modify the /etc/init/ubooquity.conf file.
If you want, just post here the script you use to start Ubooquity and I'll indicate what changes to make.

Solution found: see this thread.

Solution found: see this thread.

Thanks for your feedback. It will allow me to update the FAQ and the installation instructions for Synology devices so that other users don"t have the same problem.

Ok, installation done. I have been able to reproduce the problem.
And then fix it by adding the following Java parameter:

-Dfile.encoding=UTF-8

Could you try launching Ubooquity with it and let me know if it solves the problem for you ?
Your command line would be something like that:

java -Dfile.encoding=UTF-8 -jar Ubooquity.jar -webadmin

(you have to be in the same directory as the "Ubooquity.jar" file)

The connection probably fails because Ubooquity is not running anymore (that's what your log says).
As to why it stops, I'll let Synology experts answer as I don't own one myself.

Thanks. :)

For now I'm trying to install DSM on a virtual machine. I'll see how it goes.