Hi,
Joomla! 2.5.1
Joomla Multi Sites version: 1.2.76
Version de la liste des patches: 1.2.77

I don't succeed in creating a slave site : I have the "classic" can't connect database from back-end.
I have create the future databse manually
I have granted the actual Joomla SQL user on the future database and still don't working after hours of testing...

Thanks for your help

If you have a message where you can not connect the DB, this mean that you have an error in your DB parameters.

Perhaps you could start to create a websites in your current DB and later try changing the parameters to the DB. I hope this will help you to setup all the parameters correctly and finally to setup the DB connection correctly.

If you create a fresh slave site, verify the parameter that you enter in the Joomla Installer.