How to override default Jahia login page
There are a couple of ways in which this can be achieved:
1. You can override the error_401.jsp, which is the JSP being served by Jahia when a 401 error is raised in live
You have 2 possibilities for overriding this JSP, you can create your own error_401.jsp (you have to use this exact name) and :
2. You can define a Java class implementing LoginUrlProvider
and defining the URL you want to redirect to for login page.
We have an example module showing how to do this on Github : https://github.com/Jahia/loginlogout-url-provider