Files related to upgrade
In the /conf folder there is a file called _maintenance.html. If you rename this file to maintenance.html (no _ at the beginning), it will put your b2evolution website into maintenance mode, serving a 503 "Not Available" response to any user…
This will allow b2evolution to perform an auto-upgrade without leaving unwanted files on your server and without overwriting file you don't want to overwrite (e-g: favicon.ico). In this file you can give all kinds of instructions to b2evolution as to how to handle files during upgrade. Look at the comments in the file for more information.
A list of files and directories to be ignored from backup on automatic upgrade. List on file or directory per line. Here is an example of file contents you could use: