Disable third-party modules before core update I have a D8 (8.5.6) installation which I have been trying to upgrade to 8.6 since it came out. It is on a shared hosting account which does not allow drush, so FTP it is. During the database update, it fails and I end up with the proverbial white screen of death. Before delving into detail troubleshooting, I want to disable all the third-party modules, and see if this works. If successful, I want to enable the third-party modules, one by one.

Is that a "good practice" type of approach?

The point is to quickly identify whether it is a contrib module which causes problems are the core install. Normal troubleshooting procedures would follow in any case.
The one and only way to solve your problem responsibly is the following.


Download all files to your local machine.
Where you have a web development setup. And Drush.
Download the database.
Setup the page on your local machine, import the database and re-do locally what you were currently trying to do on the live server.
Use your local Drush and whatever other tools you can get to check error messages, server logs, debug output etc.
Drop and re-import the local database and repeat every step until you have reproduced the problem often enough to know what went wrong in the first place.
Fix your live page.


And finally:

Never ever again update stuff untested on the live server. And have the database backed up let's say at least once a week. Good luck!