I have a question.
My vanilla version is 2.1.1, is that possible to upgrade directly to 3.2.
Or we must update to each version like 2.2 , 2.3, 2.4 ...
So is that possible to install the newest version, and restore database later to avoid All users need to reset their password?
Your can start with a fresh and connect old database later - yes.
But to my understanding it will not change anything.
Structure update of database is still needed.
I do not know under which circumstances password resets would be required.
Password are saved as hashes so that you cannot recover the password from what is saved in the database. Therefore there is no way to transform the old password into the new one. I hope I can explain it: there has been a Vanilla version where passwords where matched with the old method and afterwards saved with the new "format". Therefore all users who logged in the forum while that version has been used, where ported to that new format without even noticing it. That transformation step isn't there in Vanilla any more. So forum members have to reset their password. There is no way to avoid that.
But who cares? Write a message: "Heads up! There's a major forum update coming. You will have to reset your password when the update is done". Then your users are prepared.
After the update show another message "Forum has been updated. Your password has become invalid. Please reset it". The current Vanilla version uses a more secure algorithm. So your users have nothing to complain about.
So, I will update 2.1.1 to 2.8 first then 2.8 to 3.2 or 2.1.1 direct to 3.2 ?
Cause what I saw when download 3.2 version is "Version 2.8 required plus php 7.2"
Just do it 😉
Start with a backup: zip your complete Vanilla folder and make a backup of your database. Nothing can really go wrong after that!
Read the documentation page:
Normally an upgrade can be done by just copying over the new files. In this case, you additionally need to delete files and folders. Which files and folders to delete can be found in the link above.
Some old plugins do not work with the current version. Therefore the first step (after the backup) I would make would be to disable all plugins and applications (with exception for the vanilla and the conversations application and the HTMLawed plugin). After your update you should re-enable all those plugins one by one and test if they still work before you enable the next plugin.
But again: simply do it. Inform your users about 2 hours of downtime and your safe. In that time you either have finished upgrade (although it should be possible to upgrade in minutes) or you have found there are problems that would require further investigation and you need to restore the forum from the backup.
If you face the "Something has gone wrong" error message, please take a look at the docs on how to get more information, so when you really have to ask for help, you could tell us what the problem has been.