NexoPOS is always up to add awesome features. Updates are splited in 3 parts.
We have minor update what fix minor issue and whose version looks like this 2.x.x
Then we have a medium update which bring new features but doesn't require huge migration process and whose version looks like this 2.x
And finally, we have the major update which bring huge modification on source code and require strict migration process. The version of major update distinguish himself by the first number which regulary changes, and looks like this x.0 or x.1.
If you can't read more informations about that on the readme file related to the current version you have, you can check the blog where you can see more instructions on how to install your current version.
Backup Everything First :
In that situation, you'll only need to make a backup of your database file located on application/config/ and backup all your images located on public/upload.
Delete current installation :
Now you can delete current installation and install the update. Then restore your database.php file and your images.
The same rules for minor version is applyied here.
For this update, you'll have to make a database migration. Each NexoPOS installation will have a migration.txt file located at the root of the projet.
You'll have to follow previous rules for minor and medium version and also make a database migration.
Database migration won't be always required. A major update can comes without any database migration.