[Nextcloud] Reset Preview Cache

To “reset” the preview cache 

1. Stop Webserver (apache / nginx)
   
2. Moved the appdata_instaceName/preview folder outside the appdata folder.
   You can just remove it if you are confident.
   
3. Run sudo -u www-data /usr/bin/php /var/www/nextcloud/occ files:scan-app-data
   to fix database
   
4. Start Webserver and Test everything works
   
5. Finish up (delete moved folder, etc).
   
   

Reference : Fairly new with nextcloud but preview folder has huge size – ℹ️ Support – Nextcloud community