Check whether your wordpress installation have correct file and folder permission for proper functioning. Improper file permission may lead to file upload error, site update error etc. and it may also lead to security threats also. Let’s assume you have installed WordPress in /var/www/wbxpress, then you need to execute the following commands. Don’t worry these commands are applicable for both the web servers apache or nginx.

Set Proper Ownership of the WordPress directory

sudo chown -R www-data:www-data /var/www/wbxpress

Set Proper File Permission

sudo find /var/www/wbxpress -type d -exec chmod 755 {} \;

Set Proper Folder Permission

sudo find /var/www/wbxpress -type f -exec chmod 644 {} \;

You can set file and folder permission from FTP also.