Can’t update WordPress, need to reboot the VPS

PHP’s opcache module causes this kind of behaviour.

Disable this module by editing the file at /etc/php5/mods-available/opcache.ini and placing a semicolon like this.

;zend_extension=opcache.so

And restart PHP5-FPM/web server service.

If you are not comfortable editing these files add these lines to the top of your child theme’s functions.php file.

if ( is_admin() ):
    ini_set( "opcache.enable", "0" );
endif;