php7.4 opcache.preload - Errors on fpm start

Question

I'm upgrading to php7.4 and want to take advantage of the new opcache preloading.

When I service php7.4-fpm start I get the following errors:

NOTICE: PHP message: PHP Warning:  PHP Startup: failed to open stream: Permission denied in Unknown on line 0
NOTICE: PHP message: PHP Fatal error:  PHP Startup: Failed opening required '/mnt/a/b/c/opcachePreload.php' (include_path='.:/usr/share/php:/mnt/a/b/c:/mnt/a/b/d') in Unknown on line 0
php7.4-fpm.service: Main process exited, code=exited, status=70/n/a
Failed to start The PHP 7.4 FastCGI Process Manager.

My fpm/php.ini includes the following opcache settings:

include_path              = ".:/usr/share/php:/mnt/a/b/c"

opcache.save_comments           = 1
opcache.max_accelerated_files   = 7963
opcache.interned_strings_buffer = 16
opcache.fast_shutdown           = 1
opcache.revalidate_freq         = 0

opcache.validate_timestamps     = 0
opcache.memory_consumption      = 128
opcache.preload                 = /mnt/a/b/c/opcachePreload.php
opcache.preload_user            = www-data

I've tried having the opcachePreload.php contain only <?php and the error still happened, normally it contains something like this, with a couple of absolute paths in the array:

<?php
declare(strict_types=1);

$scriptsArr = [
    'path',
    'path',
];
foreach ($scriptsArr as $fileStr) {
    opcache_compile_file($fileStr);
}

I've tried a range of different levels of file-permissions on it (0600, 0700, 0770, 0777, owned by root), currently ls -l /mnt/a/b/c/opcachePreload.php shows:

-rwxrwxrwx 1 www-data www-data 336 Dec 26 15:11 /mnt/a/b/c/opcachePreload.php

Is it a file-permission problem, or a conflict in the configurations, or a php7.4 bug, or something else?

Is the opcache.preload interpreted as some sort of relative path instead of absolute? (I've tried opcache.preload = ./opcachePreload.php )

What else can I try?

Answer 1

Try to put your opcachePreload.php inside for example /var/www/html and change opcache.preload to

opcache.preload = /var/www/html/opcachePreload.php

If that works then www-data doesn't have permission to access files in /mnt/a/b/c/