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Sorry to hear you’re facing problems 
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In order to help you as quickly as possible, before clicking Create Topic please provide as much of the below as you can. Feel free to use a pastebin service for logs, otherwise either indent short log examples with four spaces:
example
Or for longer, use three backticks above and below the code snippet:
longer
example
here
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 20.0.5): 25.0.0
Operating system and version (eg, Ubuntu 20.04): Arch Linux
Apache or nginx version (eg, Apache 2.4.25): 1.23.1
PHP version (eg, 7.4): 8.1.11
The issue you are facing:
Upgrade to version 25.0.0 had issues, first time I’ve ever had issues with a Nextcloud upgrade.
When running the web updater I encountered the message “Possible CSRF attack. Connection will be closed.” There was no way for me to update via the web updater. So I upgraded via occ which had no problems initially.
I was initially able to log into the web interface. After closing that particular session I can’t log in anywhere. I can access the login screen and input credentials, but the page just reloads with no error.
I’ve seen this behavior occasionally, but I’ve always been able to log in on a subsequent attempt. Now I can’t access the web interface at all. Server operations like file sync and webDAV calendar sync are still functioning without incident – I just can’t access the web interface.
This installation’s configuration hasn’t been touched for six months. It has been completely functional up until I upgraded to NC 25.
Only thing I did in the web interface before closing that last successful session was change the background from the default.
Web root is /srv/http. NGINX user is “http.” “http” user and group own everything in the web root. Other applications on the same server still run perfectly fine.
Is this the first time you’ve seen this error? (Y)
Steps to replicate it:
-
Go to Nextcloud login page
-
Input any username/password combo – even one intentionally wrong
-
Login screen reloads, no error output, I get HTTP 500 Internal Server Error in the browser on the request for /core/img/app-background.jpg
The output of your Nextcloud log in Admin > Logging:
{"reqId":"jqaNVAvBHJRq3XeNtujT","level":0,"time":"2022-10-21T02:34:36+00:00","remoteAddr":"redacted","user":"--","app":"no app in context","method":"GET","url":"/nextcloud/apps/dashboard/","message":"Current user is not logged in","userAgent":"Mozilla/5.0 (Windows NT 10.0; rv:106.0) Gecko/20100101 Firefox/106.0","version":"25.0.0.18"
"reqId":"0lxTYaJUZgBUXGLi0ghK","level":3,"time":"2022-10-21T02:34:37+00:00","remoteAddr":"172.71.150.21","user":"--","app":"index","method":"GET","url":"/core/img/app-background.jpg","message":"The requested uri(/core/img/app-background.jpg) cannot be processed by the script '/nextcloud/index.php')","userAgent":"Mozilla/5.0 (Windows NT 10.0; rv:106.0) Gecko/20100101 Firefox/106.0","version":"25.0.0.18"
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'instanceid' => 'my instance id',
'passwordsalt' => 'my passwordsalt',
'secret' => 'my secret',
'trusted_domains' =>
array (
0 => 'my host',
),
'datadirectory' => '/srv/http/nextcloud/data',
'dbtype' => 'mysql',
'version' => '25.0.0.18',
'overwrite.cli.url' => 'my Nextcloud instances domain name',
'dbname' => 'nextcloud',
'dbhost' => 'localhost',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'nextcloud',
'dbpassword' => 'my DB password',
'installed' => true,
'enable_previews' => false,
'default_phone_region' => 'US',
'memcache.local' => '\\OC\\Memcache\\APCu',
'memcache.distributed' => '\\OC\\Memcache\\Redis',
'memcache.locking' => '\\OC\\Memcache\\Redis',
'redis' =>
array (
'host' => '/run/redis/redis.sock',
'port' => '0',
'password' => 'my Redis password',
),
'maintenance' => false,
'theme' => '',
'loglevel' => 0,
'updater.secret' => 'my updater secret',
);
The output of your Apache/nginx/system log in /var/log/____:
2022/10/20 22:01:53 [error] 20572#20572: *57 FastCGI sent in stderr: "PHP message: PHP Fatal error: Uncaught Doctrine\DBAL\Exception: Failed to connect to the database: An exception occurred in the driver: SQLSTATE[HY000] [2002] No such file or directory in /srv/http/nextcloud/lib/private/DB/Connection.php:139