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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, 18.0.2): 17.0.2 Stable
Operating system and version (eg, Ubuntu 20.04): 20.04
Apache or nginx version (eg, Apache 2.4.25): 2.4.41
PHP version (eg, 7.1): 7.2.31-1
The issue you are facing:
Nextcloud not talking to Database after DB migration
Is this the first time you’ve seen this error? (Y/N):
Yes
Steps to replicate it:
(I have 1 Web server, and a whole other DB server. these are on different IPs)
- Stopped Apache2 to ensure nothing new written to DB on Webserver
- Mysql Dump on Database Server
- Scp the .sql dump onto Webserver
- Installed mysql-server and all dependencies required for mysql activities onto webserver
- adjusted config.php to match the new IP (localhost)
- Imported nextcloud db
- created mysql user matching the config.php expected values
- Granted (to be safe) ALL privileges on whole of Mysql to this user
- Flushed privileges
- Restarted apache2
- Accessed Same Webserver IP as always -> 500 error.
The output of your Nextcloud log in Admin > Logging:
No logs are being generated
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
<?php
$CONFIG = array (
'log_type' => 'syslog',
'logfile' => '',
'syslog_tag' => 'Nextcloud',
'loglevel' => '0',
'logdateformat' => 'F d, Y H:i:s',
'instanceid' => 'xxxxxxx',
'passwordsalt' => 'xxxxxxx',
'secret' => 'xxxxxxx',
'trusted_domains' =>
array (
0 => 'xxxxxxx',
1 => 'xxxxxxx',
),
'datadirectory' => '/var/www/html/data',
'dbtype' => 'mysql',
'version' => '17.0.2.1',
'overwrite.cli.url' => 'http://xxxx',
'dbname' => 'xxxxxxxx',
'dbhost' => 'localhost:3306', <--- The reason for the port here, is the webserver used to have "dbip:port" here, which always worked. (Old was 192.167.xxxx:2400) should you wonder.
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'oc_xxxxxxxx',
'dbpassword' => 'xxxxxxxxxx',
'installed' => true,
'has_internet_connection' => true,
'enable_previews' => true,
'debug' => true,
'enabledPreviewProviders' =>
array (
0 => 'OC\\Preview\\MP3',
1 => 'OC\\Preview\\MP4',
2 => 'OC\\Preview\\AVI',
3 => 'OC\\Preview\\PDF',
4 => 'OC\\Preview\\MKV',
5 => 'OC\\Preview\\Movie',
6 => 'OC\\Preview\\PDF',
7 => 'OC\\Preview\\Image',
8 => 'OC\\Preview\\JPG',
9 => 'OC\\Preview\\JPEG',
10 => 'OC\\Preview\\PNG',
),
'maintenance' => false,
);
The output of your Apache/nginx/system log in /var/log/____:
All I got to offer here is the below type errors.
192.168.1.100 - - [18/Nov/2020:14:19:16 +0000] "GET / HTTP/1.1" 500 477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.111 Safari/537.36"
If I revert the changes in config.php back to the database server ip:port and restart apache2 it works immediately, Login page arrives and its usable.
Please also note that I have tried the new db user + its password locally on the webserver to see if it could access the nextcloud db inside mysql locally - worked fine. Unfortunately I struggle to debug this as there are no logs coming out what so ever when pointing at the new “local” mysql server within the webserver.
I welcome any and all guidance and advise, and I have backups of the whole db from the database server (its still alive) so I can easily drop the db on the webserver and re-import if needed.
I am no expert, but something tells me there is a mismatch between the DB that the database server had, and what is being imported into mysql server on the webserver. Either utf8 character settings or something.
I did follow this guide;
So after install on webserver, I DID create an empty db with the same name + the whole “CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci” on the end
I did this step as my config.php says something about ‘mysql.utf8mb4’ => true,.
Please help.