Hello Coffee_is_life, hello Mike,
your tip helped!
However, I had to take a few extra steps to get everything going again. After stopping mariadb and changing the datadir, I had to execute the following commands so that mariadb could be restarted:
First, I had to reinstall the system tables. For this I had to execute the following command:
mysql_install_db --user=mysql
Since I run my mail server on Debian, I had to grant rights to a system user with the following commands after starting mariadb:
mysql -uroot -p
mysql> grant all privileges on *.* to 'debian-sys-maint'@'localhost' identified by '<Password>' with grant option;
The password to be assigned here can be found in the file /etc/mysql/debian.cnf.
I have also recreated the kopano database user and authorized it with:
mysql> create user 'kopano'@'%' identified by '<Password>';
mysql> grant all privileges on *.* to 'kopano'@'%' identified by '<Password>' with grant option;
mysql> exit
Then mariadb had to be restarted.
Then I had to set the password for the root user with:
mysqladmin -u root password <new Password>
Now I could create a new empty database and import the dump.
After the import the Kopano server was restarted correctly. Access is now possible again.
Now everything works as it should. :smiley:
Thanks for your support. I would not have done without you!