I’m trying to install Nextcloud and MariaDB on a Synology DS420+ with DSM 7 using Docker and can’t get any further. First, Nextcloud should only be accessible in the LAN and later via VPN. Apparently I succeeded in installing MariaDB, creating a database with users and installing Nextcloud - at least there were no error messages. The maridadb directory is also not empty and /docker/mariaDB/nextcloudDB/db.opt exists. But I can’t get past the create admin account screen of Nextcloud.
Error while trying to create admin user: Failed to connect to the database: An exception occurred in the driver: SQLSTATE[HY000]  No such file or directory
Could it be the permissions for /docker?
What should the ownership/rights of /docker be? In my case only members of administrtors have rw access.
I created the directories for MariaDB and Nextcloud sometimes via the Synology File Station and sometimes via the volume dialogue in Docker. The Nextcloud directories belong to user 33 and group root, the MariaDB directories to user 999 and group users. However, according to the control panel, neither user 33 nor 999 exist. Where do users 33 and 999 come from?
I would like to have a user only for Docker (and thus Nextcloud and MariaDB), how do I do that?
Does anyone know better/clearer instructions for installing Nextcloud (and MariaDB) with Docker?