Expected behaviour I want to download, upload and synchronized my files from many PC with my ownCLoud server.
Actual behaviour Hi! I use ownCloud(8.2.7) with Mysql. I had some problems with connection to DB. All worked fine, but in one moment in admin panel, ownCloud offered to install ownCloud and choose DB, i choose Mysql and my admin acc/pass. But i've got system message like "Account is already exist", ok i created new admin account. Than i deleted "new" admin account and relogin with my base admin account. After this, my PC App dont work with server. And i cant to download any file frome web-version. I reconnect ownCloud to Mysql, after that i have problems with downloading files from server. I see all folders and files in my Admin panel, but i cant download it. I have error: "File not found" or "No such file or directory".
When the install screen appears, the config-file is not found any more. Did you put this on a different disk which was perhaps unmounted (can happen on USB drives)? Would be good to find the reason in case it happens again.
Concerning your error, you should run a filescan over the data folder (check before that it is not empty): sudo -u www-data php /var/www/owncloud/occ files:scan --all
With sudo -u www-data command, you run the command as if you were user www-data. Sure, you could run it as root as well. But, ownCloud itself runs with the permissions of www-data, so you have to make the home storage writable for www-data. If you don't want that, you can also mount this storage as external storage via SFTP which requires you in the OC interface to put the user's credentials.