Installation nextcloud 13.0.1 postgresql

https://wolke.systron.de/index.php zeigt

Internal Server Error
The server encountered an internal error and was unable to complete your request.
Please contact the server administrator if this error reappears multiple times, please include the technical details below in your report.
More details can be found in the server log.

nextcloud.log:
Next Doctrine\DBAL\Driver\PDOException: SQLSTATE[42P01]: Undefined table: 7 FEHLER: Relation »oc_appconfig« existiert nicht
LINE 1: SELECT * FROM “oc_appconfig”

debian stretch aktuell
lxc
php 7.0
php -m
[PHP Modules]
bz2 calendar Core ctype curl date dom exif fileinfo filter ftp gd gettext hash iconv igbinary imagick intl json libxml mbstring mcrypt mysqli mysqlnd openssl pcntl pcre PDO pdo_mysql pdo_pgsql pgsql Phar posix readline redis Reflection session shmop SimpleXML sockets SPL standard sysvmsg sysvsem sysvshm tokenizer wddx xml xmlreader xmlwriter xsl Zend OPcache zip zlib

$CONFIG = array (
  'instanceid' => '',
  'passwordsalt' => '',
  'secret' => '',
  'trusted_domains' => 
  array (
    0 => 'wolke.systron.de',
    1 => '10.0.0.10',
  ),
  'datadirectory' => '/data',
  'dbtype' => 'pgsql',
  'version' => '',
  'dbname' => 'nextcloud',
  'dbhost' => 'postgresql-host',
  'dbport' => '5432',
  'dbtableprefix' => 'oc_',
  'dbuser' => 'nextcloud',
  'dbpassword' => 'XXXXXXXXX',
  'installed' => true,
  'default_language' => 'de',
  'force_language' => 'de',
  'memcache.local' => '\OC\Memcache\Redis',
  'redis' => array(
       'host' => '/var/run/redis/redis.sock',
       'port' => 0,
       ),
  'memcache.locking' => '\OC\Memcache\Redis',
  'mail_from_address' => 'root',
  'mail_smtpmode' => 'php',
  'mail_smtpauthtype' => 'PLAIN',
  'maintenance' => false,
  'theme' => '',
  'loglevel' => 0,

Does oc_appconfig actually exist? Did the installation yield any error messages?

find nextcloud/ | grep -i oc_appconfig

nothing found

No error messages

oc_appconfig should be a table in the nextcloud database, not a file/directory. Afaik, it is created during installation, then Nextcloud is creating the database and its tables. Are you sure you are using an external database server? If not, postgresql-host probably should be localhost.

You should check your logs when the installation was done or maybe run the installation again and monitor logs or error messages. I guess something went wrong when accessing the database.

Apr 21 14:26:05 postgres postgres[17409]: [4-1] 2018-04-21 12:26:05 GMT
LOG: Verbindung autorisiert: Benutzer=nextcloud Datenbank=nextcloud SSL
an (Protokoll=TLSv1.2,
VerschlĂŒsselungsmethode=ECDHE-RSA-AES256-GCM-SHA384, Komprimierung=aus)
Apr 21 14:26:05 postgres postgres[17409]: [5-1] 2018-04-21 12:26:05 GMT
FEHLER: Relation »oc_appconfig« existiert nicht bei Zeichen 15

Problem solved. Old configfile config.php must realy empty for a new installation.