Nextcloud update reset all settings and user account is removed

Nextcloud version: 13.0.7
Operating system and version: Raspian 8.0 jessie
Apache or nginx version: Apache/2.4.10 (Raspbian)
PHP version: PHP 5.6.38-0+deb8u

I am running nextcloud on my Raspberry Pi. I just updated it to version 13.0.7 using the updater on the web interface. It seemed to failed and I was redirected to the login screen, where it said «create administrator account».
I tried to log in with my usual username and password but now all my files, settings and calendars etc. are gone as if I am on a new account.

In the settings it does not list a different user but the new one.

I used to have my files on a external disk with path /mnt/usbdrive/ncdata/niklassc/files and it seems like those files are still there. The new ones are created in /var/www/nextcloud/data/niklassc/files/. However, I don’t really know where my calendar, contacts etc. are.

When I used the updater it said in one step that it is doing some backups. Is it possible to revert the update to get to the state before the update or do I have to try to find my files and settings somehow?

If the latter is the case, does anyone know how I can get my calendar and contact files?

Is this the first time you’ve seen this error? (Y/N): Y

The output of your Nextcloud log in Admin > Logging:

The log on the web interface is empty

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

 <?php
 $CONFIG = array (
   'instanceid' => '[...]',
   'passwordsalt' => '[...]',
   'secret' => '[...]',
   'trusted_domains' =>
   array (
     0 => 'rpi2',
   ),
   'datadirectory' => '/var/www/nextcloud/data',
   'overwrite.cli.url' => 'https://rpi2',
   'dbtype' => 'sqlite3',
   'version' => '13.0.7.2',
   'installed' => true,
 )

I replaced some information here with […] because it seemed like possibly confidential information.

The output of your Apache/nginx/system log in /var/log/____:

$ ls /var/log/apache2
access.log        access.log.11.gz  access.log.14.gz  access.log.4.gz  access.log.7.gz  error.log        error.log.11.gz  error.log.14.gz  error.log.4.gz  error.log.7.gz  other_vhosts_access.log
access.log.1      access.log.12.gz  access.log.2.gz   access.log.5.gz  access.log.8.gz  error.log.1      error.log.12.gz  error.log.2.gz   error.log.5.gz  error.log.8.gz
access.log.10.gz  access.log.13.gz  access.log.3.gz   access.log.6.gz  access.log.9.gz  error.log.10.gz  error.log.13.gz  error.log.3.gz   error.log.6.gz  error.log.9.gz
$ cat /var/log/apache2/access.log

[...]
10.36.255.57 - - [13/Oct/2018:21:06:17 +0200] "GET /index.php/apps/logreader/poll?lastReqId=9v4120xUMeuBjTjlugz7 HTTP/1.1" 200 976 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:06:43 +0200] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 2312 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:06:55 +0200] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 2312 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:06:38 +0200] "GET /index.php/apps/logreader/poll?lastReqId=9v4120xUMeuBjTjlugz7 HTTP/1.1" 200 976 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:07:13 +0200] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 2312 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:06:59 +0200] "GET /index.php/apps/logreader/poll?lastReqId=9v4120xUMeuBjTjlugz7 HTTP/1.1" 200 976 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:07:25 +0200] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 2312 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:07:20 +0200] "GET /index.php/apps/logreader/poll?lastReqId=9v4120xUMeuBjTjlugz7 HTTP/1.1" 200 976 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0"
10.36.255.57 - - [13/Oct/2018:21:07:43 +0200] "GET /ocs/v2.php/apps/notifications/api/v2/notifications HTTP/1.1" 200 2312 "-" "Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:62.0) Gecko/20100101 Firefox/62.0

$ cat /var/log/apache2/access.log.1

[...]
10.36.255.28 - niklassc [13/Oct/2018:05:46:56 +0200] "PROPFIND /remote.php/dav/calendars/niklassc/uni/ HTTP/1.1" 207 3636 "-" "DAVdroid/2.0.4-ose (2018/09/10; dav4android; okhttp/3.11.0) Android/7.0"
10.36.255.28 - niklassc [13/Oct/2018:05:46:58 +0200] "PROPFIND /remote.php/dav/calendars/niklassc/eth_timetable_20180923ics/ HTTP/1.1" 207 4558 "-" "DAVdroid/2.0.4-ose (2018/09/10; dav4android; okhttp/3.11.0) Android/7.0"
::1 - - [13/Oct/2018:05:47:00 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:01 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:04 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:05 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:06 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:07 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
::1 - - [13/Oct/2018:05:47:08 +0200] "OPTIONS * HTTP/1.0" 200 128 "-" "Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t (internal dummy connection)"
10.36.255.28 - niklassc [13/Oct/2018:05:56:51 +0200] "GET /index.php/204 HTTP/1.1" 204 2581 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:05:56:52 +0200] "GET /index.php/204 HTTP/1.1" 204 1380 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:05:56:54 +0200] "GET /index.php/204 HTTP/1.1" 204 1378 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:06:00:06 +0200] "GET /index.php/204 HTTP/1.1" 204 1521 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:06:00:07 +0200] "GET /index.php/204 HTTP/1.1" 204 1384 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:06:16:51 +0200] "GET /index.php/204 HTTP/1.1" 204 2583 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:06:16:51 +0200] "GET /index.php/204 HTTP/1.1" 204 2581 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"
10.36.255.28 - niklassc [13/Oct/2018:06:16:53 +0200] "GET /index.php/204 HTTP/1.1" 204 1380 "-" "Mozilla/5.0 (Android) ownCloud-android/3.3.0"

$ cat /var/log/apache2/error.log

[Sat Oct 13 06:25:07.775298 2018] [ssl:warn] [pid 23927] AH01909: rpi2:443:0 server certificate does NOT include an ID which matches the server name
[Sat Oct 13 06:25:07.776838 2018] [mpm_prefork:notice] [pid 23927] AH00163: Apache/2.4.10 (Raspbian) OpenSSL/1.0.1t configured -- resuming normal operations
[Sat Oct 13 06:25:07.776926 2018] [core:notice] [pid 23927] AH00094: Command line: '/usr/sbin/apache2'
[Sat Oct 13 18:40:58.964840 2018] [:error] [pid 23069] [client 10.36.255.57:47648] PHP Fatal error:  Class 'OCA\\FederatedFileSharing\\AddressHandler' not found in /var/www/nextcloud/apps/federatedfilesharing/lib/AppInfo/Application.php on line 92
[Sat Oct 13 18:44:48.633397 2018] [:error] [pid 23066] [client 10.36.255.57:47720] PHP Notice:  Undefined index: datadirectory in /var/www/nextcloud/updater/index.php on line 283
[Sat Oct 13 18:53:14.504658 2018] [:error] [pid 23066] [client 10.36.255.57:48914] creating sqlite db
[Sat Oct 13 18:57:45.067380 2018] [authz_core:error] [pid 24714] [client 10.36.255.57:49022] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 18:58:28.602644 2018] [authz_core:error] [pid 23067] [client 10.36.255.57:49086] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 18:58:52.506685 2018] [authz_core:error] [pid 23067] [client 10.36.255.57:49142] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 19:17:48.137561 2018] [authz_core:error] [pid 24816] [client 10.36.255.57:50554] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 19:21:33.709458 2018] [authz_core:error] [pid 22428] [client 10.36.255.57:50702] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 19:24:56.053641 2018] [authz_core:error] [pid 23809] [client 10.36.255.57:50766] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 19:24:57.678998 2018] [authz_core:error] [pid 24714] [client 10.36.255.57:50772] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 20:51:01.868496 2018] [authz_core:error] [pid 25325] [client 10.36.255.57:51824] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 20:51:24.454879 2018] [authz_core:error] [pid 24714] [client 10.36.255.57:51852] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata
[Sat Oct 13 20:55:13.507751 2018] [authz_core:error] [pid 24708] [client 10.36.255.57:51926] AH01630: client denied by server configuration: /var/www/nextcloud/data/.ocdata

In this one it says at some point that it is creating a sqlite database. The server now also is using a a sqlite database but I’m quite sure that I was not using sqlite before the update broke.