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Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can 
Nextcloud version (eg, 18.0.2): 18.0.3
Operating system and version (eg, Ubuntu 20.04):Debian GNU/Linux 10 (buster)
Apache or nginx version (eg, Apache 2.4.25): apache2 2.4.38-3+deb10u3
PHP version (eg, 7.1):php7.3
The issue you are facing:
When I try to update to 18.0.4 via the gui updater I get this error after clicking on start update (in one huge block with red background):
(Loooooots of lines removed because of forum restrictions)
Check for expected files
Parsing response failed. <!DOCTYPE html> <html class="ng-csp" data-placeholder-focus="false" lang="de" data-locale="de" > <head data-user="admin" data-user-displayname="admin" data-requesttoken="lNGXNxsh1vTQG4Ve5J73ytgSYgGRXEieBH8LBSl+XTM=:7ZClenpUpKCaUvMbnaevi5QkMGTrBBrJMEhxLngRO2A="> <meta charset="utf-8"> <title> Dateien - Unsere Wolke </title> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0"> <meta name="apple-itunes-app" content="app-id=1125420102"> <meta name="apple-mobile-web-app-capable" content="yes"> <meta name="apple-mobile-web-app-status-bar-style" content="black"> <meta name="apple-mobile-web-app-title" content="Unsere Wolke"> <meta name="mobile-web-app-capable" content="yes"> <meta name="theme-color" content="#0082c9"> <link rel="icon" href="/index.php/apps/theming/favicon/files?v=5"> <link rel="apple-touch-icon" href="/index.php/apps/theming/icon/files?v=5"> <link rel="mask-icon" sizes="any" href="/core/img/favicon-mask.svg" color="#0082c9"> <link rel="manifest" href="/index.php/apps/theming/manifest?v=5"> <link rel="stylesheet" href="/index.php/css/core/1090-d59b-server.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/index.php/css/core/1090-d59b-css-variables.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/apps/files_pdfviewer/css/style.css?v=6a154fe0-5"> <link rel="stylesheet" href="/index.php/css/notifications/783c-d59b-styles.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/index.php/css/core/1090-d59b-results.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/index.php/css/files/9eeb-d59b-merged.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/apps/audioplayer/css/3rdparty/fontello/css/fontello.css?v=fcc9a5d9-5"> <link rel="stylesheet" href="/apps/files_rightclick/css/app.css?v=5e585c9e-5"> <link rel="stylesheet" href="/index.php/css/files_sharing/c5f2-d59b-icons.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/index.php/css/activity/6c1e-d59b-style.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/index.php/css/spreed/ecfa-d59b-merged-files.css?v=7b9d070c124c08774441c2c7dfbc9418-82869653-5"> <link rel="stylesheet" href="/apps/files_external/css/external.css?v=d16b8f0e-5"> <script nonce="bE5HWE54c2gxdlRRRzRWZTVKNzN5dGdTWWdHUlhFaWVCSDhMQlNsK1hUTT06N1pDbGVucFVwS0NhVXZNYm5hZXZpNVFrTUdUckJCckpNRWh4TG5nUk8yQT0=" defer src="/core/js/dist/main.js?v=82869653-5"></script> <script nonce="bE5HWE54c2gxdlRRRzRWZTVKNzN5dGdTWWdHUlhFaWVCSDhMQlNsK1hUTT06N1pDbGVucFVwS0NhVXZNYm5hZXZpNVFrTUdUckJCckpNRWh4TG5nUk8yQT0=" defer src="/index.php/js/core/merged-template-prepend.js?v=82869653-5"></script> <script nonce="bE5HWE54c2gxdlRRRzRWZTVKNzN5dGdTWWdHUlhFaWVCSDhMQlNsK1hUTT06N1pDbGVucFVwS0NhVXZNYm5hZXZpNVFrTUdUckJCckpNRWh4TG5nUk8yQT0=" defer src="/core/search/js/search.js?v=82869653-5"></script> <script nonce="bE5HWE54c2gxdlRRRzRWZTVKNzN5dGdTWWdHUlhFaWVCSDhMQlNsK1hUTT06N1pDbGVu
</body> </html>
Is this the first time you’ve seen this error? (Y/N):Y
Steps to replicate it:
Have Nextcloud installed behind a reverse proxy with this setup:
<?php
$CONFIG = array (
'instanceid' => '...',
'passwordsalt' => '...',
'secret' => '...',
'trusted_domains' =>
array (
0 => 'zem',
1 => 'zem.vpn',
2 => 'nuvola.the-grue.de',
),
'datadirectory' => '/srv/nuvola',
'dbtype' => 'mysql',
'version' => '18.0.3.0',
'overwrite.cli.url' => 'http://nuvola.the-grue.de',
'dbname' => 'nextcloud_nuvola',
'dbhost' => 'localhost',
'dbport' => '',
'dbtableprefix' => 'oc_',
'mysql.utf8mb4' => true,
'dbuser' => 'nextcloud_nuvola_admin',
'dbpassword' => '...',
'installed' => true,
'maintenance' => false,
'theme' => '',
'loglevel' => 2,
'trusted_proxies' =>
array (
0 => '192.168.178.0/24',
1 => '192.168.23.0/24',
),
'overwritehost' => 'nuvola.the-grue.de',
'overwriteprotocol' => 'https',
'overwritewebroot' => '/',
'overwritecondaddr' => '^192\\.168\\.23\\.1$',
'mail_smtpmode' => 'sendmail',
'mail_sendmailmode' => 'pipe',
'mail_from_address' => 'markus',
'mail_domain' => 'the-grue.de',
'mail_smtpsecure' => 'ssl',
'memcache.local' => '\\OC\\Memcache\\APCu',
'memcache.distributed' => '\\OC\\Memcache\\Redis',
'redis' =>
array (
'host' => '/var/run/redis/redis-server.sock',
'port' => 0,
'dbindex' => 0,
'timeout' => 1.5,
),
'updater.secret' => '...',
);
Then start the update in the web gui.
The output of your Nextcloud log in Admin > Logging:
Only some errors of the mail app.
The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):
see above
The output of your Apache/nginx/system log in /var/log/____:
zem:80 192.168.23.1 - - [30/Apr/2020:22:20:21 +0200] "POST /nuvola/nuvola/updater/index.php HTTP/1.1" 302 941 "https://nuvola.the-grue.de/updater/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.92 Safari/537.36"
zem:80 192.168.23.1 - - [30/Apr/2020:22:20:21 +0200] "GET /nuvola/index.php/apps/files/ HTTP/1.1" 200 10111 "https://nuvola.the-grue.de/updater/" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.92 Safari/537.36"
[Thu Apr 30 22:21:38.330828 2020] [core:info] [pid 11639] [client 192.168.23.1:41284] AH00128: File does not exist: /srv/www/nuvola/htdocs/nuvola/updater/index.php, referer: https://nuvola.the-grue.de/updater/