Hello!
tl;dr - i was messin around with the wrong tmp directory; on the shared hosting enviroment each website(user) gets its own tmp folder.. and this had somehow ended up being owned by root!
I finally managed to get the upgrade from debian 7 to debian 8 working. So the server is up and running again.
Thats the output of apachectl Output of apachectl -V
apachectl -V
AH00548: NameVirtualHost has no effect and will be removed in the next release /etc/apache2/sites-enabled/000-ispconfig.conf:69
Server version: Apache/2.4.10 (Debian)
Server built: Sep 15 2016 20:44:43
Server's Module Magic Number: 20120211:37
Server loaded: APR 1.5.1, APR-UTIL 1.5.4
Compiled using: APR 1.5.1, APR-UTIL 1.5.4
Architecture: 64-bit
Server MPM: prefork
threaded: no
forked: yes (variable process count)
Server compiled with....
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=256
-D HTTPD_ROOT="/etc/apache2"
-D SUEXEC_BIN="/usr/lib/apache2/suexec"
-D DEFAULT_PIDLOG="/var/run/apache2.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="mime.types"
-D SERVER_CONFIG_FILE="apache2.conf"php stuff that is installed aka dpkg -l | grep php
dpkg -l | grep php
ii libapache2-mod-php5 5.6.27+dfsg-0+deb8u1 amd64 server-side, HTML-embedded scripting language (Apache 2 module)
ii php-auth 1.6.4-1 all Creating an authentication system
ii php-auth-sasl 1.0.6-1+deb8u1 all Abstraction of various SASL mechanism responses
ii php-db 1.7.14-3 all PHP PEAR Database Abstraction Layer
ii php-gettext 1.0.11-1 all read gettext MO files directly, without requiring anything other than PHP
ii php-http-request 1.4.4-4 all PEAR class to provide an easy way to perform HTTP requests
ii php-log 1.12.8-2 all Logging Framework
ii php-mail 1.2.0-7 all Class that provides multiple interfaces for sending emails
ii php-mail-mime 1.8.9-1+deb8u1 all PHP PEAR module for creating MIME messages
ii php-mdb2 2.5.0b5-1 all merge of the PEAR DB and Metabase php database abstraction layers
ii php-net-dime 1.0.2-2 all class that implements DIME encoding
ii php-net-smtp 1.6.2-2 all PHP PEAR module implementing SMTP protocol
ii php-net-socket 1.0.14-1 all PHP PEAR Network Socket Interface module
ii php-net-url 1.0.15-3 all easy parsing of Urls
ii php-pear 5.6.27+dfsg-0+deb8u1 all PEAR - PHP Extension and Application Repository
ii php-soap 0.13.0-1 all SOAP Client/Server class for PHP
ii php-tcpdf 6.0.093+dfsg-1 all PHP class for generating PDF files on-the-fly
ii php5 5.6.27+dfsg-0+deb8u1 all server-side, HTML-embedded scripting language (metapackage)
ii php5-cgi 5.6.27+dfsg-0+deb8u1 amd64 server-side, HTML-embedded scripting language (CGI binary)
ii php5-cli 5.6.27+dfsg-0+deb8u1 amd64 command-line interpreter for the php5 scripting language
ii php5-common 5.6.27+dfsg-0+deb8u1 amd64 Common files for packages built from the php5 source
ii php5-curl 5.6.27+dfsg-0+deb8u1 amd64 CURL module for php5
ii php5-fpm 5.6.27+dfsg-0+deb8u1 amd64 server-side, HTML-embedded scripting language (FPM-CGI binary)
ii php5-gd 5.6.27+dfsg-0+deb8u1 amd64 GD module for php5
ii php5-imagick 3.2.0~rc1-1 amd64 Provides a wrapper to the ImageMagick library
ii php5-imap 5.6.27+dfsg-0+deb8u1 amd64 IMAP module for php5
ii php5-intl 5.6.27+dfsg-0+deb8u1 amd64 internationalisation module for php5
ii php5-json 1.3.6-1 amd64 JSON module for php5
ii php5-mcrypt 5.6.27+dfsg-0+deb8u1 amd64 MCrypt module for php5
ii php5-memcache 3.0.8-5 amd64 memcache extension module for PHP5
ii php5-memcached 2.2.0-2 amd64 memcached extension module for PHP5, uses libmemcached
ii php5-mysql 5.6.27+dfsg-0+deb8u1 amd64 MySQL module for php5
ii php5-pspell 5.6.27+dfsg-0+deb8u1 amd64 pspell module for php5
ii php5-readline 5.6.27+dfsg-0+deb8u1 amd64 Readline module for php5
ii php5-recode 5.6.27+dfsg-0+deb8u1 amd64 recode module for php5
ii php5-sqlite 5.6.27+dfsg-0+deb8u1 amd64 SQLite module for php5
ii php5-tidy 5.6.27+dfsg-0+deb8u1 amd64 tidy module for php5
ii php5-xcache 3.2.0-1 amd64 Fast, stable PHP opcode cacher
ii php5-xmlrpc 5.6.27+dfsg-0+deb8u1 amd64 XML-RPC module for php5
ii php5-xsl 5.6.27+dfsg-0+deb8u1 amd64 XSL module for php5
ii phpmyadmin 4:4.2.12-2+deb8u2 all MySQL web administration toolBut now nextcloud (fork of owncloud, and owncloud itself) wont allow users to login through the web app (aka PHP frontend). You get the site displayed, the login-mask is there, you type in your credentials and it loads.. and throws you back to the login-page again.
The Apache logfiles themselves do not give any insightfull information, but the nextcloud.log file has some wired stuff about a tmp directory not there, which makes to me and google no sense:
the awefull output of owncloud
tail -f nextcloud.log
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): open(\/var\/www\/clients\/client3\/web1\/tmp\/sess_60gtqr9uekvm2cdiuursf9e2t3, O_RDWR) failed: Permission denied (13) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"jfIs4p+yNIKBNfeniyi9","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (\/var\/www\/clients\/client3\/web1\/tmp) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:27+00:00","method":"POST","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): open(\/var\/www\/clients\/client3\/web1\/tmp\/sess_rbcotmj3jcgk6010g8kgu7e0d4, O_RDWR) failed: Permission denied (13) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"eBu7kKhu79U4sbMxCZZp","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (\/var\/www\/clients\/client3\/web1\/tmp) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/apps\/files\/","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:27+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): open(\/var\/www\/clients\/client3\/web1\/tmp\/sess_jjkstu3e3k5r0d02896l0785k1, O_RDWR) failed: Permission denied (13) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"sj\/YmPC2kc4fKsq3Aduh","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (\/var\/www\/clients\/client3\/web1\/tmp) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/login?redirect_url=%252Fnextcloud%252Findex.php%252Fapps%252Ffiles%252F","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): open(\/var\/www\/clients\/client3\/web1\/tmp\/sess_h6t0dcbs3uvdfa0qgjrc80aat4, O_RDWR) failed: Permission denied (13) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"Io+Gr2thjSXjU7xnkVRT","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (\/var\/www\/clients\/client3\/web1\/tmp) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/index.php\/core\/js\/oc.js?v=f7d8f04619ecde140e312049aae6c158","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"no app in context","message":"Temporary directory \/var\/www\/clients\/client3\/web1\/tmp is not present or writable","level":2,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): open(\/var\/www\/clients\/client3\/web1\/tmp\/sess_ut8tus25tooun6p9tj002cgtm1, O_RDWR) failed: Permission denied (13) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}
{"reqId":"K07biDpj76dJUESEKcUg","remoteAddr":"82.218.xxx.xxx","app":"PHP","message":"session_write_close(): Failed to write session data (files). Please verify that the current setting of session.save_path is correct (\/var\/www\/clients\/client3\/web1\/tmp) at \/var\/www\/clients\/client3\/web1\/web\/nextcloud\/lib\/private\/Session\/Internal.php#104","level":3,"time":"2016-11-09T11:46:28+00:00","method":"GET","url":"\/nextcloud\/cron.php","user":"--"}I will keep digging, but by now my brain is a little bit locked on that issue, and the migration brought a view other hickups (yeah incompatible config markup changes in so many corners of debian 8) so I hope that you guys and galls can help me.