WARN Piwik\Session[2017-12-15 12:06:39] [4096c] Unable to start session: session has already been started by session.auto-start or session_start()
Piwik › Error
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Error: Unable to start session. Please check that the web server has enough permission to write to these files/directories:
For example, on a Linux server if your Apache httpd user is www-data, you can try to execute:
chown -R www-data:www-data /var/www/web0/html/gesine-imhof.dev/piwik/tmp/sessions/
chmod -R 0755 /var/www/web0/html/gesine-imhof.dev/piwik/tmp/sessions/

If you still experience issues after trying these changes, we recommend that you enable database session storage.

Debug: the original error was 
session has already been started by session.auto-start or session_start()

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