Earlier I have tried ownCloud with the VM provided at https://owncloud.org/install/#edition. Today I setup the development environment on Ubuntu 16.04 and was able to run ownCloud successfully by building the source. Then I started integrating Dropbox with ownCloud following the link provided by @PVince81. After granting access to the ownCloud from the Dropbox following error occurred.
Transactional file locking should be configured to use memory-based locking, not the default slow database-based locking. See the documentation ↗ for more information.
You are accessing this site via HTTP. We strongly suggest you configure your server to require using HTTPS instead as described in our security tips.
Then I followed ownCloud Documentation Overview to enable HTTPS for ownCloud. But I cannot understand the method mentioned in Enable HTTP Strict Transport Security. Where do I have to enter
<IfModule mod_headers.c>
Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains"
</IfModule>
lines. Do I have to edit the /etc/apache2/sites-available/default-ssl.conf? But that file contains a <VirtualHost _default_:443> entry but not a <VirtualHost *:443> entry as mentioned in the above link. Can anyone please help me to solve this issue?