Multiple instances on same server and updating

Hi, I installed OC as recommended for Ubuntu 16.04.

apt-get install owncloud-files

To install another instance, I thought of renaming the directory in /var/www and doing the install again. This might work, but I am wondering how to update the renamed package via apt.

Many thanks

I follow now the custom installation path. It seems to be better fitting.
https://doc.owncloud.org/server/latest/admin_manual/installation/source_installation.html