First, you should have a look  at this tutorial:

https://panovski.me/install-odoo-8-on-centos-7/

it was written for Odoo 8 and Postgresql 9.3, but you can do the same to install Odoo 9 and later Postgres (note that you need to change git command to clone source code from branch 9.0).

Then when you are familiar with that, you may find it is easy to "clone" an instance of Odoo to another one.

Just copy and paste source code (command cp -r in linux) and modify the path, e.g:

ExecStart=/home/odoo/odoo/bin/python /opt/odoo/openerp-server --config=/etc/odoo-server.conf

to

ExecStart=/home/odoo/odoo/bin/python /opt/odoo2/openerp-server --config=/etc/odoo-server2.conf

(this case, I use the same Python Virtual Environment in  /home/odoo/odoo/bin/python)

And also change port number in configuration file. Spend some time to consume https://www.odoo.com/documentation/9.0/reference/cmdline.html to under stand xmlrpc port and db filter parameters

This way you can deploy serveral Odoo instance on one server.

If you want to deploy all instances using port 80, you should use nginx as proxy.

Take a look in documentation.

And especially the part --db-filter

https://www.odoo.com/documentation/9.0/setup/deploy.html