How might I compare two installations?

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http://askubuntu.com – Our office is using a Proxmox Virtual Environment (v. 1.9) to run servers. It is capable of running either OpenVZ templates or full KVM installations. After an initial attempt and failure to successfully install software for evaluation in an Ubuntu 12.04 server running as an OpenVZ container, I decided to try installing it in a "normal" server installation in VirtualBox on my laptop. This time, the software worked – with only an adjustment to the firewall (ufw). Yet the OpenVZ container doesn't even have this package. This discovery leads me to believe that it would be helpful to know (or d (HowTos)