what is the difference between yum and dnf
DNF (software) DNF or Dandified YUM[2][3][4] is the next-generation version of the Yellowdog Updater, Modified (yum), a package manager for .rpm-based distributions. DNF was introduced in Fedora 18,[5] and it has been the default package manager for Fedora since version 22.[6]
DMZ (computing) In computer security, a DMZ or demilitarized zone (sometimes referred to as a perimeter network) is a physical or logical subnetwork that contains and exposes an organization's external-facing services to an untrusted network, usually a larger network such as the Internet. The purpose of a DMZ is to add an additional layer of security to an organization's local area network (LAN): an external network node can access only what is exposed in the DMZ, while the rest of the organization's network is firewalled. The DMZ functions as a small, isolated network positioned between the Internet and the private network and, if its design is effective, allows the organization extra time to detect and address breaches before they would further penetrate into the internal networks.