Package Management on Linux, FreeBSD, and Other UNIX-Family OSes

System administrators must manage software packages. With a mix of Unix-family operating systems, you must use the commands specific to each platform. On Red-Hat-derived systems, these include rpm, dnf (formerly yum), and urpmi. On Debian derivatives such as the many Ubuntu variants, these include apt and dpkg. On FreeBSD, one command pkg does it all. On OpenBSD, it's a family of commands starting pkg_*, and on Solaris, similarly named pkg*. Here are explanations through examples of how to manage software packages and answer questions about installed or missing software using these commands across all those operating systems.