It helps to use one of the more flexible and less user-friendly Linux distros on an old desktop or in a VM. I kind of like ArchLinux. The problem with Linux, t

It helps to use one of the more flexible and less user-friendly Linux distros on an old desktop or in a VM. I kind of like ArchLinux. The problem with Linux, though, is that there are several main families, and even distros in the same family don't really adhere to any specific standard. Some might use syslog, others syslog-ng. Some sendmail, others postfix. It's kind of a mess. Familiarizing yourself with a few flavors (and maybe FreeBSD or OpenBSD for good measure) on a machine you force yourself to use on occasion, you will find your comfort level for basic UNIX power-user and sysadmin stuff will grow.