Linux: file and permission commands (ls, cp, mv, rm, chmod, chown, sudo, su), package managers (apt, dnf), ip, df, top, ps, grep, find, man, key files (/etc/passwd, /etc/shadow, /etc/hosts, /etc/fstab, /etc/resolv.conf)

Linux is managed mostly from a shell such as bash. Commands are case-sensitive, paths use forward slashes and there are no drive letters: everything hangs off the root directory /, and other disks are mounted into that tree. When in doubt, read the manual page with man, as in man chmod, and press q to quit. The A+ exam expects you to recognize the core commands, read a permission string and know which configuration file does what.