Configuration files
Structure and contents of /etc/passwd, /etc/shadow, /etc/group, /etc/gshadow, /etc/login.defs, /etc/securetty, /etc/security/access.conf, /etc/security/limits.conf, /etc/security/pwquality.conf, .profile, .bash_profile, .bashrc, etc.
 
User administration commands
Syntax and options of useradd, usermod, groupadd, groupmod, passwd, chage, newusers, chpasswd, newgrp, groupmems, gpasswd, etc.
 
setuid, setgid & sticky bit
What are the special permissions for and how to use them.
 
su command
What is “su” and how to use it.
 
sudo command
What is “sudo” and how to use it.
 
Access Control Lists
What are ACLs for and how to use them.
 
Pluggable Authentication Modules
What are PAMs used for and how to configure them.