 History.
 Difference Between Linux and Windows
 Difference Between Linux and Unix
 GNU
 Various Linux Distributions.
 Pros and Cons

Who/why/what is root

 mkdir
 touch
 ls
 pwd
 cd
 chmod
 df
 du
 dd
 adduser
 sort
 passwd
 rm/rmdir
 date
 tar
 gzip
 top

Vi Editor

 File Structure and hierarchy
 File Permissions
 LVM overview

 cron
 at

 RPM
 make

 route
 ifconfig
 ping
 netstat

 modprobe
 rmmod
 insmod
 lsmod
 modinfo

 ssh
 Sshd
 scp