1) Installing packages: with yum, from sources, with rpm

2) Runlevels, know how to change from one to another, know how to enter runlevel 1

3) Standalone and XINETD based Services: how to start (in the current session, starting 
after reboot),  stop, see status, test (for the xinetd based services - connect with 
telnet)

4) Kernel configuration: enabling drivers (USB1, USB3, PCMCIA, ...) and services (NFS, 
NIS, ...)

5)Network interface alias. The route command

6) DHCP server and client configuration

7) System monitoring: top, sar, ps, cacti, ...

8) Httpd configuration

9) Cron jobs configuration

10) yum repairing. Adding epel repository to yum

10) iptables configuration