What is an inode?
Which file to edit to define which partition are mounted at startup?
Describe DNS

What are the TCP flags?
What are the HTTP headers?

What is the OSI model and what are the different layers?

Type of firewall and difference between stateful and stateless

What is ARP and how it is used

Which layer is living a hub, a switch, a router

What is a network, what defines a network.
What are the private IP addresses range

Difference between TCP and UDP?

Difference between ext2 and ext3?
What is file journalisation?