Users typically use simple passwords. This is what computer attackers use. They calculate the password necessary for penetrating the network by selection.
Alison Chaiken has shared an article ‘Analyzing the Linux boot process’.
The article can help you understand how to the systems work and it is great preparation for dealing with the inevitable failures.
It’s hard work to monitor and debug performance problems with Linux. If you have the right tools, then it will be easier to work. This presentation describes a list of Linux monitoring tools on the Internet.