12.3. Going Further
This book taught you a lot of things that any Kali Linux user should know, but we made some hard choices to keep it short, and there are many topics that were not covered.
If you want to learn more about system administration, then we can only recommend that you check out the Debian Administrator's Handbook:
You will find there many supplementary chapters covering common Unix services that we have entirely skipped in this book. And even for chapters that have been reused in the Kali book, you will find plenty of supplementary tips, notably on the packaging system (which is also covered more extensively at its lowest level).
The Debian book obviously presents more deeply the Debian community and the way it is organized. While this knowledge is not vital, it is really useful when you have to interact with Debian contributors, for example through bug reports.
You probably noticed by now that this book did not teach you penetration testing. But the things you learned are still important. You are now ready to fully exploit the power of Kali Linux, the best penetration testing framework. And you have the basic Linux skills required to participate in Offensive Security's training.
If you feel that you are not yet ready for a paid course, you can start by following the Metasploit Unleashed free online training. Metasploit is a very popular penetration testing tool and you have to know it if you are serious about your plans to learn penetration testing.
The next logical step would then be to follow the Penetration Testing with Kali Linux online course leading the path to the famous "Offensive Security Certified Professional" certification. This online course can be followed at your own pace but the certification is actually a difficult, 24h long, real-word, hands-on penetration test which takes place in an isolated VPN network.
Are you up to the challenge?