What Linux is and why security teams use it
You tell the kernel from the distribution, work out the running system’s identity, look through the kernel’s windows /proc and /sys, see processes and the "everything is a file" idea, measure with capabilities that even root is limited inside a container, and at the end write the server’s profile and find a quietly running service yourself.
Level 101 · 40 min
Welcome to Northwind Logistics’ security team. On your first day team lead Daniel gives you a server and asks one question: "What exactly is this machine? What runs on it?" The first lesson of this course teaches you to answer that.
Most of the world’s servers, cloud machines, network devices and containers run Linux. That is why attackers and defenders both know Linux: Kali Linux is a Linux full of penetration testing tools, and security monitoring systems (SIEM, IDS) mostly run on Linux.
Analogy: think of a computer as a car. The kernel is the engine: it manages the hardware and hands out processor time and memory to programs in turn. The distribution (Kali, Ubuntu, Debian…) is the maker that puts seats, a steering wheel and a radio around the engine: it chooses the tools, the package system and the settings. They all use the same Linux engine.
In this lesson you try everything on the real Kali machine beside you. In the first steps the commands are ready ("Type in terminal"), then you type them by hand, and at the end you only see the goal.
What you will do in this lesson
- The engine: the kernel and uname
- The maker: the distribution
- The kernel’s window: /proc
- Processes: running programs
- Everything is a file: /dev
- Root in a container: capabilities
- The server profile
- The hidden service
- Short quiz
Skills you will earn
- Seeing the kernel version with uname
- Identifying the distribution with /etc/os-release
- Reading from the kernel and processes through /proc
- Listing running processes (ps aux)
- Knowing device files (/dev/null, /dev/urandom)
- Reading root’s capabilities in a container (CapEff, capsh)
- Redirecting output to a file with > and >>
Linux fundamentals · The terminal and the shell: your first commands →
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