Stop 02 · Linux & Command LineTopics · 1/11

Linux Fundamentals

In short

Most servers on the internet, and nearly every cloud machine and container, run Linux. If you can find your way around a Linux box, you can work on almost any server.

The dominant operating system for servers and cloud infrastructure — understanding its architecture, distributions, and basic philosophy ('everything is a file') is foundational for nearly everything else in DevOps.

The mascot sits at a desk piled with neatly tied office files, a keyboard and a hard disk among them.

Think of it like this

The sarkari office where everything is a file

In a government office, your complaint, your pension, even a broken fan becomes a file on someone's desk. Linux thinks the same way. Documents, hard disks, your keyboard, even running programs show up as files you can open and read.

Watch it happen

The layers of a Linux system

Hardware

Kernel

Shell (bash)

systemd

ls, grep, git

nginx, sshd

1/4At the bottom is the hardware: CPU, memory, disks and network cards.

The big ideas

What you need to know

Everything is a file

Disks live at /dev/sda, process info lives under /proc. Tools that read files can inspect almost anything.

Distros are flavours

Ubuntu, Debian, Fedora and Rocky Linux share the same kernel but differ in package managers and defaults.

Small tools, piped together

Each command does one job well. You chain them with | to build bigger answers, like ps aux | grep nginx.

root is the superuser

root can do anything, including breaking the system. Work as a normal user and use sudo only when needed.

See it in code

Walk through the code

bash

1cat /etc/os-release   # which distro and version2uname -r              # kernel version3whoami                # your username4free -h               # memory in human units5df -h /               # disk space on the root disk6ls /proc | head       # running processes, shown as folders

1/3Find the distro name and the kernel version. Handy when a guide only works on one distro.

Run these on any new server you log in to. In thirty seconds you know what you are standing on.

Save yourself the pain

Common mistakes

Oops

Doing all your practice logged in as root because it never says 'permission denied'.

Do this instead

Use a normal user and sudo. Permission errors teach you how Linux security works, and protect you from typos.

Oops

Thinking Linux is one product, so every guide works the same everywhere.

Do this instead

Check your distro first. A command for Ubuntu (apt) may not exist on Rocky Linux (dnf).

Your mission

Get your own Linux box

~30 min

Quick check

Your friend runs a script with sudo and it deletes system files. Why was this possible?

Go deeper

1Set up a Linux environment (a VM, WSL, or a cloud free-tier instance) to practice hands-on.
2Learn the difference between major distributions (Ubuntu, CentOS/RHEL, Debian) at a high level.
3Practice basic commands daily until navigating a terminal feels natural, not intimidating.