What is Linux?

The operating system behind most servers and the cloud-why it matters.

Why Linux everywhere?

Linux is an open-source operating system kernel. It runs on most servers, embedded devices, and is the base for many cloud workloads. Learning the basics-filesystem, processes, shells, and permissions-helps you work with almost any server or container.

Linux dominates servers and cloud because it's reliable, performant, and free. Most cloud providers use Linux for VMs and containers. Even with managed services, knowing Linux helps you troubleshoot and optimize.

Where Linux runs

ServersMost web & app servers run Linux

Cloud VMsAWS, Azure, GCP default to Linux

ContainersDocker & Kubernetes are built on Linux

EmbeddedRouters, IoT, phones, cars

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Why it matters

Linux is free, open-source, and runs most servers and cloud VMs. Learning filesystem, processes, shells, and permissions helps you work with almost any server or container.

The Linux filesystem

Linux uses a hierarchical filesystem starting at root (/). Key directories: /home (user files), /etc (config), /var (variable data), /tmp (temp), /usr (programs), /bin (essential binaries).

Everything in Linux is a file-devices, processes, and network connections appear as files. This unified interface makes the system consistent and scriptable.

File permissions control read/write/execute for owner, group, and others. Use chmod to change permissions and chown to change ownership. Same ideas apply to cloud storage and object permissions.

Key Linux Directories

/homeUser files

/etcConfiguration

/varVariable data

/tmpTemporary files

/usrUser programs

/binEssential binaries

File Permissions Example

-rwxr-xr--Owner: read/write/execute | Group: read/execute | Others: read

drwxrwxrwxDirectory with full permissions for all

Use chmod 755 file to set permissions numerically.

Processes and system management

Processes are running programs. Each has a PID (process ID) and runs with specific permissions. ps lists processes, top shows them live, kill terminates them.

systemd (or init) is the process manager that starts all other processes. It manages services, dependencies, and logging. You'll use it to start, stop, and restart services on servers.

Daemons are background processes (web servers, databases, cron). Understanding how to manage them is essential for production.

Process commands

ps auxList all processes

topLive process monitor

kill -9 <PID>Terminate a process

systemd

Starts and manages all services (init)

Daemons

Background services (web, DB, cron)

The command line and shells

The command line (shell) is the main interface for Linux. Bash is most common; zsh and fish are popular alternatives. The shell runs commands, scripts, and automation.

Essential commands: ls (list), cd (change directory), grep (search), find (find files), cat (read file). Use | to pipe output between commands; > and >> redirect output to files.

Shell scripts automate repetitive tasks-essential for DevOps and system administration.

Essential Linux Commands

File Operations

ls -lacd /pathcat file.txt

Process Management

ps auxtopkill -9 PID

Package management

Package managers install, update, and remove software. Each distro has one: apt (Debian/Ubuntu), yum/dnf (RHEL/Fedora), pacman (Arch).

They resolve dependencies automatically and deliver security patches. Keeping systems patched is critical.

In cloud and containers you'll use them to install dependencies and build base images.

Package managers by distro

apt

Debian / Ubuntu

apt install <pkg>

dnf / yum

Fedora / RHEL / CentOS

dnf install <pkg>

pacman

Arch Linux

pacman -S <pkg>

Package managers resolve dependencies and apply security updates—critical for keeping servers and containers patched.

Concepts that transfer

Processes, memory, file permissions, and the CLI apply everywhere-AWS, Azure, GCP, or your own data center. You'll often be working with Linux underneath.

Docker and Kubernetes are built on Linux. Knowing Linux helps you debug containers and tune performance.

Even with managed services, Linux knowledge helps you troubleshoot, optimize, and make better infrastructure decisions.

Linux skills apply everywhere

Containers

Docker & Kubernetes are built on Linux. Knowing processes, namespaces, and the filesystem helps you debug and tune containers.

Cloud

AWS, Azure, GCP VMs and serverless run on Linux. Understanding the CLI and permissions helps you operate and secure workloads.

Troubleshooting

When something breaks, you'll SSH into a Linux box. Logs, top, disk usage, and permissions are your daily tools.

Interactive: Filesystem, processes & permissions

Explore the hierarchy, process tree, and how permissions and users/groups work—without walls of text.

Ready to see how this works in the cloud?

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