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.

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.

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.

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.

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.

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.

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