Blog
4 min read

What Is Linux? A Beginner's Guide for People Building Apps

Linux runs most of the world's servers — including, probably, the one your app will live on. What Linux is, kernels vs distributions, Ubuntu vs Debian vs Alpine, how it differs from Windows and macOS, and the handful of Linux facts that prevent deploy bugs.

You may never install Linux on your own computer, but your app will almost certainly run on it. The overwhelming majority of web servers, cloud machines and containers run Linux. Knowing a little about it explains a lot of "works on my machine" problems.

The short version

Linux is a free, open-source operating system — the same kind of software as Windows or macOS: it manages the hardware, runs programs, handles files and networking. It was started in 1991 by Linus Torvalds and is now developed by thousands of people and companies.

It runs servers, Android phones, routers, smart TVs, supercomputers and plenty of laptops.

Kernel vs distribution

Strictly, "Linux" is the kernel — the core that talks to the hardware. To be useful, the kernel is packaged with tools, a package manager and settings into a distribution ("distro"). That's what you actually choose:

Distribution Where you'll see it
Ubuntu The most common choice for servers and cloud machines; beginner-friendly
Debian Stable and conservative; Ubuntu is based on it; common in Docker images
Alpine Tiny; popular for Docker images; uses a different C library, which occasionally causes surprises
Fedora / RHEL / Rocky / AlmaLinux Common in companies and enterprise servers

For a first server, Ubuntu LTS (long-term support) is the safe default.

Why servers run Linux

  • It's free — no licence per machine.
  • It's lightweight — no graphical desktop needed on a server.
  • It's controlled from the terminal, which is easy to automate and reach remotely over SSH. (The terminal for complete beginners.)
  • It's what the tools assume. Docker containers are Linux. Most deployment guides, AI agents and CI systems assume a Linux environment. (What is Docker?)

Linux vs Windows vs macOS for developers

macOS is a Unix-like system, a close cousin of Linux, so most commands feel the same. Windows is different — but WSL (Windows Subsystem for Linux) runs a real Linux environment inside Windows, and many developers use it.

Linux facts that prevent deploy bugs

These differences cause a surprising share of "it worked locally" bugs:

1. File names are case-sensitive

On Linux, Logo.png and logo.png are two different files. On Windows and (by default) macOS, they're the same. So import Header from "./components/header" works on your laptop and fails on the server if the file is called Header.tsx. (File paths explained.)

2. Paths use forward slashes

/home/app/uploads, never C:\Users\.... Code with hardcoded Windows paths breaks on Linux.

3. Line endings

Windows ends lines with \r\n; Linux uses \n. A shell script saved with Windows line endings fails on Linux with a confusing /bin/bash^M: bad interpreter error. Git can normalise these with a .gitattributes file.

4. Permissions

Every file has an owner and permissions for reading, writing and executing. "Permission denied" errors on a server usually trace back to this. See Linux file permissions and chmod explained.

5. Root and sudo

root is the all-powerful administrator account. Day-to-day work happens as a normal user, with sudo to run individual commands as root. Running your app as root is a security risk — if it's compromised, so is the whole machine.

A few commands to recognise

pwd            # where am I?
ls -la         # list files, including hidden ones, with permissions
cd /var/www    # change directory
cat file.txt   # print a file
df -h          # disk space
free -h        # memory
top            # what's running and using CPU

How to try Linux

  • Windows: install WSL (wsl --install in an administrator terminal).
  • Mac: the Terminal app already gives you a Unix-like environment.
  • Anywhere: a cloud server or a cloud development environment gives you a real Linux machine in the browser. (Cloud development environments vs local setup.)

The summary

  • Linux is a free, open-source operating system that runs most servers and containers.
  • You choose a distribution; Ubuntu LTS is the usual first pick.
  • Case-sensitive file names, forward slashes, line endings and permissions cause many deploy bugs.
  • WSL lets you use Linux on Windows.

EasySpawn servers run Linux — the same case-sensitive, permission-checked environment production uses — so the bugs above show up while you're building, not after you deploy. See how it works or join the waitlist.

Related: What Is a VPS? · What Is a Server? · SSH Keys Explained · Why Does My App Work Locally but Not in Production? · What Is WSL?

Keep reading