The three families you'll actually meet
Windows 10 / 11
The one sitting on almost every desk
Built for one person using one machine at a time — a laptop, a desktop. This is what most employees log into every morning. Administering it means managing updates, user accounts, installed software, and local security settings on an individual device.
Windows Server
Not for sitting in front of — for serving many
Same underlying Windows lineage, built instead to run unattended in a server room or datacenter, serving files, hosting a database, or running Active Directory for hundreds of users at once. Currently on Windows Server 2025. Nobody "uses" a server the way they use a laptop — they connect to what it's serving.
Linux (Ubuntu, RHEL)
The one running most of the internet, quietly
Open-source, free to use, and the default choice for web servers, cloud infrastructure, and anything where cost and flexibility matter more than a familiar desktop. Ubuntu favours ease of use; RHEL (Red Hat Enterprise Linux) favours enterprise support contracts. Different audiences, same underlying philosophy.
Storage & Backup Basics
The one habit that turns a disaster into an inconvenience
Every OS above manages disks the same way underneath: a drive gets formatted, partitioned, and mounted before anything can be stored on it. RAID spreads or duplicates data across multiple physical disks so one drive failing doesn't mean data loss — but RAID is not a backup; it protects against hardware failure, not against someone deleting the wrong file. The industry's simplest durable rule is 3-2-1: 3 copies, on 2 different types of media, with 1 copy stored somewhere else entirely. Every strategy in Resilience & Continuity is this same idea, automated and scaled up.
Why a company runs all three at once
REAL-WORLD SCENARIO
A 50-person company doesn't pick "the best" operating system — it picks the right one for each job:
Every employee's laptop runs Windows 11, because it's familiar, and the apps staff need (Office, line-of-business software) are built for it.
The internal file server — the one holding shared drives and running Active Directory — runs Windows Server, because it integrates directly with those same Windows laptops.
The public website and the API behind the company's app run on Ubuntu servers, because Linux is cheaper to run at scale and is what most web hosting and cloud infrastructure assumes by default.
Nobody in this company thinks of this as "three separate operating systems fighting for dominance." They're just three tools, each doing the job it's actually good at.
What "administering" one actually means
Regardless of which of the three you're on, the job is conceptually the same — only the exact menus and commands change:
01
Managing users and permissions
Deciding who can log in, and once they're in, what they're allowed to touch.
02
Installing and updating software
Keeping the OS itself and everything running on it patched — the single biggest lever against getting breached.
03
Monitoring what's running
Checking which processes are using CPU, memory, and disk — and noticing when something's using far more than it should.
04
Reading the logs when something breaks
Every OS keeps a record of what happened before a crash or an error — Event Viewer on Windows, log files on Linux. The habit of checking them first is what separates a fast fix from hours of guessing.
A note on this cluster's scope
This page deliberately stays at the concept level rather than giving you exact click-paths through a specific Windows or Linux version — those menus shift between releases, and a screenshot-perfect walkthrough goes stale fast. What's above is durable regardless of which exact version you're on.
Where this leads
Once a machine is running, the next questions are usually "how does it prove who's allowed to log in" — covered in On-Premises Identity & Directory Services — and "what if I need many of these machines, not just one" — covered in Virtualisation. At cloud scale, this entire idea becomes Virtual Machines & Compute, and the storage/backup basics above become Storage & Data and Resilience & Continuity — both of which assume you already know the difference between RAID and a real backup.
Certification this maps to
CompTIA A+ (Core 1 & Core 2)