k1.1 — Distributions & Families: What “Linux” Is (and Isn’t) 🌍

What people mean when they say “Linux”
In everyday dev/admin talk, “Linux” usually refers to an entire operating system stack, not just one component:
Linux kernel
The core that handles:
processes and scheduling
memory management
networking
hardware drivers
Userland tools
The standard command-line tools you’ll use constantly, such as:
ls, 
cp, 
mv, 
rm, 
find
grep, 
sed, 
awk
tar, 
ssh, 
curl
Init / service manager
On most modern distros, this is systemd (so services behave similarly across many distributions).
Package manager + repositories
How software is installed and updated (this is one of the biggest practical differences across distros).
Defaults & policies
Security frameworks, filesystem defaults, preinstalled tools, and “the distro’s way” of doing common tasks.
What a “distribution” actually is
A Linux distribution (distro) is a curated bundle of the components above, plus:
a release philosophy (stable vs fast-moving)
a packaging system and official repositories
default configuration choices
documentation/community norms
So you’re not learning a completely different OS each time—you’re learning the same core concepts with different “packaging and defaults.”
The main families you’ll encounter (server/web world)
For web development and WordPress hosting, these families matter most:
Debian family
Debian (very stability-focused, conservative updates)
Ubuntu (based on Debian; very common, especially Ubuntu LTS on servers)
Typical traits:
uses APT (
apt)
huge ecosystem of tutorials and packages
RHEL family (Red Hat Enterprise Linux–compatible)
Rocky Linux, AlmaLinux (common for enterprise-style servers and some tooling stacks)
Typical traits:
uses DNF (
dnf, historically 
yum)
SELinux is commonly enabled and relevant
What’s shared across most distros (the “learn once” core)
If you learn these well, you can function on almost any mainstream Linux server:
filesystem concepts and common directories (you’ll cover this in k3)
permissions and ownership (
chmod, 
chown)
processes and signals (
ps, 
kill)
service management concepts (often via 
systemctl)
networking basics (ports, DNS, 
curl, 
ss)
SSH and key-based access
What this means for your course goal
Your plan—learn cross-distro fundamentals first without committing—works because:
the core Linux skills transfer extremely well
later, you mainly “translate”:
apt ↔ 
dnf
AppArmor ↔ SELinux
UFW ↔ firewalld
slightly different defaults/paths
Tiny self-check ✅
Answer these without Googling (it’s fine if you can’t yet):
What’s the kernel responsible for (in one sentence)?
Name two things that are usually different between Debian-based and RHEL-based distros.
What’s one Linux skill that should transfer across almost all distros?
If you want, reply with your answers and I’ll correct/clarify briefly.