Linux

Core Idea

Linux is the operating-system kernel at the center of a family of systems built from that kernel, system tools, libraries, services, shells, and applications.

What You Are Using In This Course

You are using a shared Linux server. The exact distribution can be checked with:

cat /etc/os-release
uname -a

/etc/os-release identifies the distribution. uname reports kernel and machine information.

Kernel, Distribution, Userland

• Kernel: manages processes, memory, filesystems, devices, and networking.
• Distribution: packages the kernel with tools, defaults, package repositories, and release policy.
• Userland: the commands and services you run, such as Bash, OpenSSH, Caddy, systemd, git, and curl.

Why Linux Is Useful For Makers

• It exposes real systems as files, processes, sockets, logs, users, and permissions.
• It rewards small tools joined together.
• It runs servers, laptops, phones, routers, containers, and embedded systems.
• It is documented through manual pages and public source.

Common Confusions

• Linux is not the same thing as Bash. Bash is one shell that runs on Linux.
• Linux is not the same thing as Ubuntu or Debian. Those are distributions.
• The desktop is optional. Servers often have no graphical interface.
• A command can be a Linux command, a GNU command, a Bash builtin, or a package-provided program.

Proof Check

Run cat /etc/os-release and identify the distribution name. Run uname -r and identify the kernel release.

Docs Pointers

• Run man uname.
• Read the Debian Handbook.
• Read kernel.org: What is Linux?.
• Read Unix to understand the older design tradition Linux grew from.