Infrastructure & Operations › Linux & Servers

Linux

The operating system most servers run.

Also known as: GNU/Linux, Linux OS, Linux kernel

Linux is an operating system kernel, plus the tools around it (a shell, system utilities, a package manager), bundled into a distribution such as Ubuntu, Debian, Fedora or Alpine. Most servers, cloud machines and containers run on it, so as a backend or data engineer you will meet it constantly even if your laptop runs something else.

Why learn it

Deploying, debugging and operating software means working on Linux machines, usually through a terminal over SSH, with no graphical interface. The skills transfer between distributions because the basics are shared.

The core ideas

• Everything is a file (almost). Devices, processes and settings are exposed through the file system, so the same tools work on all of them. See the directory structure.
• The shell is the main interface. You combine small commands with pipes: grep ERROR app.log | sort | uniq -c. See shell.
• Permissions control everything. Every file has an owner and read/write/execute bits. See file permissions and sudo and root.
• Software comes from a package manager rather than downloaded installers. See OS package managers.
• Services are run by an init system, most often systemd.

Starter commands

pwd                # where am I
ls -la             # list files, including hidden, with permissions
cd /var/log        # change directory
cat app.log        # print a file
less app.log       # page through a file (q to quit)
man ls             # read the manual for a command

The classic early mistake is running destructive commands (especially rm -rf and anything with sudo) without reading the path twice. Distributions differ in details such as package manager and file locations, so check the docs for the one you use.