Linux System Administration

Linux system administration is the practice of operating a host as a system, not a collection of commands. Your job is to keep intended services available while preserving security, evidence, and a route back from each change.

A Linux host has layers. The kernel manages processes, memory, devices, filesystems, and network interfaces. User space supplies shells, utilities, libraries, package tooling, and services. A distribution selects and integrates those parts. Administration crosses the boundaries between them.

The operating model

Start with observed behavior. Identify the component that owns it. Inspect its current state and recent evidence. Make the smallest reversible change that addresses the cause. Then verify the outcome.