3 PART III Intermediate System Administration

Table of Contents

Overview

Part III moves from using Linux to administering it. You’ll start thinking like the person responsible for keeping systems running, secure, and recoverable, not just as a user running commands.

This part assumes you are already comfortable with:

Navigating the filesystem
Using the shell and basic scripting
Managing packages
Understanding basic concepts like users, permissions, and processes

You’ll now apply those skills to real-world administration tasks.

Goals of Part III

By the end of this part, you should be able to:

Understand and control how services start, stop, and log via systemd
Manage disks, partitions, and filesystems, and handle backups/archives
Configure basic networking and troubleshoot common connectivity issues
Create and manage multiple users and groups on a shared system
Monitor the health and performance of a Linux system
Design and implement basic backup and restore strategies
Apply foundational security measures to harden a Linux host

You are not yet building complex production clusters or doing deep kernel tuning—that comes later—but you will cover everything needed to run a small server or workstation responsibly.

How This Part Is Structured

Part III is divided into practical topics, each focusing on a key admin area:

Systemd and Service Management
How Linux starts, stops, and supervises services on modern distributions:

Understanding systemd as the init system and service manager
Using systemctl to manage services and boot targets
Viewing and filtering logs with journalctl
Defining simple custom services for your own scripts or apps

Storage and Filesystems
Working with disks and on-disk data structures:

Mapping physical devices to partitions
Choosing and creating common filesystems (like EXT4, XFS, Btrfs)
Mounting and unmounting filesystems (both temporarily and persistently)
Checking disk space and usage patterns
Using classic archiving and compression tools for backups or transfers

Networking Fundamentals
Giving your system an identity on a network and keeping it reachable:

Understanding IP addresses, subnets, and basic routing concepts
How DNS and hostnames fit into name resolution
Using standard network diagnostic tools
Editing and applying network configuration on typical Linux systems

User and Group Administration
Scaling beyond a single personal account:

Where account information is stored
Creating, modifying, and removing user accounts
Setting password aging and complexity policies
Group-based access control and membership management
Basic shell customization for users

System Monitoring
Watching what the system is doing, in real time and historically:

Checking CPU, RAM, and swap usage
Monitoring disk utilization and I/O behavior
Understanding the role of /var/log and key system logs
Measuring and troubleshooting slow boots
Verifying that essential services are running correctly

Backup and Restore
Preparing for failure and human mistakes:

Designing simple backup strategies and schedules
Using rsync efficiently for local and remote backups
Creating and restoring tar archives
Understanding snapshot-based backup systems conceptually
Automating backup routines with existing tools and scripts

Basic System Security
Protecting a single host from common threats:

Enabling and managing host firewalls (UFW or firewalld)
Controlling authentication rules (passwords, lockouts, etc.)
Hardening SSH access for remote logins
Recognizing the role of MAC systems like SELinux and AppArmor
Getting started with intrusion detection tools and ideas

Each of these topics focuses on practical, admin-level tasks. You’ll see common commands, configuration file locations, and workflows that most system administrators use daily.

How to Approach This Part

To get the most from Part III:

Use a test machine or virtual machine
You will change system-wide settings. A VM lets you experiment freely.
Make small, reversible changes
Before editing configuration files, make backups like:
cp /etc/somefile.conf /etc/somefile.conf.bak
Practice end-to-end workflows
Don’t just learn individual commands. For example:

Install a service
Enable it with systemd
Expose it on the network
Monitor its logs
Back up its data

Connect the chapters
For example:

Use user and group management together with filesystem permissions.
Combine rsync and tar with cron (from shell scripting) to automate backups.
Relate firewall rules to the network services you configure.

As you progress, you’ll transition from “Can I do this on my machine?” to “Could I responsibly maintain this system for others?”, which is the core mindset of a Linux system administrator.

3.1 Systemd and Service Management

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