MODULE 3: Services, Processes & System Operations

How do administrators keep Linux servers running, healthy, and responsive in enterprise environments?

What You Will Learn in This Module

By the end of Module 3, learners will be able to:

• Understand Linux services and daemons
• Start, stop, enable, and restart services
• Monitor running processes
• Install and update software packages
• Read system logs
• Monitor CPU, memory, and disk usage
• Apply professional operational workflows

Lesson 1: What Are Services & Daemons?

Linux servers run background programs called:

services (daemons)

Examples:

• SSH server
• Web server (Apache/Nginx)
• Database (MySQL/PostgreSQL)
• Cron scheduler

These run continuously to provide functionality.

Enterprise Meaning

If services stop:

• websites go down
• users lose access
• business stops

Admins must control services.

Lesson 2:  Managing Services with systemctl

Modern Linux uses systemd.

Admins manage services using:

• systemctl start
• systemctl stop
• systemctl restart
• systemctl status
• systemctl enable

Example:

Restart SSH service:

systemctl restart ssh

Check status:

systemctl status ssh

Enterprise Tip

Always check status after changes.

Lesson 3: Understanding Processes

A process is a running program.

Admins view processes with:

• ps
• top
• htop

These show:

• CPU usage
• memory usage
• running tasks

Why This Matters

High CPU or memory often means:

• runaway application
• misconfiguration
• attack

Admins must investigate.

Lesson 4: Stopping Problem Processes

Sometimes apps freeze.

Admins use:

• kill
• kill -9

To stop broken processes.

But always investigate cause first.

Lesson 5: Installing & Updating Software (Package Management)

Linux installs software via package managers:

Ubuntu/Debian:

• apt

CentOS/Rocky:

• yum / dnf

Admins use these to:

• install applications
• update security patches
• remove unused software

Enterprise Rule

Always patch servers regularly.

Unpatched servers = hacked servers.

Lesson 6: System Logs (Where the Truth Lives)

Linux stores logs in:

/var/log

Admins use:

• journalctl
• tail
• less

To read logs.

Logs show:

• service failures
• login attempts
• errors
• system events

Example:

SSH failed login appears in auth logs.

Lesson 7: Monitoring System Resources

Admins monitor:

• CPU (top)
• memory (free)
• disk (df -h)
• load average

Why?

To prevent:

• crashes
• slow systems
• full disks

Lesson 8: Startup Services

Some services must start automatically.

Admins use:

systemctl enable servicename

So, services survive reboots.

Lesson 9: Enterprise Operational Workflow

Real admins follow this cycle:

1. Monitor system
2. Detect issue
3. Check logs
4. Fix service
5. Validate
6. Document

Never random guessing.

Always evidence-driven.

Lesson 10: Practical Self Practice

Learners practice:

• installing a service
• starting/stopping it
• viewing logs
• checking CPU/memory
• simulating service failure
• restoring service

Scenario:
Web service stopped → find cause → restart → confirm.

MODULE 3 SUMMARY

By completing Module 3, learners now understand:

• services & daemons
• systemctl operations
• processes monitoring
• package management
• reading logs
• resource monitoring
• enterprise troubleshooting workflow

This module answers:

“How do I operate and maintain Linux servers professionally?”