Managing Services in Linux – systemd & init (Complete Guide)

Managing Services in Linux – systemd & init

📌 Introduction

Managing Services in Linux: Managing services is a crucial aspect of Linux system administration. Whether you’re starting, stopping, or monitoring system services, understanding the underlying service management system is essential.

Linux primarily uses systemd and init for managing services, with systemd being the modern replacement for init in most distributions. This blog provides a comprehensive guide on managing services using systemd and init, covering commands, configurations, and best practices.

📖 In this guide, you’ll learn:
✔️ The role of systemd and init in Linux
✔️ How to start, stop, restart, and manage services
✔️ Differences between systemd and init
✔️ Troubleshooting common service management issues
✔️ Best practices for handling Linux services

Let’s dive deep into Linux service management! 🛠️

🔍 Understanding Service Management in Linux

🧐 What is a Service in Linux?

A service in Linux is a background process that runs continuously to provide functionalities like networking, logging, database management, or web hosting. These services are typically managed by an init system, which ensures they start at boot and function as expected.

Linux has used different service management systems over time:

✅ SysVinit – The traditional initialization system.
✅ Upstart – A short-lived replacement for SysVinit.
✅ systemd – The modern, widely used service manager.

Let’s explore each in detail.

🛠️ Understanding systemd – The Modern Service Manager

systemd is the default system and service manager in most modern Linux distributions, including:

Ubuntu (since 15.04)
CentOS/RHEL (since version 7)
Debian (since 8 “Jessie”)
Fedora
Arch Linux

⚡ Why systemd?

✅ Faster boot time due to parallel service startup.
✅ Centralized logging via journalctl.
✅ Dependency tracking to handle service dependencies.
✅ Socket-based activation for efficient resource usage.
✅ Unified configuration with .service unit files.

📝 Managing Services with systemd

1️⃣ Checking Service Status

Use systemctl status to check if a service is running:

systemctl status apache2

🔹 Output Example:

● apache2.service - The Apache HTTP Server
   Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2025-03-20 12:45:00 UTC; 5h 10min ago

2️⃣ Starting a Service

To start a service manually, use:

systemctl start apache2

3️⃣ Stopping a Service

To stop a running service:

systemctl stop apache2

4️⃣ Restarting a Service

If you need to restart a service:

systemctl restart apache2

5️⃣ Enabling a Service at Boot

To start a service automatically at system startup:

systemctl enable apache2

6️⃣ Disabling a Service at Boot

To prevent a service from starting at boot:

systemctl disable apache2

7️⃣ Reloading a Service Configuration

If you make changes to a service configuration file, reload it:

systemctl reload apache2

8️⃣ Viewing All Active Services

To list all running services:

systemctl list-units --type=service

🖥️ Understanding Init – The Traditional Service Manager

Before systemd, SysVinit was the standard service manager in Linux. It uses shell scripts located in /etc/init.d/ to start and stop services.

📂 Init Service Management Commands

1️⃣ Starting a Service

service apache2 start

2️⃣ Stopping a Service

service apache2 stop

3️⃣ Restarting a Service

service apache2 restart

4️⃣ Checking Service Status

service apache2 status

5️⃣ Enabling a Service at Boot

update-rc.d apache2 defaults

6️⃣ Disabling a Service at Boot

update-rc.d apache2 remove

📊 systemd vs. init – Key Differences

Feature	systemd	Init (SysVinit)
Boot Speed	Faster due to parallel startup	Slower due to sequential startup
Service Tracking	Uses unit files	Uses scripts in `/etc/init.d/`
Logging	Centralized with `journalctl`	Logs scattered across `/var/log/`
Process Monitoring	Tracks processes with `cgroups`	No built-in process tracking
Dependency Management	Yes	Limited

✅ Verdict: systemd is faster, more reliable, and feature-rich compared to init.

🚀 Advanced systemd Features

📌 1. Checking Boot Performance

systemd-analyze blame

Shows which services slow down boot time.

📌 2. Checking Logs with journalctl

journalctl -u apache2 --since today

Shows logs for apache2 service from today.

📌 3. Killing Unresponsive Services

bashCopyEditsystemctl kill apache2

🛠️ Troubleshooting Common Service Issues

🧐 Service Not Starting?

1️⃣ Check logs:

journalctl -xe

2️⃣ Check dependencies:

systemctl list-dependencies apache2

3️⃣ Restart systemd:

systemctl daemon-reexec

📌 Conclusion

✅ systemd is the modern, efficient service manager used by most Linux distributions.
✅ Init (SysVinit) is still found in older systems but lacks many modern features.
✅ systemctl commands simplify service management, making it easier to start, stop, and monitor services.

Mastering systemd ensures efficient service management and helps troubleshoot Linux systems effectively. 🚀

📚 Learn More:

🔹 What’s Next? Learn about Linux process management and log analysis for deeper system insights!