Systemctl Command Deep Dive and Usage Tutorial

In this tutorial, we explore how to use systemctl—the primary command-line tool for interacting with systemd—to manage services, sockets, mount points, and system states on modern Linux systems.

💻 Introduction to systemctl

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systemctl is the central tool used to control the systemd system and service manager.

systemd is a modern initialization system replacing the traditional SysV init process. It provides a unified framework for:

• Service management
• Process supervision
• Logging
• Boot analysis
• Dependency control

Most mainstream Linux distributions—including Ubuntu, Fedora, Debian, Rocky Linux, and Arch Linux—use systemd by default.

🚀 Getting Started with systemd and systemctl

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1. Check systemd version

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systemd --version

2. Locate systemd and systemctl binaries

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whereis systemd
whereis systemctl

3. Verify if systemd is running

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ps -eaf | grep [s]ystemd

4. Analyze system boot duration

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systemd-analyze

5. Analyze service startup times

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systemd-analyze blame

6. Visualize the boot chain

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systemd-analyze critical-chain

📦 Managing Units with systemctl

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7. List all available units

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systemctl list-unit-files

8. List all active units

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systemctl list-units

9. List all failed units

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systemctl --failed

10. Check if a service is enabled at boot

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systemctl is-enabled crond.service

11. Check service status

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systemctl status firewalld.service

12. List all services

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systemctl list-unit-files --type=service

🔧 Start, Stop, Restart, and Reload Services

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13. Manage a service (example: httpd)

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systemctl start httpd.service
systemctl restart httpd.service
systemctl stop httpd.service
systemctl reload httpd.service
systemctl status httpd.service

14. Enable/disable service at boot

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systemctl enable httpd.service
systemctl disable httpd.service

15. Mask/unmask a service

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systemctl mask httpd.service
systemctl unmask httpd.service

16. Kill a service process

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systemctl kill httpd

💾 Managing Mount Points

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17. List mount units

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systemctl list-unit-files --type=mount

18. Control mount units

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systemctl start tmp.mount
systemctl stop tmp.mount
systemctl restart tmp.mount
systemctl reload tmp.mount
systemctl status tmp.mount

19–20. Enable/disable/mask/unmask mount units

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systemctl enable tmp.mount
systemctl disable tmp.mount
systemctl mask tmp.mount
systemctl unmask tmp.mount

🔌 Managing Socket Units

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21. List socket units

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systemctl list-unit-files --type=socket

22. Control a socket (example: cups.socket)

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systemctl start cups.socket
systemctl restart cups.socket
systemctl stop cups.socket
systemctl reload cups.socket
systemctl status cups.socket

23–24. Enable/disable/mask/unmask sockets

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systemctl enable cups.socket
systemctl disable cups.socket
systemctl mask cups.socket
systemctl unmask cups.socket

📈 CPU Resource Management

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25. View CPU shares for a service

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systemctl show -p CPUShares httpd.service

26. Set CPU shares for a service

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systemctl set-property httpd.service CPUShares=2000

27. Display all service parameters

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systemctl show httpd

28. Display critical chain for a service

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systemd-analyze critical-chain httpd.service

29. List service dependencies

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systemctl list-dependencies httpd.service

🧩 Control Groups (cgroups)

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30. Display cgroup hierarchy

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systemd-cgls

31. View CPU, memory, and I/O activity

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systemd-cgtop

⚙️ Managing System Runlevels (Targets)

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32. Enter rescue mode

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systemctl rescue

33. Enter emergency mode

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systemctl emergency

34. Show default target

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systemctl get-default

35–36. Switch between graphical and multi-user modes

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systemctl isolate graphical.target
systemctl isolate multi-user.target

37. Change default runlevel

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systemctl set-default graphical.target
systemctl set-default multi-user.target

38. System power operations

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systemctl reboot
systemctl halt
systemctl suspend
systemctl hibernate
systemctl hybrid-sleep

📝 Summary

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This guide provides a complete, hands-on understanding of systemctl and systemd—covering:

• Unit management
• Boot analysis
• Service troubleshooting
• Resource control
• Runlevel/target operations
• Mount and socket management

Mastering systemctl is essential for anyone working in Linux system administration, DevOps, or SRE roles.