Systemd is a suite of fundamental building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and initializes the rest of the system. It is replacement to SysV in most modern Linux distributions.
Key Features
- Parallel startup of services.
- On-demand activation of daemons.
- Dependency-based service control.
Basic System Control
Get system status
Reboot the system
Power off the system
Suspend the system
Hibernate the system
Mixed sleep (hybrid sleep)
List all units
List all active units
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| systemctl list-units --state=active
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List all failed units
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| systemctl list-units --state=failed
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Service Management
Start a service
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| systemctl start <serviceName>.service
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Stop a service
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| systemctl stop <serviceName>.service
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Restart a service
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| systemctl restart <serviceName>.service
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Reload a service’s configuration (without full restart)
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| systemctl reload <serviceName>.service
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Get the status of a service
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| systemctl status <serviceName>.service
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Check if a service is enabled to start on boot
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| systemctl is-enabled <serviceName>.service
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Enable a service to start on boot
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| systemctl enable <serviceName>.service
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Disable a service from starting on boot
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| systemctl disable <serviceName>.service
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Mask a service (prevent it from being started)
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| systemctl mask <serviceName>.service
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Unmask a service (allow it to be started)
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| systemctl unmask <serviceName>.service
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Service Dependencies
Show a unit’s dependencies
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| systemctl list-dependencies <serviceName>.service
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Unit Files
Show the location of a unit file
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| systemctl show <serviceName>.service -p FragmentPath
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Edit a unit file
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| systemctl edit <serviceName>.service
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Example:
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| # Set the EDITOR at runtime
# `--full`: Edit the main unit file instead of creating a snippet.
EDITOR=vim systemctl edit apache2.service --full
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Show the contents of a unit file
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| systemctl cat <serviceName>.service
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Reload systemd’s unit files
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| systemctl daemon-reload
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Journal Control (Logging)
Journalctl is a command-line utility that allows you to view and query logs stored in the systemd journal. The journal is a structured, binary log format that collects logs from various sources, including the kernel, system services, and applications.
Show all logs
Show logs for a specific service
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| journalctl -u <serviceName>.service
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Show logs from boot
Follow logs in real-time
Show recent logs (e.g., last 10 minutes)
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| journalctl --since "10 min ago"
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Show logs since a specific time
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| journalctl --since "2025-03-15"
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Show logs until a specific time
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| journalctl --until "2025-03-15 12:00:00"
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Show logs within a time range
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| journalctl --since "yesterday" --until "now"
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Show kernel logs
Show logs and with explanations
Disk Usage
Show journal disk usage
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| journalctl --disk-usage
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Time Synchronization
Check the status of the time synchronization service
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| systemctl status systemd-timesyncd.service
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Other Useful Commands
Show system uptime
Show current system limits
Conclusion
I find this systemd cheat sheet incredibly useful for managing systems and services in Linux. It serves as a quick reference for the common tasks I handle daily. While systemd offers a wide range of features and options, this cheat sheet helps me easily recall essential commands, which significantly enhances my workflow. For more detailed information, I often refer to the official systemd documentation or use the man systemd command.