Linux Systemd Cheat Sheet

Systemd is the init system used in modern Linux distributions for managing services, processes, logs, and boot configurations. Below is a cheat sheet with essential systemd commands.

Table of Contents

Managing Services

Command	Description
systemctl start <service>	Start a service.
systemctl stop <service>	Stop a service.
systemctl restart <service>	Restart a service.
systemctl reload <service>	Reload configuration without restarting.
systemctl status <service>	Check service status.
systemctl enable <service>	Enable service to start at boot.
systemctl disable <service>	Disable service from starting at boot.
systemctl is-enabled <service>	Check if a service is enabled.
systemctl mask <service>	Prevent a service from starting.
systemctl unmask <service>	Unmask (re-enable) a masked service.

Example: Restart and Enable Apache

sudo systemctl restart apache2
sudo systemctl enable apache2

Checking System Boot and Performance

Command	Description
systemctl list-units –type=service	List all running services.
systemctl list-units –failed	Show failed services.
systemctl list-timers	Show scheduled system timers (cron alternative).
systemd-analyze	Show boot time analysis.
systemd-analyze blame	List services causing slow boot.

Example: Check Slow Boot Services

systemd-analyze blame

Managing System Startup (Targets)

Systemd uses “targets” instead of traditional runlevels.

Command	Description
systemctl get-default	Show current default target.
systemctl set-default multi-user.target	Set system to boot into multi-user mode (no GUI).
systemctl set-default graphical.target	Set system to boot into GUI mode.
systemctl isolate rescue.target	Switch to rescue mode (single-user mode).

Example: Boot into Text Mode

sudo systemctl set-default multi-user.target

Managing Systemd Unit Files

Systemd services are defined in unit files stored in:

/etc/systemd/system/ (custom services)
/lib/systemd/system/ (system-installed services)

Command	Description
systemctl cat <service>	Show service unit file.
systemctl edit –full <service>	Edit service unit file.
systemctl daemon-reload	Reload systemd after editing unit files.

Example: Edit and Reload a Service

sudo systemctl edit --full myservice
sudo systemctl daemon-reload
sudo systemctl restart myservice

Viewing System Logs (Journalctl)

Systemd uses journald to store logs.

Command	Description
journalctl -xe	Show recent logs with errors.
journalctl -u <service>	View logs for a specific service.
journalctl –since “1 hour ago”	View logs from the last hour.
journalctl -b	Show logs from the last boot.
journalctl –disk-usage	Check journal log size.

Example: View Apache Logs

journalctl -u apache2 --since "yesterday"

Example: Create a Custom Systemd Service

Create a new service file

sudo nano /etc/systemd/system/myapp.service

Add the following configuration

[Unit]
Description=My Custom Application
After=network.target

[Service]
ExecStart=/usr/bin/python3 /home/user/myapp.py
Restart=always
User=user
Group=user

[Install]
WantedBy=multi-user.target

Enable and Start the Service

sudo systemctl daemon-reload
sudo systemctl enable myapp.service
sudo systemctl start myapp.service
sudo systemctl status myapp.service

Other Useful Commands

Command	Description
hostnamectl	Show system hostname and OS details.
timedatectl	Show and set system time & timezones.
localectl	Display system locale settings.
loginctl	Manage user sessions.

Summary

systemctl manages services and targets.
journalctl handles logs.
Systemd replaces cron for scheduled tasks (using timers).
Custom unit files allow custom services.

Systemd is a powerful tool—this cheat sheet helps simplify managing your Linux system!

Download PDF of cheatsheet