Linux systemctl & journalctl (systemd) Cheat Sheet

Essential systemd command reference for Linux server administrators. Managing services, units, boot targets, timers, and streaming system logs.

Service Lifecycle Management

Start a stopped system service immediatelysudo systemctl start <service>

Stop a running system service immediatelysudo systemctl stop <service>

Stop and restart servicesudo systemctl restart <service>

Reload configuration without dropping active connectionssudo systemctl reload <service>

View service state, PID, memory, and recent log messagessudo systemctl status <service>

Enabling on Boot & Daemon Reload

Configure service to automatically launch on system bootsudo systemctl enable <service>

Prevent service from launching on system bootsudo systemctl disable <service>

Reload all systemd unit configuration files after editingsudo systemctl daemon-reload

Returns 0 if service is currently running (script friendly)systemctl is-active <service>

Check if service is configured to launch on bootsystemctl is-enabled <service>

Streaming Logs with journalctl

Follow live streaming log output for a specific servicejournalctl -u <service> -f

Show the last 100 log lines for a specific servicejournalctl -u <service> -n 100

Filter logs generated within the last hourjournalctl -u <service> --since "1 hour ago"

Show all error-level logs from current boot sessionjournalctl -p err -b

Clean up journal logs older than 3 days to free disk spacesudo journalctl --vacuum-time=3d

Frequently Asked Questions

• Why do I need to run systemctl daemon-reload?

systemd caches unit files in memory. If you edit, create, or delete a `.service` file under `/etc/systemd/system/`, you must execute `systemctl daemon-reload` so systemd re-reads the updated configuration.