Programmer’s Reference
Read service state, inspect logs, and understand units and timers.
Linux hosts using systemd. demo-worker.service is an illustrative unit, not a WGS production service.
Select a term for its definition, syntax, example, and common mistakes.
Read a service summary and get a concise active-state result.
systemctl status demo-worker.service --no-pager
systemctl is-active demo-worker.servicePractical useInspect a demo worker before attempting a repair.
Common mistakesstatus can return a nonzero code for inactive units. active does not prove the application is healthy.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)
List loaded services and installed service unit files.
systemctl list-units --type=service --all
systemctl list-unit-files --type=servicePractical useDistinguish current state from boot configuration in a demo view.
Common mistakesLoaded unit state and enablement at boot are different. A disabled service can still be running.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)
Show recent messages for a unit; follow new messages until Ctrl+C.
journalctl -u demo-worker.service -n 50 --no-pager
journalctl -u demo-worker.service -fPractical useInvestigate a staging backend failure.
Common mistakesYou may need sudo or journal group membership. Do not publish logs containing credentials or private data. Ctrl+C exits the viewer.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)
Read unit files/drop-ins and selected resolved properties.
systemctl cat demo-worker.service
systemctl show demo-worker.service -p FragmentPath -p User -p ExecStartPractical useCheck which demo executable is configured.
Common mistakesOutput can reveal private command arguments. Use fixed property selections and sanitize public examples.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)
Define a long-running demo Python worker under a pre-created unprivileged user.
[Unit]
Description=Demo worker
After=network.target
[Service]
Type=simple
User=demo-worker
WorkingDirectory=/srv/demo-worker
ExecStart=/usr/bin/python3 /srv/demo-worker/worker.py
Restart=on-failure
[Install]
WantedBy=multi-user.targetPractical usePrototype a separate staging worker; reuse the real application’s established unit for actual operations.
Common mistakesThe user, script, and directory must already exist. network.target does not guarantee external network readiness. Avoid embedding secrets in ExecStart.
Source: www.freedesktop.org documentation (1) · www.freedesktop.org documentation (2) · github.com documentation (3) · github.com documentation (4)
Check a demo unit file and tell the manager to reread unit definitions.
⚠ Caution: Changes the service manager’s loaded definitions.
systemd-analyze verify ./demo-worker.service
sudo systemctl daemon-reloadPractical useValidate a proposed staging unit before activating it.
Common mistakesdaemon-reload does not restart the application or reload its own configuration. Install the intended unit first; heed verification errors.
Source: www.freedesktop.org documentation (1) · www.freedesktop.org documentation (2) · github.com documentation (3) · github.com documentation (4)
Start a demo unit now and enable it for boot. Review stop/restart as separate actions.
⚠ Caution: Starts a process and changes boot behavior. stop/restart interrupt the service.
sudo systemctl start demo-worker.service
sudo systemctl enable demo-worker.service
# Separate actions, run only when intended:
# sudo systemctl stop demo-worker.service
# sudo systemctl restart demo-worker.servicePractical usePractice service lifecycle controls on an isolated demo worker.
Common mistakesenable alone does not start a service. restart may start an inactive service; stop interrupts current work.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)
List scheduled timers and inspect a demo timer’s definition.
systemctl list-timers --all
systemctl cat demo-backup.timerPractical useCheck a demo backup schedule alongside its result logs.
Common mistakesTimers trigger units; examine both the timer and its target service. Scheduling does not prove backups succeed.
Source: www.freedesktop.org documentation (1) · github.com documentation (2)