Systemd Praxis Lösungen

Erstellen von Units

• cat /etc/systemd/system/date1.service

[Unit]
Description=Simple Unit

[Service]
Type=simple
ExecStart=/usr/local/sbin/test-system.sh 1

[Install]
WantedBy=default.target

• cat /etc/systemd/system/date2.service

[Unit]
Description=Simple Unit

[Service]
Type=simple
ExecStart=/usr/local/sbin/test-system.sh 2

[Install]
WantedBy=default.target

• cat /etc/systemd/system/date3.service

[Unit]
Description=Simple Unit

[Service]
Type=simple
ExecStart=/usr/local/sbin/test-system.sh 3

[Install]
WantedBy=default.target

• systemctl start date1
• systemctl start date2
• systemctl start date3
• tail /tmp/test-system.log

Analyse der gestarteten Units

• RemainAfterExit=yes hinterlässt den Service im activen Zustand
• systemctl status date3

● date3.service - Simple Unit
Loaded: loaded (/etc/systemd/system/date3.service; disabled; vendor preset: enabled)
Active: active (exited) since Tue 2023-01-10 11:17:02 CET; 40min ago
Main PID: 11089 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 1129)
Memory: 0B
CPU: 0
CGroup: /system.slice/date3.service
    
Jan 10 11:17:02 debian-test systemd[1]: Starting Simple Unit...
Jan 10 11:17:02 debian-test systemd[1]: Finished Simple Unit.

• systemctl status date1

● date1.service - Simple Unit
Loaded: loaded (/etc/systemd/system/date1.service; disabled; vendor preset: enabled)
Active: inactive (dead) since Tue 2023-01-10 12:02:16 CET; 46s ago
Process: 13868 ExecStart=/usr/local/sbin/test-system.sh 1 (code=exited, status=0/SUCCESS)
Main PID: 13868 (code=exited, status=0/SUCCESS)
CPU: 7ms

Jan 10 12:02:16 debian-test systemd[1]: Starting Simple Unit...
Jan 10 12:02:16 debian-test systemd[1]: date1.service: Succeeded.
Jan 10 12:02:16 debian-test systemd[1]: Finished Simple Unit.

Unit Abhängigkeiten definieren

• systemctl enable date1
• systemctl enable date2
• systemctl enable date3
• reboot
• Die Skripte werden in einer zufälligen Reihenfolge gestartet
• cat /etc/systemd/system/date1.service

[Unit]
Description=Simple Unit
Wants=date2.service
After=date2.service

[Service]
Type=oneshot
ExecStart=/usr/local/sbin/test-system.sh 1

[Install]
WantedBy=default.target

• cat /etc/systemd/system/date2.service

[Unit]
Description=Simple Unit
Wants=date3.service
After=date3.service

[Service]
Type=oneshot
ExecStart=/usr/local/sbin/test-system.sh 2

[Install]
WantedBy=default.target

• cat /etc/systemd/system/date3.service

[Unit]
Description=Simple Unit

[Service]
Type=oneshot
ExecStart=/usr/local/sbin/test-system.sh 3

[Install]
WantedBy=default.target

• tail -n 3 /tmp/test-system.log

test-system-3 Tue 10 Jan 2023 12:17:37 PM CET
test-system-2 Tue 10 Jan 2023 12:17:37 PM CET
test-system-1 Tue 10 Jan 2023 12:17:37 PM CET

Analyse des Bootvorgangs mit journalctl

• journalctl -b
• journalctl -b | grep “Network driver”
• journalctl -b | grep usb
• journalctl -b -u date1
• journalctl -b -u date2
• journalctl -b -u date3

Erstellen von Timer (Ersatz von cron und at)

Aufgabe 1

• cat /etc/systemd/system/date1.timer

[Unit]
Description=Run date1.service every 2 minutes 

[Timer]
OnUnitActiveSec=2m
[Install]
WantedBy=timers.target

• systemctl stop date1.service
• systemctl start date1.timer
• Wenn der Service noch aktiv ist kann es nicht durch den Timer getriggert werden

Aufgabe 2

• cat /etc/systemd/system/get-octett.service

[Unit]
Description=Get Octett

[Service]
Type=simple
ExecStart=/usr/local/sbin/get-octett

[Install]
WantedBy=multi-user.target 

• cat /etc/systemd/system/get-octett.timer

[Unit]
Description=Get Octett

[Timer]
OnBootSec=10s

[Install]
WantedBy=timers.target