Commit 86e713
2026-08-03 20:52:15 Niklas Polke: Create SYSTEMD| /dev/null .. linux/systemd.md | |
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| + | # SYSTEMD |
| + | SYSTEM Daemon |
| + | Starts and monitors system and user services. |
| + | |
| + | ## Overview |
| + | | Command | Description | |
| + | | - | - | |
| + | | `systemctl status <serivename>.service` | Status of service (active, inactive, enabled, disabled, ...) | |
| + | | `systemctl list-timers <servicename>.timer` | Status of service timer (time since last run, next planned start, ...) | |
| + | | `/etc/systemd/system/` | Directory of self created services | |
| + | |
| + | ## Create timed service |
| + | |
| + | 1. Create service entry |
| + | ```bash |
| + | sudo nano /etc/systemd/system/<servicename>.service |
| + | ``` |
| + | |
| + | ``` |
| + | [Unit] |
| + | Description=<what the service / called script does> |
| + | Wants=network-online.target |
| + | After=network-online.target |
| + | |
| + | [Service] |
| + | Type=oneshot|simple |
| + | RemainAfterExit=no |
| + | User=<user for script> |
| + | Group=<group of files?> |
| + | Environment=HOME=<home directory> |
| + | ExecStart=/usr/bin/flock --nonblock /tmp/<lock filename>.lock <script with absolute path> |
| + | ExecStop= |
| + | ``` |
| + | - wants/after network-online.target mean that this service needs the network to be online |
| + | - Type `oneshot` is for short running tasks like backup scripts, `simple` for permanently running things like server and databases |
| + | - additional line `RemainAfterExit=yes` would be for things like `mount` which result is *active* even if the service has exited - then also an additional lne for `ExecStop` would be necessary to `unmount` the service |
| + | - flock create lock file to prevent different backups running in parallel |
| + | - nonblock means, that additional starts doesn't wait but stop executing |
| + | |
| + | 2. Test service |
| + | ```bash |
| + | sudo systemctl daemon-reload |
| + | sudo systemctl start <servicename>.service |
| + | sudo systemctl status <servicename>.service |
| + | ``` |
| + | |
| + | 3. Create timer |
| + | ```bash |
| + | sudo nano /etc/system/system/<servicename>.timer |
| + | ``` |
| + | |
| + | ``` |
| + | [Unit] |
| + | Description=<name and how often as title> |
| + | |
| + | [Timer] |
| + | OnCalendar=*-*-* 03:15:00 |
| + | Persistent=false |
| + | Unit=<servicename>.service |
| + | |
| + | [Install] |
| + | WantedBy=timers.target |
| + | ``` |
| + | - OnCalendar sets time for daily start |
| + | - Persistent=true would mean, that if Raspi would be offline during start time, the run will be catched up after the next start |
| + | |
| + | 4. Enable / activate Timer |
| + | ```bash |
| + | sudo systemctl daemon-reload |
| + | sudo systemctl enable --now <servicetimer>.timer |
| + | systemctl status <servicetimer>.timer |
| + | ``` |
| + | - --now starts the timer after enabling |
| + | |
| + | ## List all timers |
| + | `systemctl list-timers` or `systemctl list-timers <servicename>.timer` |