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86e713 Niklas Polke 2026-08-03 20:52:15
Create SYSTEMD
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# SYSTEMD
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SYSTEM Daemon
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Starts and monitors system and user services.
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## Overview
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| Command | Description |
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| - | - |
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| `systemctl status <serivename>.service` | Status of service (active, inactive, enabled, disabled, ...) |
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| `systemctl list-timers <servicename>.timer` | Status of service timer (time since last run, next planned start, ...) |
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| `/etc/systemd/system/` | Directory of self created services |
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## Create timed service
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1. Create service entry
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```bash
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sudo nano /etc/systemd/system/<servicename>.service
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```
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Update Systemd Configuration
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```bash
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[Unit]
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Description=<what the service / called script does>
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# Wants=network-online.target
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# After=network-online.target
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[Service]
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Type=oneshot|simple
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# RemainAfterExit=no
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User=<user for script>
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Group=<group of files?>
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UMask=0002
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Environment=HOME=<home directory>
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ExecStart=<script with absolute path>
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# ExecStart=/usr/bin/flock --nonblock /tmp/<lock filename>.lock <script with absolute path>
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# ExecStop=
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Additional SYSTEMD options
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# [Install]
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# WantedBy=multi-user.target|timers.target
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```
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- wants/after network-online.target mean that this service needs the network to be online
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- Type `oneshot` is for short running tasks like backup scripts, `simple` for permanently running things like server and databases
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- 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
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Add UMask to SYSTEMD
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- UMask means rights that are removed from created files (0002 - remove write rights for other)
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Additional SYSTEMD options
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- Environment could also be directory of python (inside a virtual environment)
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- flock create lock file to prevent different backups running in parallel
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- nonblock means, that additional starts doesn't wait but stop executing
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Additional SYSTEMD options
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- `Restart=on-failure` means restart if service crashed
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- `RestartSec=5` delay for automatic restart
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- `Install WantedBy` tells the service what to do when `systemctl enable` is called
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Update SystemD Timer
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2. Test (only needed, if not started by timer (see below))
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Create SYSTEMD
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```bash
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sudo systemctl daemon-reload
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sudo systemctl start <servicename>.service
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sudo systemctl status <servicename>.service
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```
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3. Create timer
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```bash
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sudo nano /etc/system/system/<servicename>.timer
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```
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```
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[Unit]
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Description=<name and how often as title>
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[Timer]
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OnCalendar=*-*-* 03:15:00
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Persistent=false
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Unit=<servicename>.service
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[Install]
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WantedBy=timers.target
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```
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- OnCalendar sets time for daily start
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- Persistent=true would mean, that if Raspi would be offline during start time, the run will be catched up after the next start
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4. Enable / activate Timer
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```bash
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sudo systemctl daemon-reload
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sudo systemctl enable --now <servicetimer>.timer
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systemctl status <servicetimer>.timer
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```
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- --now starts the timer after enabling
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## List all timers
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`systemctl list-timers` or `systemctl list-timers <servicename>.timer`