First shot at creating a Debian service

Cargo.toml

@@ -10,8 +10,12 @@ license = "MIT License"
 
 [package.metadata.deb]
 maintainer = "Maarten Mulders"
+maintainer-scripts = "debian/"
 copyright = "2021 - 2023 Maarten Mulders"
 
+[package.metadata.deb.systemd-units]
+
+
 [dependencies]
 config = "0.13.3"
 log = "0.4.19"

debian/postinst

@@ -0,0 +1,49 @@
+# Inspired by https://github.com/NLnetLabs/krill/blob/main/pkg/debian/postinst
+
+#!/bin/sh
+set -e
+
+PKG_CONF="/etc/dsmr-rs.conf"
+PKG_CONF_PERMS=640
+PKG_USER="dsmr-rs"
+
+create_user() {
+    if id ${PKG_USER} > /dev/null 2>&1; then return; fi
+    adduser --system --no-create-home --group ${PKG_USER}
+}
+
+create_configuration() {
+    if [ ! -f "${PKG_CONF}" ]; then
+        cat <<EOF > ${PKG_CONF}
+# The DSMR-reader API to forward telegrams to
+DATALOGGER_API_HOSTS=https://my.host.name
+
+# The serial port to read telegrams from
+DATALOGGER_SERIAL_PORT=/dev/ttyUSB0
+
+# The API key to authenticate against the DSMR-reader API
+DATALOGGER_API_KEYS=something-secret
+
+# The input method for reading telegrams. Expected to always be 'serial', so effectively ignored.
+DATALOGGER_INPUT_METHOD=serial
+
+# Baudrate for reading telegrams from the serial line.
+DATALOGGER_SERIAL_BAUDRATE=9600
+
+EOF
+        # Ensure that the config file has the correct ownership
+        chown ${PKG_USER}:${PKG_USER} ${PKG_CONF}
+
+        # Ensure that the config file has the correct permissions
+        chmod ${PKG_CONF_PERMS} ${PKG_CONF}
+    fi
+}
+
+case "$1" in
+configure)
+    create_user
+    create_configuration
+    ;;
+esac
+
+#DEBHELPER#

debian/service

@@ -0,0 +1,9 @@
+[Unit]
+Description=dsmr-rs
+
+[Service]
+EnvironmentFile=/etc/dsmr-rs.conf
+ExecStart=/usr/bin/dsmr-rs
+
+[Install]
+WantedBy=multi-user.target