add configuration via /etc/default/polkadot

Cargo.toml

@@ -88,13 +88,14 @@ extended-description = "Implementation of a https://polkadot.network node in Rus
 section = "misc"
 maintainer = "martin@parity.io"
 license-file = ["LICENSE", "0"]
-maintainer-scripts = "scripts/deb/"
+# https://www.debian.org/doc/debian-policy/ch-maintainerscripts.html
+maintainer-scripts = "scripts/packaging/deb-maintainer-scripts"
 assets = [
-	["target/release/polkadot", "usr/bin/", "755"],
-	["scripts/polkadot.service", "etc/systemd/system/", "644"]
+	["target/release/polkadot", "/usr/bin/", "755"],
+	["scripts/packaging/polkadot.service", "/lib/systemd/system/", "644"]
 ]
 conf-files = [
-	"/etc/systemd/system/polkadot.service"
+	"/etc/default/polkadot"
 ]
 
 # Configuration for building an .rpm package - for use with `cargo-rpm`

README.md

@@ -25,11 +25,11 @@ Currently supports Debian 10 (Buster) and Ubuntu 20.04 (Focal), and
 derivatives.
 
 Installation from the repository will create a `systemd` service that can be
-used to run a Polkadot node. By default, it will run as the `polkadot` user,
-with no additional flags. The service file located at
-`/etc/systemd/system/polkadot.service` can be edited to customise this as
-necessary. This file will not be overwritten on updating polkadot. Conversely,
-you may also just run the node directly from the command-line.
+used to run a Polkadot node. This is disabled by default, and can be started by
+running `systemctl start polkadot`. By default, it will run as the `polkadot`
+user.  Command-line flags passed to the binary can be customised by editing
+`/etc/default/polkadot`. This file will not be overwritten on updating
+polkadot. You may also just run the node directly from the command-line.
 
 ```
 # Import the security@parity.io GPG key

scripts/packaging/deb-maintainer-scripts/postinst

@@ -0,0 +1,17 @@
+#!/bin/sh
+
+set -e
+
+action="$1"
+config_file="/etc/default/polkadot"
+
+if [ "$action" = "configure" ]; then
+  # Make user and group
+  getent group polkadot >/dev/null 2>&1 || addgroup --system polkadot
+  getent passwd polkadot >/dev/null 2>&1 ||
+    adduser --system --home /home/polkadot --disabled-password \
+    --ingroup polkadot polkadot
+  if [ ! -e "$config_file" ]; then
+    echo 'POLKADOT_CLI_ARGS=""' > /etc/default/polkadot
+  fi
+fi

scripts/polkadot.service → scripts/packaging/polkadot.service

@@ -4,11 +4,12 @@ After=network.target
 Documentation=https://github.com/paritytech/polkadot
 
 [Service]
-ExecStart=/usr/bin/polkadot
-Restart=always
-RestartSec=120
+EnvironmentFile=-/etc/default/polkadot
+ExecStart=/usr/bin/polkadot $POLKADOT_CLI_ARGS
 User=polkadot
 Group=polkadot
+Restart=always
+RestartSec=120
 MemoryHigh=5400M
 MemoryMax=5500M