Add nm-unmetered-connection checks

etc/systemd/system/nm-unmetered-connection.service

@@ -0,0 +1,7 @@
+[Unit]
+Description=Check if the current NetworkManager connection is metered
+
+[Service]
+Type=oneshot
+ExecStart=/usr/local/sbin/nm-unmetered-connection.sh
+

etc/systemd/system/restic-backup.service

@@ -1,10 +1,11 @@
 [Unit]
 Description=Backup with restic to Backblaze B2
 OnFailure=status-email-user@%n.service
+Requires=nm-unmetered-connection.service
 
 [Service]
 Type=simple
 Nice=10
 ExecStart=/usr/local/sbin/restic_backup.sh
 # $HOME or $XDG_CACHE_HOME must be set for restic to find /root/.cache/restic/
-Environment="HOME=/root"
+Environment="HOME=/root"

etc/systemd/system/restic-backup.timer

@@ -1,7 +1,6 @@
 [Unit]
 Description=Backup with restic on schedule
-Requires=unmetered-connection.service
-After=unmetered-connection.service
+Requires=nm-unmetered-connection.service
 
 [Timer]
 OnCalendar=daily

usr/local/sbin/nm-unmetered-connection.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+
+metered_status=$(dbus-send --system --print-reply=literal \
+       	--system --dest=org.freedesktop.NetworkManager \
+	      /org/freedesktop/NetworkManager \
+	      org.freedesktop.DBus.Properties.Get \
+	      string:org.freedesktop.NetworkManager string:Metered \
+	      | grep -o ".$")
+
+if [[ $metered_status =~ (1|3) ]]; then
+  echo Current connection is metered
+  exit 1
+else 
+  exit 0
+fi
+