Add a reboot-required check

check_reboot_required

@@ -0,0 +1,28 @@
+#! /bin/bash
+#
+# check_reboot_required.sh
+# Copyright (C) 2021 Vintage Salt <rehashedsalt@cock.li>
+#
+# Distributed under terms of the MIT license.
+#
+
+rr="/var/run/reboot-required"
+# 604800 - 1 week in seconds
+threshold="604800"
+if [ -f "$rr" ]; then
+	# We have a pending reboot; alert in different states depending on its age
+	lastmod=$(date +%s -r "$rr")
+	now=$(date +%s)
+	if (( now - lastmod > threshold )); then
+		echo "CRITICAL - Pending reboot older than $threshold seconds: $(cat rr)"
+		exit 2
+	else
+		echo "WARNING - Pending reboot: $(cat rr)"
+		exit 1
+	fi
+else
+	# We have no pending reboots
+	echo "OK - No pending reboots"
+	exit 0
+fi
+